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Author Topic: Kiln temp and humidity logger using the Raspberry Pi platform  (Read 3457 times)

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Offline btulloh

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Kiln temp and humidity logger using the Raspberry Pi platform
« on: December 31, 2017, 02:05:44 PM »
Well, I've gotten started on this thing.  Got the stuff in yesterday.   I can blame ChugiakTinkerer for stirring up trouble.  I hope he gets started on his so we can compare notes.  The weather here is cold and nasty and expected to be like that for at least a week, so this is a good time to work on it.

It looks like the RPi is a good platform to build this around, since the new version already has WiFi and Bluetooth built in.  It does not do A/D conversion, but there are plenty of sensors around with digital I/O.  This thing is more capable than I knew before I got into it a little bit.  It's a lot more than a microcontroller such as the Arduino.  The processor is similar to (or the same as) what's used in some tablets.  Hook a display and a keyboard up to it and it's pretty functional right out of the box once you create a bootable SD card for it.

To start with, I'm using four RTH22 temp and humidity sensors.  They are cheap, but they are not going to be robust enough for long-term duty in a kiln environment.  There are more appropriate sensors available, but these will work for now.

So far the RPi is connected to my wifi and running the GUI that is designed for it.  I also have an app called Cayenne running on my cell phone that is designed as a remote desktop for the Pi and this is working.  (It took some fiddling since my primary wifi network is running a second router set for bridge mode.)

So far I've been able to get one of the sensors wired up and some simple code done to read the temp and humidity on command, so that's a step in the right direction.

My objective is to use three t & h sensors - two inside the kiln and one outside - to log data on a regular interval.  These can also be checked at any time to see what's going on at that moment.  Just for fun I think I'll add a sensor to monitor the intensity of the sunlight and log that as well.  All this could lead to adding fan control somewhere down the road. 

This could all get even more complicated as it proceeds, but that would be normal I guess.

Not a lot of specifics to report at this point, but if someone is interested I'll be glad to share anything I've used or learned as I go.  I'm looking forward to ChugialTinkerer getting started and see what he comes up with.

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Offline ChugiakTinkerer

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #1 on: December 31, 2017, 02:54:56 PM »
It's on, like Donkey Kong!

Okay, I'm running a little behind you.  I was hoping to find an RPi in my stocking but I got coal instead.  I'm probably going to use a Raspberry Pi Zero W for the controller.  It only costs $10 and has the wifi onboard like the Pi 3.

My interest is in a remote monitoring situation, where I'll need a GSM module to connect to the wireless network.  I suspect ultimately I'll be looking at an Arduino (or similar, such as Photon, etc) as a controller because I can dial back power consumption in a big way.  But the Pi will be a handy platform for prototyping, and depending on my final design it could serve as the interface for uploading data to an Internet of Things data service.

Alrighty then, time to shut up and start ordering components!
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Offline Don P

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #2 on: December 31, 2017, 04:57:00 PM »
Good deal, if y'all can document this here and teach at a kindergarten level I'd sure appreciate learning more about how these things work.

Offline WLC

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #3 on: December 31, 2017, 07:40:43 PM »
Yea, I saw Raspberry pie and got hungry.  Yall talking waaaay over my head.
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Offline btulloh

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #4 on: January 01, 2018, 08:08:36 AM »
GSM is interesting.  I looked around and found that GSM service for low-bandwidth data is pretty cheap.  I always wondered about  the cost for those game cams that had GSM capability.  For me, my kiln is close enough to the house (for now) that it's in wifi range, so that makes thing a little simpler.

One of the big challenges for this will be the humidity sensors.  The ones I've looked at will not like living in the kiln environment.  That's going to be especially true when drying white oak, etc.  Not only a sensor problem, but connectors and everything else.  Conformal coating may help with corrosion issues, but the sensor itself may be a consumable item.  It may even require some way of sampling kiln air using a pipe or tube and limiting the long-term exposure of the sensing element.  I don't mind eating a few sensors to find out how it's going to work, but degradation may (or will) affect accuracy.
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Offline btulloh

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #5 on: January 01, 2018, 08:16:41 AM »
Except for the  wifi and/or gsm side of this, the Arduino would be the perfect tool to run the show.  There's really not much overhead in collecting measurements or even storing a few days worth of readings on board.  It would be interesting to see what the power consumption is for both ways.  Probably using the Pi-0 headless is still pretty low on power consumption.  GSM or wifi is going to require more power, but that can be short-term and intermittent.  A very small solar panel/battery should be adequate, but that starts to make the total cost go up pretty fast.  But hey, all in the name of science.  This project could probably qualify for a grant from somebody.  :D

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #6 on: January 01, 2018, 08:32:17 AM »
I hope you get your parts and get started quickly so we can commiserate on the learning curve.  I got out of the gate pretty fast, but now I'm bogged down on development process issues.  Using open-source tools has it's challenges when it comes to documentation, etc.

Right now I'm hung up on making the ide/compiler/linker/assembler happy now that I've gotten past the rudimentary phase.   I do not have any experience in a Linux environment, so that doesn't help.  The RPi has a GUI that makes things a little easier since I can look around and find files and directories.  It also comes with Chromium (a small version of Chrome) and it's nice to be able to do research right on the development platform.  A lot of the examples and documentation I find are references to older versions of hardware/op system/etc.  Things evolve quickly on this RPi platform and there's no real form of document or version control of anything. 

So there we are for the moment.  I better get to work on this before the football games call me away.

Get that stuff ordered!!
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Offline pineywoods

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #7 on: January 01, 2018, 12:59:03 PM »
You guys be sure and keep this thread going. I'll be checking daily. Already have a Rpie and most of the tools. My mill already has a hand-held remote, but it's IR. Suggestion on the humidity sensor. They will be rather delicate and short lived. Why not use 2 temp sensors, one dry, the other with a wet wick. Temp sensors are plenty robust. Send the 2 temp readings to the Rpi and do a table lookup to get a very accurate humidity calculation..
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #8 on: January 01, 2018, 01:01:15 PM »
Stuff is ordered!  The big river will be sending me a Raspberry Pi Zero W starter kit with official case.  It's official, man.  Next thing you know this will go down on my permanent record.

I've been on a Linux desktop for about a decade, been running servers for more like two.  Hopefully some of that experience will carry over to the Pi.  The Raspbian version of Linux is derived from a Debian distribution.  That's become the most widely used distro for desktop systems, and it's what all of my recent Linux use has been based on.  So I'm optimistic I can get up and running quickly.

I ordered some potted Dallas thermistors to play with temperature monitoring.  They look to be well suited for putting in the wood stack and I'm hoping will have some durability.  It's essentially this one, but I ordered from a different vendor that has 3 meter leads.

I got a DHT22 on order as well to do the temp and humidity measurements.  Just one mounted on a PCB, for prototyping.  But it is pretty small so maybe it will fit in protective housing.  AdaFruit sells an encased version, the AM2315.  That runs $30 but looks like it could withstand the mechanical rigors of a kiln environment.  It's durability to corrosion would remain to be seen.  I'm traditionally a cheap SOB and if I can find a DIY way to do it that would be my preferred.  So I'm keeping my eyes out for an old stage microphone that I can get for almost free then drop a sensor into.
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Offline btulloh

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #9 on: January 01, 2018, 01:18:51 PM »
pineywoods:  Good suggestion on wb thermo.  Should be more accurate and solve deterioration issues.
What language are you coding in?  I'm using the Geany IDE with GCC compiler that came with the Raspbian distro.  That's all fine, but I'm not getting my environment set up correctly or something when I start using some functions and headers that came from outside sources. ??  Fighting with that for the last 24 hours now, with a little time off for bad behavior.

