Anyone good at math ?

[Kbeitz]

I'm trying to build a simple set for my mill. I got all my parts and got
most of it put together. I got one problem that I could use some help with.
The rotary wheel that will follow my carriage is 12" in circumference or
around 3.83" in diameter. The wheel is mounted on my rotary pulse
generator. One turn of the wheel give me 600 pulses from my  pulse
generator. So my PLC gives me a reading of 600 for every foot of
travel. So my question is. What size wheel would I need to give me
a reading of 1000 pulses in one foot of travel ? All I know is that it needs
to be smaller by I'm guessing around 1/3.
I need 400 more pulses per 12" of travel.
Would that be as simple as 40 percent smaller ?
1.233" smaller ? That would mean that I need a wheel 1.850" in diameter.

Right ? Wrong ?

[Dan_Shade]

Do you get pulses from the shaft turning, or from teeth on a wheel passing a sensor?

[Dan_Shade]

I  calculated it to be a circumference of 7.2", which is a diameter of 2.292".

You need 1000 pulses per 12" of travel if the wheel is in contact with the surface?  I calculated 1 2/3 rotations of a 7.2" circumference wheel to travel 12"....

[TimRB]

Nuts--not quick enough...

Anyway, I get the same thing as Dan.

Tim

[Kbeitz]

Do you get pulses from the shaft turning, or from teeth on a wheel passing a sensor?

Pulses come from a rotary pulse generator. It contains an LED light source
and a photo sensor that scans a shaft mounted slotted disc.

[Kbeitz]

I  calculated it to be a circumference of 7.2", which is a diameter of 2.292".

You need 1000 pulses per 12" of travel if the wheel is in contact with the surface?  I calculated 1 2/3 rotations of a 7.2" circumference wheel to travel 12"....

Thanks... A lot...

[JohnW]

I like arithmetic a lot, but I don't know what you're talking about.  With this type of problem, with pulleys and revolutions, the change is always directly proportionate to the circumference or the diameter, either one.

One thing though, if you change the size of this wheel, is it going to be doing less work, and start turning faster?

[Den-Den]

PLCs are really good at math, just adjust tweak the software to compensate for the pulses that you are getting, no need to change hardware just to make the math easier.

[Kbeitz]

PLCs are really good at math, just adjust tweak the software to compensate for the pulses that you are getting, no need to change hardware just to make the math easier.

It's so much easier when your working with 1000ths of an inch
Instead of 600ths of an inch.

[Kbeitz]

I like arithmetic a lot, but I don't know what you're talking about.  With this type of problem, with pulleys and revolutions, the change is always directly proportionate to the circumference or the diameter, either one.

One thing though, if you change the size of this wheel, is it going to be doing less work, and start turning faster?

No real work. The wheel is just rolling along measuring the distance traveled.
Like this.



  

[coxy]

 ??? ??? could you all explain this in English  ;D :laugh: never mind this way beyond what my brain will handle  :D  good luck

[Kbeitz]

??? ??? could you all explain this in English  ;D :laugh: never mind this way beyond what my brain will handle  :D  good luck

Does this help ?



 

[Dan_Shade]

Having it roll on a surface may allow slipping of the wheel, maybe a rack and pinion would work. (I would put guards around any gear mechanisms.

MSC carries an assortment of rack and pinion gears.

My setworks has an encoder on the chain that is utilized to raise and lower the head.   The newer woodmizer setworks use a transducer rod.

[sandsawmill14]

kbeitz  i think you will be good with the wheel you have as it is 50 pulse per inch if it is 600 pulses per rev when you are scaling the plc just multiply x 20 to get to 1000s if you go to 1000 pulses per foot that will give you 83.3 pulses per inch and i would think that would be harder to work with but good luck whatever you decide

if you set your scaling as .020 per pulse should get you close that will make you gain .005 per cut so your dog board would be about 1/8 thicker on a 24" cant if you are cutting 4/4 lumber with no cant   i am doing this math in my head so double check all those numbers but it should be pretty close ;)

[sandsawmill14]

we have used those type wheels up to 600ft per min  on radiator tube mills with no problems but they were running horizontal so he will have to use some kind of spring loaded mount or something to hold constant steady pressure for it to work kbeitz  if it does slip you will pull you hair out trying to catch it because it wont slip 1/2 a round it will slip 2 pulses every once in a while and you cant tell if its in the scaling or in the hardware :D :D :D :

[pineywoods]

Them optical encoders are quite common in the computer world. Anywhere there is mechanical motion, tape decks, printers, large disk drives,etc. The multiple patterns and outputs are there so the software can figure out which way the disk is rotating. Useful on cnc applications also..

