Kiln temp and humidity logger using the Raspberry Pi platform

[JoshNZ]

I upgraded the little relay board to SSRs today. Noticed the third or fourth load maybe I was starting to get relays sticking particularly on the heater.

Opto22 have a series of SSR relays, on the bench they only drew 2.1mA from the pin at 3.3v which is pretty amazing.

The pi and software have been great, hasn't missed a beat yet otherwise.





I cracked one of the little blue relays open to look at the contacts, they're about the size of a ballpoint pen end  ;D don't know where they got their 10A rating. Better not to use them in kiln projects.



 

 

[Crusarius]

thats 10 amps in chinese metric

I have been wondering the same thing about alot of that stuff. I know for a fact some of those 30 amp switches I would not trust with 10!

[JoshNZ]

I've been pondering another couple of questions about my kiln and thought this would be the best thread to ask them in..

All still going great, the pi controller is a fortress. Will be another kiln or two on the way at some point.

I wondered - should I be including a defrost cycle in my software? Practically speaking is it OK to run the compressor for 24h straight, or does it want to switch off for 6 minutes every hour to thaw the coils? Right now it is running continuously and still seems to bucket water out when I've got a green load in there but I'm wondering if this is optimal.

Also, I would like to encorporate an "EMC at given settings" on the interface page so I don't have to refer back to tables. I see there are calculators online which take a temp and RH, but I thought it must surely vary from species to species? Is there a one size fits all formula?

I've been creating a list of error conditions for a watchdog timer type piece of code to check, simple things like temp gradient too steep upwards (fire or failure), or downwards (stranger opened door and stealing wood!), and a power cut check - this one has caught me out a couple of times as the pins are defaulted to low on power up.