CT:  Good going!  Can't wait till you get started.  I think your familiarity with Linux will be a big help.  My lack of experience with Linux is one more obstacle.  Not too bad though.  I find myself blindly following instructions without understanding the whole picture.  Uncomfortable.

I would stay away from the DTH22 if I was doing it again.  It's not a very good device, except for being cheap.  It doesn't hurt to use one for testing, but it's a bit more of a pia than something that's I2C based communication.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #10 on: January 01, 2018, 01:23:29 PM »
@ pineywoods,

That might be a more robust means to measure relative humidity.  It's definitely something to look into.  Just some quick internet searching shows folks are looking at ways to simplify that calculation for an embedded device application.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #11 on: January 01, 2018, 01:24:29 PM »
By the way, the fancy housing and screen on that Adafruit sensor will not keep the corrosive stuff away from the sensor.  From what I've read so far, most (or maybe all) of those humidity sensors seem to be alergic to long-term exposure to extreme heat and humidity.  I think pinewoods wet-bulb suggestion could be the ticket.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #12 on: January 01, 2018, 01:35:00 PM »
Regarding Linux, I have to say that I'm warming up to it.  Even at this early stage I'm starting to appreciate its benefits.  I'm just not sure how many more things I have time to learn from the ground up.
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Offline pineywoods

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #13 on: January 01, 2018, 02:03:57 PM »
@ pineywoods,

That might be a more robust means to measure relative humidity.  It's definitely something to look into.  Just some quick internet searching shows folks are looking at ways to simplify that calculation for an embedded device application.
No need to do calculations. Table lookups are easy to code, and I'd bet WoodDoc could quote you a table right off the top of his head.
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Offline btulloh

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #14 on: January 02, 2018, 08:04:53 AM »
Here's a library for the DHT11/22 sensors: https://github.com/adafruit/DHT-sensor-library


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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #15 on: January 02, 2018, 12:50:26 PM »
Got my issues sorted out.  15 years of rust plus assumptions plus open-source tools make for a bad combo.

Makefile issue resolved and I'm back on track now. 

No need to do calculations. Table lookups are easy to code, and I'd bet WoodDoc could quote you a table right off the top of his head.


Excellent point. 
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #16 on: January 02, 2018, 01:04:33 PM »
So what pushed you guys towards the rasberry pie vs the arduino? I was thinking about arduino for my sawmill setworks. The solar kiln will come later but still looking at everything trying to learn and figure out how I can integrate everything.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #17 on: January 02, 2018, 01:43:51 PM »
The RPi has a lot more horsepower than the Arduino.  The arduino is a microcontroller and well suited for embedded systems.  The RPi has enough juice to host it's own development process.  With a display and keyboard, it's basically a computer. 

The Arduino would certainly be able to do all the temp and humidity logging and display it.  The RPi has ethernet, wifi, bluetooth, and hdmi ports built in, so it will connect up to your network right out of the box and can be used to report data, etc over your local network or to the cloud or to North Korean hackers.

Your project may fit either one, it may be more well suited to one or the other.  The setworks project will have more i/o to deal with than the kiln logger, but it will also benefit from a real-time oriented platform (which I think describes the Arduino.)

I'm not familiar enough with the Arduino to fully answer the question beyond that.  I think C-Tink has more experience with them and can elaborate.  (In fact, I jumped on the RPi because of his post.)



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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #18 on: January 02, 2018, 10:45:50 PM »
I have no experience with either Arduino or Rpi, but I've been eyeing both for a while now and this project gave me an excuse to try it out.  I like the onboard wifi in the latest RPi boards and the fact that I can put an entire OS on one.  It will give me much flexibility as I explore how to upload data to an IoT service and at the same time host a local web server for showing temp data, etc, on my home wifi.

To be honest it's probably because the Raspberry Pi is essentially a computer so it will likely be an easier transition from the programming I've done on a desktop system.  The Arduino seems more like working without a net.  I'll likely end up there with the weather monitoring system I want to put together, but I gotta learn to crawl first.

Plus everything btulloh said.  8)
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #19 on: January 03, 2018, 07:31:26 AM »
Thanks for taking the time to do this. I am really excited for the continued updates. Speaking of that I need to do the updates on my build.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #20 on: January 03, 2018, 08:54:21 AM »
This RPi3 is indeed a little computer and quite a thing for it's price and size.  It starts up with a windows-like desktop and enough applications to do some real work.  It comes with a light version of Chrome and some MS Office style applications for docs and databases and what not.  Plus it has a lot of the development tools on the distro and is ready to rock right out of the little box.

I am also running an application call VNC Server on it that allows me to use a remote desktop on another PC to do the work remotely, or in my case from a more comfortable chair.  VNC works pretty well and is pretty fast so it feels like you're on the native machine.

It is kind of nice to do the development work right in the environment that's going to be used for the finished product.  Here's a screen shot of the RPi desktop with a browser, and IDE, a file manager, and a terminal window open:

 

 


If you know Linux it's a breeze.  If you don't know Linux, it's still a zephyr.  Linux is quite nice and I wish I had gotten familiar with it earlier.  All in all, the little 35$ Raspberry Pi is a nice little platform.  If you use the Pi 0, it's only ten bucks and has almost as much capability.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #21 on: January 03, 2018, 10:01:42 AM »
Friend of mine just said the 8622 I think the model was is only $2
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #22 on: January 03, 2018, 10:42:38 AM »
That may be.  I'm not in a position to provide much help on that.  I probably have a total of about seventeen minutes studying Arduino capabilities, and not much more than that on the RPi.  You may end up with both.  The cost of that part of a setworks-type project will be trivial compared to sensors and actuators and switches and displays and stuff.

From what I've seen, the Arduino seems better suited to real-time, embedded systems type work.  Hopefully it has better ways to handle things like PWM and the PID libraries needed for controlling something like a sawmill head.

I think pineywoods has been there, done that.  He was replacing the replacing the brain I think,  with all the control and feedback in place already.  You'll be  starting from scratch, so it will be challenging.  It will be interesting to follow your progress and see how it all shakes out.  Hey - winter is a good time for this kind of thing.  You don't really need to have your mill finished to get started!!  Go for it!!!
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #23 on: January 03, 2018, 10:51:30 AM »
I already have random stuff here at work to play with. I should start doing that.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #24 on: January 04, 2018, 11:46:20 AM »
Chipping away at it.  Got all three t/h sensors hooked up and reading.  Working on setting up SQL database and time management.  Then it's just a matter of uploading data on periodic basis to one of the free db servers.  I also want to be able to check current data with cell phone.  All of these things are pretty straightforward but take a little time to get done.

I also have to get some real sensors to use inside the kiln and work on the wet-bulb thing.

At some point I'll need to figure out enclosures and wiring plan.  Right now it's just a science project.

 

 
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #25 on: January 04, 2018, 12:11:42 PM »
Readings

 

 
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #26 on: January 04, 2018, 12:13:26 PM »
Hard to read.  Oh well.  Just a bunch of numbers and timestamps.  Trying to adhere to the FF "post more pictures" rule.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #27 on: January 04, 2018, 12:21:00 PM »
Does that export to excel or csv?
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #28 on: January 04, 2018, 12:37:00 PM »
It can be put into a csv file instead of going to the screen.  Probably better to put in a database and let SQL handle the overhead. 