[Kbeitz]

kbeitz  i think you will be good with the wheel you have as it is 50 pulse per inch if it is 600 pulses per rev when you are scaling the plc just multiply x 20 to get to 1000s if you go to 1000 pulses per foot that will give you 83.3 pulses per inch and i would think that would be harder to work with but good luck whatever you decide

if you set your scaling as .020 per pulse should get you close that will make you gain .005 per cut so your dog board would be about 1/8 thicker on a 24" cant if you are cutting 4/4 lumber with no cant   i am doing this math in my head so double check all those numbers but it should be pretty close ;)

Thanks... I'll try that.

[coxy]

  smiley_alcoholic_01 smiley_dizzy smiley_dizzy smiley_dizzy smiley_dizzy :D :D

[DelawhereJoe]

....will the bearings in the unit handle the extra speed of the smaller wheel and are the smaller wheels going to clear the body of the sensor ?

[Kbeitz]

....will the bearings in the unit handle the extra speed of the smaller wheel and are the smaller wheels going to clear the body of the sensor ?

This is for the up and down of the carriage and that move real slow.
I could use a smaller wheels because I will be only using one wheel.
But i think I will do as Sandsawmill14 suggested and set my scaling
as .020 per pulse so i wont need to change the size of the wheel.

I want to thank everyone for your help. Love this forum .

[sandsawmill14]

good luck with it 

[kensfarm]

The simple setworks uses a wire.. the sensor is stationary..  kinda like a tape measure that self retracts. Then you don't have to worry about the wheel slipping.  Might be able to use a tape measure w/ holes in it for your led/sensor pick up

[sandsawmill14]

yes the encoder will be stationary but the wheel will roll as the head moves up and down   sorta like when you get you truck stuck ;) the wheels are turning but nothing is moving

[Kbeitz]

kbeitz  i think you will be good with the wheel you have as it is 50 pulse per inch if it is 600 pulses per rev when you are scaling the plc just multiply x 20 to get to 1000s if you go to 1000 pulses per foot that will give you 83.3 pulses per inch and i would think that would be harder to work with but good luck whatever you decide

if you set your scaling as .020 per pulse should get you close that will make you gain .005 per cut so your dog board would be about 1/8 thicker on a 24" cant if you are cutting 4/4 lumber with no cant   i am doing this math in my head so double check all those numbers but it should be pretty close ;)

I had some problems with my eyes and my project got put on hold for
a few days. Well today I got to work on it. I worked on it a few hours
trying to find out how to program it. I was following the book but I
wasn't getting anywhere. Then I found out my 12 volt power supply was
not strong enough. Low current. So after I got that fix the programming
went well. I set the scaling as .020 and it wasn't coming out right.
I ended up with .180 to get it right dead on... No idea why.
I wish my encoder was lower resolution. If I turn the wheel to fast the
PLC cant keep up. I don't think I will have that problem when it's on
the mill because it will be turning slow.

[sandsawmill14]

well i said my math should be close ;D :D :D :D
glad you got it worked out scan time on the processor may be to slow to keep up when spinning the wheel but unless your head is really fast i dont think it will be a problem once on the mill

good luck and keep us posted

[VictorH]

yes the encoder will be stationary but the wheel will roll as the head moves up and down   sorta like when you get you truck stuck ;) the wheels are turning but nothing is moving

I believe what you describe is called a "string pot"

[sandsawmill14]

i think  kensfarm is talking about a string pot but what I was talking about is simply an encoder with a wheel on it

[Brad_bb]

I get the same as Dan too.  Guess I'm really late here.  Didn't read all the replies before doing the math.
I tend to look at the problem as ratios.
600 pulses is to 1 revolution as 1000 pulses is to x , which is written as
600/1=1000/x
solving for x
x=1000/600 = 1.667

Now you know how many revolutions equals 1000  pulses

So now if you want to know the size of the wheel that will give you 12 inches in 1.667 revolutions, you write it as
1.667(2*Pi*r)= 12 inches
Note: 2*Pi*r is the circumference of the wheel, where r is the radius and Pi is 3.1415
Solving this equation for r
r=12/(1.667*2*3.1415) = 1.146 inches
multiplying by 2,  the diameter of the wheel equals 2.291 inches, and a circumference of 7.200 inches.

[ozarkgem]

I will use a vertical stationary chain and the encoder will move up and down with the head. A sprocket on the encoder will be used to turn the encoder. No chance of wheel slippage.  Are you spring loading the wheel so it will stay in constant contact?

[Kbeitz]

I will use a vertical stationary chain and the encoder will move up and down with the head. A sprocket on the encoder will be used to turn the encoder. No chance of wheel slippage.  Are you spring loading the wheel so it will stay in constant contact?

Spring loaded mounted at the top away from everything.

[Kbeitz]

I took some time thinking and playing with the scaling.
I think I'm going to set it up for reading 1/4" This would
make reading it so much easier. The scaling for that came
to .800. Bow if I want 1" I just run it to 4. 2" = 8 and so on.