Basically the data can be anything you need it to be.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #29 on: January 04, 2018, 01:05:08 PM »
thats great if you know SQL. I dislike it and it hates me :)

However, I am a master with excel.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #30 on: January 04, 2018, 01:11:08 PM »
 smiley_clapping

Looking good!

Meanwhile, back at the CT ranch, I'm still waiting for my goodies to ship.

For those reading unfamiliar with the CSV format, it's simply a text file with values separated by commas, hence the file extension abbreviation: Comma Separated Values.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #31 on: January 04, 2018, 01:22:26 PM »
It can be done any way that suits you.  That's the good thing about doing this.  I'm not adept in SQL either but I can pick my way through a simple thing like this.  I think it's the easiest way (for me) to get data stored, then put up into the cloud, and then retrieve it.  Then I'll put it into Excel too to use it.  It's just personal preference.  I think it will be the easiest and quickest way for me to get to the ultimate goal.  I may also be wrong about that.  :D
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #32 on: January 04, 2018, 01:44:43 PM »
google drive and google sheets may be something worth looking into for that? Or maybe java? I forgot you want to view it on a website.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #33 on: January 04, 2018, 01:52:49 PM »
Those too. 

These days there are many ways to skin this particular cat.  I guess that's the  good news.  At some point it comes down to grabbing a weapon and joining the battle.  But when it's time for the battle, you need have picked out your weapon.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #34 on: January 04, 2018, 05:18:38 PM »
If you want a formula for calculation of RH from DB and WB, see
http://maxwellsci.com/print/rjaset/v6-2984-2987.pdf

If you want formula EMC values, see the Wood Handbook (2010 edition), equation 4.5.

For a complete table, see DRYING HARDWOOD LUMBER, about page 15.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #35 on: January 04, 2018, 05:56:06 PM »
Thanks Doctor Gene, that's very helpful.  The document you reference is directly relevant to this task.  Now we have the info needed.  That makes this a productive day!!
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #36 on: January 05, 2018, 08:01:05 AM »
Starting to work on the data file and cloud storage today.  The more I look at alternatives and work on the implementation I'm starting to think that a simple CSV format will be the better solution.  It will become more clear as the work progresses.

Interesting Arduino boards with built-in wifi:

https://smile.amazon.com/gp/product/B01IK9GEQG/ref=pe_2518910_267133250_em_1p_6_ti

https://smile.amazon.com/HiLetgo-Internet-Development-Wireless-Micropython/dp/B010O1G1ES/ref=pd_bxgy_328_2?_encoding=UTF8&pd_rd_i=B010O1G1ES&pd_rd_r=6A4555HBFEQNFHBFZAEK&pd_rd_w=ykKCK&pd_rd_wg=evdaz&psc=1&refRID=6A4555HBFEQNFHBFZAEK

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #37 on: January 05, 2018, 08:11:16 AM »
I talked to an electronics guy here at work and he felt that for kiln monitoring the raspberri pi was the best option but for the simpleset I want to do definitely need to do arduino.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #38 on: January 05, 2018, 09:27:36 AM »
You're fortunate to have easy access to someone like that.  I don't think there is a wrong choice.  I wish I had time to get an Arduino and do it BOTH ways.  I've only got another week that I can focus on this before I have to move on to another commitment.  It's gonna take me that long long just to get these particular worms back in the can.  Maybe longer.  Yesterday I should have had 8 hours of undivided attention to this and it turned out to be about 30 minutes.  Today I'm hoping to put more time on it. We'll see.  I have it reading the sensors on a schedule now and I'm working on the data collection and cloud storage.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #39 on: January 05, 2018, 09:33:25 AM »
Sweet. at least you are making progress.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #40 on: January 05, 2018, 02:05:05 PM »
While I sit on my thumbs waiting for my electronics, I've been thinking about how to house the device.  But for the wifi aspect any old enclosure would work.  One made of steel will kill the radio signal instantly, as will anything that is too conductive.  I suspect any plastic, abs, polypropylene, or fiberglass enclosure will permit enough signal to allow decent data transmission.

I would want it to be big enough to allow mounting a 120v outlet in addition to the RPi and associated circuitry.  I'm visualizing something like the box containing my telephone service entrance, but my google-fu has been weak in finding something that fits my criteria perfectly and doesn't cost $100 plus shipping.  I suspect a visit to the local Re-Store will be fruitful.  Anything weather resistant and roughly 12x12x4 should do the trick.

Assuming the enclosure is mounted on the wall of the kiln, I would run cabling for the sensors though the kiln wall into a waterproof junction box inside the kiln.  If at all possible I would have the junction box inset so that it is nearly flush with the interior kiln wall to minimize opportunities for it to be damaged during loading and unloading.

Once the kiln is loaded, the sensors would be placed either in the stack or on the wall and connected to the junction box with either a mil-spec connector or a trailer/RV connector.  Price and suitability for kiln temperatures would drive that selection.  I can see having three temperature probes set up on a pigtail about 6' long.  One probe would be inserted into a board in the stack.  The other two would be clipped to the wall, with one of the probes having a wick and reservoir for wet bulb temperature.  Just before closing the door the pigtail would be inserted into the socket on the junction box.

One could skip all the junction box and connector mess and just wire the sensors direct to the RPi.  During unloading and loading the sensors could be coiled up hung out of the way on a conveniently placed Velcro strap.  This way would be less costly and less complicated.  But I have no clue which would be better in a given kiln.  I think at the very least there should still be a junction box inside the kiln, for when a sensor needs to be replaced.  If one had to thread a cable through the kiln wall every time a thermistor failed it would probably motivate the owner to put in a junction box anyhow.

Those are my thoughts.  Any of it sound helpful for your existing or future operations?

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #41 on: January 05, 2018, 02:14:37 PM »
I like a common junction box as a pass through. makes running wires and anything else in and out easy. The real trick is keeping it clean dry and the insulation loss in that area.

Would it make more sense to come through the roof? hanging wires be less likely to get ripped out or damaged if walking around in there.

there are also some mil spec wire connectors that have a ton of leads. that would be the ultimate setup. 1 plug to plug in all the stuff inside the kiln. When not in use unplug and put in storage place. then the only thing you would have to worry about inside the kiln is the plug and the wires.

Search mil spec ip69k connector. gives you lots of options. Make sure if you go this route you specifically find IP69K rated connectors. That is waterproof dustproof all the good stuff.

here is a good reference for IP ratings
https://www.averyweigh-tronix.com/News/news-and-case-studies-by-product/indicators-news-and-case-studies/what-is-the-ip-rating-system/
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #42 on: January 05, 2018, 03:52:32 PM »
My first thought was to look for a suitable plastic NEMA box.  They even have a few to choose from at HD or Lowes, or any electrical distributor for more choices.  Two plastic conduits through the wall of the kiln from the back of the box which would be mounted on the north wall somewhere.  I plan to mount two temp sensors inside - one in the collector area and one at the outflow of the lumber stack.  Maybe two wb thermo's at the same locations or maybe one wet bulb - TBD.   Put one DHT22 outside for reading ambient t&rH.  The main detail to be worked out is proper isolation/insulation for the relay board on the HV side of things.

Progress:
- Now storing CSV data in a file. 
- Looking around at various free IoT server options for moving data to the cloud.  There are options out there, just trying evaluate and make a choice.  Already signed up for thingspeak.com, but so far not excited about how they work.  Or I haven't found what I'm looking for on their service.

CT - I hope you get your goodies soon.  I have to order some temp sensors and a relay board.  I haven't decided on the best temp sensor to use.  I'm interesting to see you yours does.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #43 on: January 05, 2018, 08:44:32 PM »
Still no joy with Amazon.  I'm headed out to the property for the weekend.  If it hasn't shipped by Monday I may cancel and go with someone else.

Thanks for the link on the NEMA connectors.  My first thought was that IP69k would be overkill, but the 9k aspect protects against high temperature spray so should hold up to the heat of the kiln.  Right?  say_what
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #44 on: January 05, 2018, 08:50:04 PM »
That was my thought and the reason for the recommendation. The other reason for that is you can drill a 1/2" hole in the kiln for the wire to pass through and then mount a plate with the connector inside. if you seal the wire it will be very little if any leak helping to keep the kiln better. Then all you need to do is take your full harness and plug in in after all the sensors are located where you want them.

I am all about doing things the easy / lazy way. This will also make wire runs quite a bit cleaner if done right.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #45 on: January 05, 2018, 09:44:13 PM »
I'm just going to run some plenum rated cable from the terminal block outside (inside the box with the brain) to the sensors. The sensors will be soldered on.  No connectors.  It's not quite that bad in there - it's not the surface of Venus.  The a/c wiring inside my kiln is EMT and regular duplex outlets and they're doing ok. 

Like the old saying goes: "it's not the heat, it's the humidity".  Plus some noxious gasses from the oak, etc.  I'm going to consider some of those things inside to be consumable.  Heck, the kiln itself only lasts about, 10 years I'm told.

The inside of the kiln is not a neat and tidy environment except for the day you finish building it.  In operation it's never completely closed up either - the vents are cracked open just a bit.  It's supposed to be pretty tight, but not like a submarine.  At one time I thought it should be air-tight to a depth of 20 fathoms, but I learned otherwise.  I guess we build 'em as tight as we can because there still be will be a few air leaks here and there anyway - and then we crack the vents a bit.

Anyway, that's just my approach to the wiring thing.  Low cost, a little bit rock and roll.  Not exactly Mil-spec.  But effective and dependable.  Rev B might be stepped up a little if there needs to be a Rev B.

That's just me.  Everybody builds to suit themselves.  (That's the benefit of my no longer being in the manufacturing biz.)

By the way CT, that seems odd for Amazon.   FYI mine came from Amazon (prime) and they didn't show as SHIPPED until very late the night before they were delivered, on time.   (There is a distribution center here though.)  It seems like the movement between Amazon facilities does not show up in the tracking detail.  Or maybe they just messed yours up.  I hope not.  I'm hoping you get your stuff so you can get started.

===

Not sending data to the cloud yet, but local file writing is doing fine. 

Nosed around on Thinkspeak a little and it may be OK.  TBD

I got sidetracked trying to setup SAMBA on the RPi so I can see it on the Windows network.

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #46 on: January 06, 2018, 09:26:41 PM »
Using ThingSpeak.com for cloud storage for now.  Got my application connected and uploading static test data on regular intervals, so that's progress.  I need to hook that process up to the sensor reading process and then I'll have something that is pretty close to the finished deal. 

On another front. the RPi is now able to connect to my Windows network.  I can access network devices from the RPi but so far I can't see the RPi from a Windows machine on the network.  I'm still trying to configure Samba to make that happen, but it's not a major concern at the moment.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #47 on: January 07, 2018, 03:16:48 PM »
Finally got the sensor data going to the cloud in real time.  It's a good milestone.  It's viewable at https://thingspeak.com/channels/398226.
This is just test data, taken from three different t/rH sensors in my home office.  One is room temp, one is the temp of the case opening of the RasPi, and the third is sitting directly over a radiator.  The charts are not very useful - they're just the default charts that come with a new channel page.  They will be replaced with something more useful later.  I have the updates going out pretty rapidly for now, just to speed up the testing process.  I will plan to update the readings every 15 minutes when this is installed in the kiln.

I need to do some housekeeping and cleanup work on the existing code, but it's functioning pretty well at this stage.  It's about time to order some different sensors and start working on the wet-bulb readings.

Thingspeak.com is owned or run by Mathworks, the company that makes Matlab.  I see where they have functions for dewpoint/rh/wetbulb conversions.  These may be of some help in the rH calcs.  To be investigated. 

I have very little experience with Matlab.  Maybe CT, or somebody is fluent in Matlab.  That could be a good thing.

I suppose ChugiakTinkerer is off-grid this weekend.  Maybe his Amazon package will be waiting for him when he returns and he'll get started.

When it warms back up tomorrow I plan to take this RPi outside and test its wifi range.  Hopefully it will be sufficient. 
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #48 on: January 07, 2018, 06:52:08 PM »
looking pretty sweet. I wish I knew more about matlab. all I know is it is installed on my pc at work.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #49 on: January 08, 2018, 02:14:23 PM »
Amazon sat on my order for a week, so I just canceled it this morning.  Placed an order with SparkFun for an RPi 3, two DS18B20 waterproof sensors, and a BME280 breakout board for temp/pressure/humidity.

My limited exposure to Matlab was when I was in grad school.  It ran in DOS and needed a math co-processor, which I didn't have.  My advisor had it on his office system, and I have a vague recollection of making some nifty 3D graphs with it.  Something tells me my experience won't be very helpful in this day and age.

We spent the weekend at Lake Louise opening a trail to our property.  Our place is 10 miles from the lodge, and only the first half it had trails established.  So Saturday was spent breaking trail in about 3' of loose snow.  Starting out Saturday morning there was fog on Lake Louise.  I could just make out four caribou, and this is the best I could do with my phone:
 

 

We broke trail for about 4 hours and got within 1/4 mile of our place and ran into overflow on our lake.  I was able to power through the worst of it and only got stuck in wet frozen snow with thankfully no standing water.  By the time we extricated ourselves the sun was going down so we headed back to the lodge.  I neglected to take any pictures, but this thread on Trapperman shows lake conditions about like mine. https://trapperman.com/forum/ubbthreads.php/topics/4368161/Re:_Advice_on_getting_snowmobi#Post4368161

On Sunday we were able to make it to the property.  I have a temporary structure up, a Hansen Weatherport as shown below.  Everything looked great, no visits from bears or squirrels.
 

 

Back on topic: SparkFun sent an email confirming my order, so Yay! for modern commerce.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #50 on: January 09, 2018, 08:50:38 AM »
Glad to hear your goodies are finally on the way.

Thanks for the pics from the lake property.  I guess I shouldn't complain about snow and cold weather we have here. 

By the way - DON'T install Cayenne on your Pi!  (I mentioned Cayenne app earlier - it can control the Pi from your cell phone.)  It is not well designed and wastes resources - even when you're not connected.  It is also hard to get rid of.  smiley_devil

I hope your package gets there soon.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #51 on: January 09, 2018, 09:05:54 AM »
Thursday I should be receiving some DS18B20's and a relay board.  I need to come up with a proper wick and reservoir to make the wb thermo.  I wonder how you keep the reservoir from freezing during cold weather?  The wb doesn't need to function below freezing, but it needs to survive without baby sitting.

Today I should be able to test the wifi range.  My kiln is pretty close to the house and well within range for my cell phone, so I'm hoping the Pi will be fine.  I've seen where people have installed an external antenna, but that's just another project.

HD has 12x12x4 plastic NEMA box in stock which should be fine for an enclosure.  I'll need to work out some ventilation issues.  We'll see how that goes.

Uh oh - thinking again.  Danger!  It's certainly possible to rig up something on the Pi to take resistance measurements.  And do some calcs.  And look up things in charts.  And compute moisture content.  Is this crazy?  Is there enough data available to build in a viable wood moisture content monitor?  And . . . maybe some load cells to weigh kiln samples.  ??  Whoa Nelly!  Calm down!



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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #52 on: January 09, 2018, 09:22:24 AM »
no, no, don't stop. Keep going :)
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #53 on: January 09, 2018, 11:19:51 AM »
 :D :D :D

I saw somewhere that cotton shoelaces make a good wick.  They are certainly affordable.

You could also hook up an ultrasonic transducer and measure the time it takes to bounce a signal off the end of your stack of lumber.  An increase over time means the stack is shrinking, yet another indicator of moisture content... 8)
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #54 on: January 09, 2018, 11:22:13 AM »
if your gonna use size could always use laser measure :)
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #55 on: January 11, 2018, 04:27:09 PM »
I've been trying to catch up on chores and running errands for a couple days.  Not much work getting done on the data logger.  A little, but nothing too exciting.

Today I got some more sensors and stuff.  Five of the DS18B20 waterproof thermos, a light level sensor, the relay board, and some terminal strips to help with the wiring.  I have add some things to the software to support the new sensors and relay board.  The biggest task is to get the Pi mounted in an enclosure and wire it to the terminal strips, then install it all in the kiln.

CT - I hope you get your package soon. 
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #56 on: January 12, 2018, 02:20:29 AM »
Nobody loves me.  My order with SparkFun doesn't appear to have shipped yet either.  I'll try a call on Friday to see what's up.

It's busy season at the property.  Even if my goodies arrive tomorrow I probably won't get much done this weekend.  Going to take advantage of the three day weekend and get some work done on my guest cabin.  Or clear some trees.  My wife wants to go to town on the trees at the site where we want to put the main cabin.  So we'll see what the boss wants and go from there.   8)

I may surprise her with a battery-powered chainsaw, if I can find one in stock in town.  So not much progress likely on the electronics front.

UPDATE: I called SparkFun and they apologized for the delay, apparently my order got put on hold by accident.  They upgraded me to priority shipping, so hopefully it arrives soon.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #57 on: January 14, 2018, 09:20:39 AM »
That's got to be frustrating.  Getting your stuff shouldn't be the hard part of the project. 

In the meantime, maybe you could do some poking around in the IoT server world.  I'm using ThingSpeak.com currently, but I'm not convinced it's the best choice.  There are plenty of options out there, even for free.  Amazon (AWS), Google, and many others.  It's a bit of chore just to figure out who offers what and what the specifics are from one to the next.  ThingSpeak is limited to 8 data fields, plus I don't really like the lack of choices on setting up the screen.  Plus some other limitations.  Not bad, but there must be better options.

I'm working on wiring right now.  Not that interesting, but important.  I'm making a breakout for the GPIO to terminal strips that can accommodate  all the sensors.  There are some off-the-rack solutions out there, but I don't have them and I don't really like any of them any way.  Ultimately I will probably make a PCB specific to this project.

I have tested the DS18B20's and they work well.  I'm going to integrate the code for them into the project today. I haven't worked on a wet-bulb setup, but that's on the agenda.  I'm thinking the math won't be that big of an issue in the Pi environment, but I'm not quite clear on whether some of the inputs to the equation are constants or not.  If they are all constants, it's doable.  If they are not constants, then how can a chart be accurate unless the only variables are wb and db? 
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #58 on: January 14, 2018, 02:44:26 PM »
Guys, I think that this is a very cool project, and have a suggestion for you to consider.

For years I have felt that there were some significant improvement opportunities in managing the lumber drying process for small operators.  The oven dry sample board method is unquestionably very accurate, but it requires time.  Traditional pin type moisture meters are not accurate above FSP, yet most of the damage that can occur during the drying process takes place above 35% MC.

What I think that significantly improve the accuracy of the KD process is to add a system to measure the weight of your kiln carts (or stacks) as they dry.  Compression load cells are readily available that can provide input measurements to your Aurdino or Raspberry Pi systems and by incorporating in weight measurements into you kiln management systems you can use your RaPi controller to change kiln settings as necessary in order to achieve a targeted daily drying %.

If you start with a known board footage of your kiln load, you can determine how many lbs of water you want to target for daily removal and manage the drying process accordingly.  You can then calculate the MC% of the lumber based upon it's weight, and automatically change the temp and RH% based upon the actual MC% of the lumber.

To me, this would be the next step in the evolution of kiln drying methods.

Scott
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #59 on: January 14, 2018, 04:25:03 PM »
That is an interesting idea.  Thanks for bringing it up. 

It would not be hard to manage the data from the load cells.  Setting up a kiln with load cells could certainly be accomplished, especially if you baked it in at the construction phase.  It would take some design and engineering, but not too overwhelming. 

The hardest part would probably be establishing the weight of the lumber pack itself minus the pallet, stickers, etc.  All of that is possible.  I guess the thing to determine is whether the benefit is worth going through all that.  Hopefully this will start a good discussion.  I'd love to play with some load cells. 

Looking forward to hearing from others about this.

(If this was about grits, there'd be 50 replies before dark tonight.   :D)
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #60 on: January 14, 2018, 04:35:31 PM »
In the background I have been thinking about using some load cells to keep track of sample boards in the kiln.  This also presents some challenges.  I didn't want to spend too much time on that because it's outside the scope of the original project.  (Feature creep.)  If it starts a lively discussion though - GREAT!

Would monitoring the whole pack be better?  Easier to implement?  If monitoring samples only, how could you do that if they are in the pack?  Can you treat the whole lumber pack like a sample?  Can you get enough data about the pack before it goes in the kiln to make it meaningful? Beats me.  Jump in.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #61 on: January 15, 2018, 07:37:34 AM »
I would make a rail system on the floor for the carts to sit on and roll in and out. Put 4 load cells under the rail system. Measure all your lumber carts or pallets and mark the weight on them. When everything is placed in the kiln it will roll in on the rails real nice and you will get your weight measurement. Then the rest is in the programming.

Here is the real question. What would be the most accurate way of measuring?
Weight
Size
Pin type gauge
all of the above

With the pi it won't be hard to add all of this just going to take a little more time and money. If it was me I think I would want all of it. But I work in an industry where more data is better. The crazy thing is if you add all those sensors you could add a little more and make the kiln 100% automatic.

even if you did not do a rail system you could do 4 pads with load cells and just set your skid on that.

This has been my random convoluted mess of ideas in no particular order. Thankyou. please drive through.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #62 on: January 15, 2018, 09:45:58 AM »
Can you purchase load cells that have the range required to handle the weight of the stack of lumber? I looked online yesterday and I only found some units that handle about 200 lbs.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #63 on: January 15, 2018, 09:52:50 AM »
you can buy truck scales that will more than handle a full load. they are the same load cells with more stuff around them. they come with 4 or 6 pads to.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #64 on: January 15, 2018, 09:53:35 AM »
ouch truck scales are expensive.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #65 on: January 15, 2018, 06:02:56 PM »
It's possible to get the load cells.  That's the easy part.



I was expecting a little chatter about this from some of the experts.  Perhaps that means it's a cure for which there is no known disease.  Maybe there is no reason to look beyond existing methods.  Or maybe it's just they haven't been on the forum for a while.  In any case, it's been pretty quiet on this thread.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #66 on: January 16, 2018, 02:11:17 PM »
I started working on the wet-bulb setup.  My first wick was not effective.  Need to get better a wick.  I do think the waterproof'd DS18B20 will work well for wb.  To be continued.

-- Got the light sensor working correctly on the I2C bus.
 
-- Now there are four DS18B20's and one DTH22 hooked up and working on the test rig.  That is the configuration I'll use when I install this thing in the solar kiln.

The biggest job ahead is to get this installed and wired in the kiln.  Plus the wb/db calcs to get the kiln humidity reading.  Weather is not really cooperating with outdoor work and kiln installation.  I'm going to be accumulating the necessary items for installing this thing and continue to work on the wet bulb setup.

I know all this is not needed to operate the solar kiln, but I am interested in tracking the data - just for science.  Having the ability to easily check temp and humidity will be very handy as well.  Plus I get fan control as a nice side-effect.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #67 on: January 16, 2018, 03:41:04 PM »
Could you use the same material that is used for kerosene lamps?
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #68 on: January 16, 2018, 04:34:34 PM »
How do you get the evaporative cooling on the wb when the fan is off?

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #69 on: January 17, 2018, 08:47:17 AM »
Ron - The wick needs to be tubular.  Lamp wick material may be ok, but it needs to encase the sensor.  I may have to break down and buy some real wetbulb wick.  Not hard to find, it's just not laying around the house right now.  I see people using cotton shoelaces, but apparently the shoelace I used had the wrong fiber content.  I'm sure the nature of the wick affects the accuracy of the measurement.

Don P - That's an important question.  Evaporation still occurs with no air movement, but the rate will change.  My experience with wet-bulb thermos is pretty limited and consisted mainly of taking a reading and looking at a chart.  This is my first go at making one and using it in a kiln.  It may need to be put in a housing and aspirated to get consistent measurements.  I have to do some research, unless somebody jumps in here with the answer.  Ugly weather here today.  Good weather for research.

Initially I'm going to put one of these DHT22 devices in the kiln as well, which measures both rH and temp.  It will probably fail or deteriorate, but it gives me something for comparison. Deterioration will be more of an issue than complete failure of the device.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #70 on: January 19, 2018, 02:09:29 AM »
Got my goods today.  Now to play catch up!
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #71 on: January 19, 2018, 08:28:01 AM »
 8)   smiley_horserider   Good deal, CT.  I'm looking forward to seeing your progress now that you have your stuff.


Got some nice weather coming this weekend.  Time to start installing this thing in the kiln.  I haven't done anything more with the wet bulb thermo.  For now I'm going to put the allegedly fragile DHT22's in the kiln.  I can always work on the web-bulb setup as time permits.  The kiln is empty right now, so it's a good time to do the wiring.  I decided to use a plastic power tool case to house the RPi and whatnot.  I have a good selection of them, since everything you buy seems to come with a molded plastic case.  One of them will be just right.  And free.  Maybe by next week it will all be setup and gathering actual data on the kiln. 

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #72 on: January 22, 2018, 02:17:47 AM »
I've got Raspbian installed and started some very basic circuit building and programming in Python.  I was able to at least turn an LED on and off as shown below.



I've got a DS18B20 waterproof temperature sensor wired in as well, but I'm not seeing it in the W1 bus.  The problem I seem to have is that I did not purchase any 4.7k resistors.  The one in center foreground trying to be a pull-up resistor is only 330 ohms.  As I type this I realize it almost sounds like I know what I'm talking about.  If that's the case it's only because there are some very thorough tutorials out there.

I'm going to swing by Frigid North Electronics tomorrow and pick up those resistors as well as a new soldering iron.  I've got to do a little prep work on the BME280 sensor before I can use it.  Need to solder in a header on the wee little breakout board.  With the state of my vision I'll pick up a magnifying third hand helper station too.

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #73 on: January 22, 2018, 08:50:19 AM »
You're on your way.  Those BME280 sensors are interesting.  I wish I had gotten some of those.

When you get the proper pullup resistor you should be fine. 

I started wiring and installation in the kiln.  Nothing too exciting to report, just wiring and drilling holes.  I re-wired the fan outlets to switch them with the relays and got the a/c out to where the box with the Pi will be mounted.  Not interesting enough for photos.  Most of the weekend was spent catching on up chores outside since the weather was so nice. 
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #74 on: January 22, 2018, 05:14:23 PM »
Back in about 1975, I developed a load cell weighing system that weighed an entire pack of lumber using load cells.  The main issue was the long term drift of the cells, so we did rezero every few days. The system had an automatic kiln temperature system based on load cell info.  The control system used proportional, rate and reset.

Prior to that, Delmhorst had an automatic system using two sets of pins driven to different depths, called the Kiln-Mo-Trol.  They have an updated version now.  It works well indeed.

Prior to that, the Moore Dry Kiln Company had a system called a Kiln-boy.

Subsequent to 1978, Bob Little at the University of TN developed a system that weighed the individual kiln samples.  The weighing system again had long term drift and temperature issues.  Also Lignomat developed a computerized system using pins.

Since that, many others have approached this problem of getting MC of selected pieces in a load.  I saw one where the sample was hung on a wire and the wire ran up and outside the kiln so the load cell was outside the kiln.  Kiln schedules are based on the wetter lumber and not the average, so weighing a pile is not sufficient.

After many tries, including measuring the energy input and measuring temperature drops, the best system we have still involves individual sample selection and weighing.  Once on the scale, computers are used to calculate MC, determine drying rates, establishing correct kiln setting$3so the job of using kiln sample boards is pretty easy now, with just a few minutes of labor each day.

Note that very precise MC is not usually required in lumber drying.  Further, most of the time, precise temperatures and humidity is not required.  Further, almost all defects occur at high MCs, so fancy controls for air dried lumber are a waste of money as they do NOT improve drying quality or time.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #75 on: January 23, 2018, 10:05:45 AM »
That's useful information Gene.  Thanks for weighing in.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #76 on: January 23, 2018, 03:09:28 PM »
Gene, thanks for the insight.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #77 on: January 23, 2018, 10:00:04 PM »
I have been asked to explain this paragraph from above in more detail...
Note that very precise MC is not usually required in lumber drying.  Further, most of the time, precise temperatures and humidity is not required.  Further, almost all defects occur at high MCs, so fancy controls for air dried lumber are a waste of money as they do NOT improve drying quality or time.

To run a kiln using moisture content, we use the average of the wettest half of the samples.  Even then, the schedule does not use decimal points when referring to MC, so 1/2% MC will work.  It is only in getting the final MC that we do try to be more accurate sometimes.

The schedule temperature for air dried can be plus or minus one or two degrees and the humidity within 5% RH during much of the schedule.  We are somewhat concerned about overdrying, so we do try to get the correct humidity at the final stages, within a few percent RH.

The schedules were developed in the early 1950s.  At that time they were usually used with equipment that measured within 1/2 degree F.  Billions and maybe trillions of board feet were dried successfully with that equipment.  Obviously a safety factor was built into the schedule, recognizing the limits of the equipment.  Today, with better controls, we know what temperature we have to 1/10 F.  So, the old schedules can be accelerated a small bit with better controls without jeopardizing quality.  However, most operations do not appreciate a gain if the lumber is ready a few hours earlier.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #78 on: January 24, 2018, 10:43:57 AM »
I'm successful connecting all my sensors up and running basic tests.  Next up is some actual programming, not the monkey-see examples I've used so far.  The DS18B20 were giving me fits originally, even after replacing my resistor with a 4.7k one.  It turns out my little expansion board was causing the problem.  I ditched it and wired directly to the Pi and now all is well.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #79 on: January 25, 2018, 09:52:07 AM »
Good going, CT.

What other sensors did you get besides the DS18B20's?

I'm thinking there must be a humidity sensor out there that will stand up pretty well, but I haven't taken the time to look around yet.  If the wb thermo can be avoided, that's not a bad thing.  For now I'm installing both the 18B20's and DHT22's in the kiln.  I'll use the DHT22's for humidity and see how long they last.  In the mean time I can work on the wick and wb setup OR find some more robust humidity sensors.

I've been working on the installation, but haven't been able to spend a lot of time on it.  Finding ways to mount and shade the sensors takes a little time and creativity.  I still haven't come up with the box I'm going to use to house the electronics.  It's all progressing, but there other things on the agenda right now.

The software is pretty much done.  Right now it's set up to send 8 data fields up to Thingspeak and also store data locally in a csv file.  It will start a new file every Sunday morning at 5:00 a.m., so there will one week's data in each file.  The recording interval is set for 15 minutes, although that can be changed easily.  15 minute intervals seems about right - we'll see.  There's no problem making the sample interval shorter or longer.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #80 on: January 25, 2018, 01:24:43 PM »
I have a BME280 that I purchased from SparkFun.  It's on a little breakout board, not a package that seems like it would hold up well.  I got that because it provides barometric pressure as well as temp and humidity.

The 1-wire device is real easy to use and code for.  Configuring your system for it is a bit more of a hassle but the coding is nothing.  The BME280 on the other hand is easier to set up the system but the code is a mess.  I downloaded a python script to read it and am using that, but I haven't even attempted to understand it.  I'll delve into it later if the need arises.

Here's the code I started from to read the DS18B20:
Sorry but you are not allowed to view spoiler contents.

And here's the code I used for the reading the BME280.  Granted, I am reading three sensors here, so some additional complexity is expected.

Sorry but you are not allowed to view spoiler contents.

This is my one and only I2C device, but I think the complexity lies with the device and not the use of the I2C bus.  It's not a big deal, once the routine is written it's good to go.  But it has the feel of a kludge.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #81 on: January 25, 2018, 01:39:10 PM »
Somewhere in my internet travels I saw a humidity sensor chip that was packaged on a small board that was protected with a shrink-wrap cover.  A small hole in the shrink-wrap exposed the surface of the sensor itself.  I'm not able to find that now.  >:(

There's a good article on the different types of humidity sensors at https://www.sensorsmag.com/components/choosing-a-humidity-sensor-a-review-three-technologies
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #82 on: January 25, 2018, 11:47:37 PM »
Chugiak...the article you cited is 18 years old.  I am curious if any advances or changes in humidity measurement have been made since then, or is this still state-of-the-art-the-art information.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #83 on: January 26, 2018, 02:42:42 AM »
Thanks for pointing that out, I hadn't noticed the date.  I don't claim a lick of expertise in this area, but I doubt there's been any fundamental breakthroughs, at least that have gotten to the production stage.  Advancements have probably been in the realm of power draw, smaller and more sensitive sensors, improved operating temps, etc.  Evolutionary rather than revolutionary changes, I suspect.  But I am married, so that's proof right there that I am wrong on just about anything on a regular basis.   :laugh:
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #84 on: January 26, 2018, 06:37:40 AM »
We run by an adage an old woodworker taught me, which is now almost gospel:

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #85 on: January 26, 2018, 08:18:58 AM »
Good point, PA_Walnut.  Perfect is the enemy of done, also.  Since this is just an experimental thing, I've stopped worrying about some of the long-term issues and I'm just going with what I've got on hand.  If a few $3 sensors get consumed - oh well.  Some of those issues can be dealt with if and when they come up.  I'm using plain old cat5 cable and hard wiring the sensors that I have and we'll see how they fare.  It's not going to be difficult to deal with any failures that occur.  Besides, this thing might get retired after a year or so.  Collecting this data is just a matter of curiosity for me.  It's not necessary to do all this just to run the kiln and dry lumber.  We may even find some robust humidity sensors along the way.  There are many industrial processes being monitored and controlled with various sensors.  This has been figured out already somewhere.  I'm installing a couple temp sensors that can be turned into wet bulb sensors, but the mechanics of that can be figured out later, if at all.  The DHT22 sensors will work for now - maybe forever.  The BME280 that Chugiak is using is probably a better choice for measuring humidity.  We'll find out about all that.  It's easy enough to change some of this after the thing is up and running.  The only thing slowing me down right now is lack of time to sort out some of the installation issues, like finding the right size enclosure for the electronics at the right price.

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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #86 on: January 26, 2018, 08:46:44 AM »
instead of thinking of it as temporary I would think of it as a stepping stone to a fully automatic kiln that automatically adjusts the fans and vents to keep it at optimal drying conditions.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #87 on: January 27, 2018, 11:39:20 AM »
Sensors are all connected and reading accurately, as far as I can tell.  Here's a screen capture of my test program.  The Pi and sensors are still sitting on my desk and should report the same temperature, although there is a slight draft from the window in my office so some variation is expected.  Still, for any sort of accurate measurements each sensor should be individually calibrated.



A couple things I've figured out regarding the BME280:
  • The heart of the board is a Bosch BME280 multi-sensor chip that has an operating range of -40 to 85 C.
  • I can download and install the AdaFruit python library and that would clean up my code considerably.  It might also make it easier to access any additional features of the chip, if they exist.
  • The I2C controller is accessed at its internal address of 0x76 or 0x77.  That is controlled by a jumper on the underside of the breakout board.  That limits any system to two Bosch BME280 chips at a time.
Regarding the DS18B20 temp sensors:
  • I'm using encased waterproof versions of the Dallas Semiconductor DS18B20.
  • Each sensor has a unique serial number that is its address on the 1-Wire bus.
  • The sensors can be connected in parallel such that there is no prior limit to how many probes you connect.
  • Serial numbers are polled by the system, but if the probes are used for different functions you must know the serial number for each and make sure it's placed correctly.
  • I'm beginning to appreciate the elegance of the Dallas 1-Wire bus.  I'm sure I'll soon learn the shortcomings for it too, but for limited sensors and low bandwidth monitoring it seems well suited.

On wet bulb calculations of relative humidity:
  • There is no easy way to do this.  For a hot humid and corrosive environment, old school could end up being the most reliable.
  • There needs to be sufficient airflow over the wet bulb to ensure maximal evaporation.
  • In a kiln with fans running, that would probably be adequate.
  • If fans aren't running, or for desktop prototyping, a small computer case fan would suffice.
  • Calculating RH using a lookup table is cumbersome to code, but quite doable.



Edit to add:  I've been thinking about the potential for corrosion on the BME280 breakout board.  When I get to the stage that I am ready to install a remote weather station I will try coating the board in silicone.  The chip itself would need to be exposed to the environment, so a little blutack tape over that will protect it while I apply the silicone.  That's my thinking at least.  The housing for the chip will be exposed, allowing measurement of the humidity.  I don't think the rest of the components on the board will generate any heat to worry about.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #88 on: January 28, 2018, 08:54:06 PM »
I've set aside wet bulb measurement and the DS18B20 temperature sensors while I focus on local network reporting.  I started out doing my monitoring with a Python script and running that on a timer.  I installed sqlite3 and can easily dump records into a table.  My next challenge was to enable a local web service for monitoring from my desktop.

The Raspbian operating system comes with Node-Red installed, which is a visual programming tool well suited for remote data monitoring.  It makes use of Javascript and uses workflows to pass messages from one node to the next.  It's a different paradigm from what I'm used to so it's taking some time to learn new methods.

One of the problems I had was the difference in timestamps between Python, sqlite3, and Node-Red.  I bypassed that issue by having Node-Red do all the work.  I've dropped Python completely and am polling the BME280 with Node-Red, then passing the resulting data to a function that splits the temp, humidity, and pressure into three different messages.  The messages are then sent to dashboard nodes for display on the dashboard web page.

I've got the Pi sitting on my back deck sampling every 5 minutes.  Currently temps are around 10 F so the relative humidity reading is wacky.  I'm still working on understanding if it's just a wonky sensor or if the high relative humidity is because the air can hold so little water.  Here''s a snapshot from a few minutes ago...



Edit to add: Temp is in Celsius, relative humidity is percent, and pressure is in millibars.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #89 on: January 29, 2018, 05:11:08 PM »
Very cool, CT.  That's a nice looking dashboard.

I saw NodeRed on the programming tools menu, but I had no idea what it was.  I'm an embedded systems guy, so I tend to go in that direction.  I better investigate.  Besides, Jack Nicholson didn't fare well after ordering a Node Red in A Few Good Men.  I can't handle the truth!

Anyway, that looks good.  Can something like fan control be handled from NodeRed?  I don't have time to investigate right now.  I am neck deep in a bunch of things unrelated to any of this.   My logger is all done, except for the dashboard, and I'm working on installing and wiring it whenever I have a few minutes to put into it.  I must say that wiring and housing issues are not that interesting, but they are what's next for me.  By the way - I'm using hot-melt glue instead of silicon for weather-proofing little sensor pcbs.  I find it easier than silicon.  Just another means to the same end.

One of the data points I'm really interested in seeing when this thing gets installed is the difference between kiln rH and the rH figure that would be the result of raising outside air to the temp of the kiln.  That delta would show how much of the kiln rH is contributed by the evaporation of the moisture in the stack.  One of the challenges for the ambient air sensor is getting them far enough away from the kiln so the heat and escaping humidity doesn't spoil the reading.  It doesn't sound like a big problem, but in reality it complicates things a bit.  Like everything, the devil is in the detail.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #90 on: January 29, 2018, 08:37:40 PM »
I think Node Red was created for IoT and home automation, so it sure ought to be able to handle a little solar kiln management.  There are nodes for the GPIO on the Pi, so reading and writing pin status ought to be a snap.  Plus there is the module for the BME280 and probably every other major sensor.

For your ambient relative humidity, one option would be another Pi/Arduino and an accurate humidity sensor.  Or, would a reading from a nearby weather station be close enough for your needs?  Just a question that occurred to me, I have no clue how lumpy moisture distribution might be.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #91 on: January 29, 2018, 09:40:30 PM »
Seems like a perfect fit. I'm glad you brought it up. I wish I had known about it before I finished. I might still find a place to use it.

A second pi or arduino might be easier than running a wire. The sensor just needs to be away from the kiln so it's not getting heat and moisture readings affected by the kiln. Not far really. Doesn't need to be super accurate. Have you looked at some of the guidelines for placing outdoor sensors? Useful info. Noaa has guidelines. Siemens has a good white paper on all sorts of placement guidelines.

In the end, this only needs to be as accurate as the user wants it to be. I've found that temperature varies a lot around my place.  If I wanted to skew my temperature readings for a desired outcome it would be pretty easy.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #92 on: January 29, 2018, 09:48:54 PM »
An aspirated housing seems to be the easiest way to deal with outdoor sensors. That's what the inexpensive weather stations use. Lots of examples out there mzde with pvc pipe and old cpu fans.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #93 on: February 03, 2018, 07:38:23 PM »
Finally found what looks like a good enclosure without breaking the bank.

https://www.amazon.com/Orbit-57095-Weather-Resistant-Outdoor-Mounted-Controller/dp/B000VYGMF2

It has a panel inside as well as a GFCI outlet.  Will have to get one and see how it checks out.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #94 on: February 05, 2018, 09:12:19 AM »
I'd call that a perfect solution CT.  Good find.  That never turned up in my searches.  FWIW, Home Depot carries that same box for 32$ and it's in stock at the closest HD.  https://www.homedepot.com/p/Orbit-Outdoor-Timer-Box-57095/100158884  I'm going to pick one up today.  I had a box I was going to use, but it wasn't well suited to the task.  This looks perfect.

I've been completely tied up for the last week or so and unable to do anything on the installation.  This week I'll have a little time here and there to work on it and the box you found will get me over the hump.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #95 on: February 05, 2018, 12:38:31 PM »
Credit weathernick at WxForum.net for that enclosure.  He's got a very detailed Pi build for his weather station.  If you haven't read that thread yet, it may have some helpful info for your kiln monitoring.

I'm jealous that you can have instant gratification at Home Depot.  There are none of those stocked in Alaska.  I've been stuck at home the last few weekends, as temperatures at the property are uncomfortably cold.  Currently -36 F out there so I'm staying home instead and working on chores and my Pi project.

I'm not sure if it's a good fit, but have you looked at WeeWX?  It looks to be a decent way of displaying your sensor data.  I'm going to dig into it when I get a chance, as it may do most of the things I need for my weather station.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #96 on: February 05, 2018, 02:51:20 PM »
I was very surprised that it turned up at HD and in stock no less.  It's probably because 50% (or more) of the homes around here have sprinkler systems.  I guess our weather is just a wee bit different than yours  ;).  I just got home with the newly acquired box.  It's going to work just fine.  Hopefully I can start fitting it up and get this thing installed.  I'm still pretty tied up on other things, but I have some cracks here and there.  The kiln is sitting empty until I get this thing installed, so I'd like to put it back in service.  The days are getting longer here now even though February is usually our worst weather.  I think maybe we got some of our  bad weather out of the way early, but the ground hog says there's still plenty of time for ugly weather.

I'll take a look at those sites.  Sounds like some interesting and useful stuff.

Stay warm.  -36 is not part of my DNA, and I don't expect that to change anytime soon.
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Re: Kiln temp and humidity logger using the Raspberry Pi platform
« Reply #97 on: February 12, 2018, 07:38:38 PM »
Seems like nothing's been going on with this thread lately. That's because I've been tied with a lot of mundane other things, but it looks like I'll be able to get the stuff installed this week hopefully.  There were lots of little details to work out with sensor housings and sunshades and wiring but most of that has been worked out.  Stay tuned.
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