Recommendation? Help with Inkbird PID settings?

IVKnives

IVKnives

Joined
Aug 4, 2015
Messages
28
Hey y'all,
I just finished building my DIY heat treat oven. Doing the math, I figured its right at 1000 watts 120v with an interior chamber size of 4"x4"x15.5". I left it to run on factory settings to try to achieve 1475 degrees for an hour but when I came back it was sitting just over 1000 degrees but still climbing. Since my input power should be adequate, I'm assuming this has something to do with the PID settings. Do any of you guys have any experience setting up Inkbird PIDs for smaller furnaces? What kind of settings should I have in there as far as integral times and derivative times? I've tried to google it but so far I've found nothing.
Thanks for any help
 
There should be an "out" LED on the controller, which is lit when the output is energized. Watch it for a while and see if it stays lit continuously. If it does, the elements are being fed continuously and the problem is not with the PID settings. It is quite likely that the thermal mass of your oven is high for the power input and it will take a long time to reach temperature.

If the output is cycling, note the temperature and try to time how much of the cycle the LED is on for. Adjust the setpoint to maximum and see if the "on" light LED lights for a greater proportion of the cycle. If it does, check your PID settings. Make sure you have the Integral set to a value of at least one.

Let
 
make sure the thermo couple is connected properly. Some ebay items have the leads as different colours or are reversed. Also, if the TC is sleeved, make sure it's set all the way down in the sleeve and not pulled up. The actual TC just slides in the sleeve. My inkbird seemed to run pretty well at factory.


Also, make sure you close the door ;)

I just remembered that the inkbirds default in degrees C. I changed out my PID once and burned out my elements when it ramped up yo up to 1450 degrees C. Man that was hot.
 
The PID control is simply a switch, it allows power to flow through the heating element upon a call for heat (initiated by detecting a difference between the setpoint and current temperate). 1000 watts is very low, my original element was somewhere around this value and it never got up to temperature (with a small chamber size). I experimented with making different length coils to see which resistance value (and therefore, amperage, Ohm’s law) would produce an acceptable result. My second coil had too little resistance and quickly melted. My third coil ended up providing me with an amperage of 17 at 220v, meaning that my wattage is around 3740. This sounds ridiculous, but has been absolutely perfect. The coil has had no issues and my oven gets up to 1500F from room temp in ~10 minutes. Hope this helps
 
Set it to auto tune.

Edit: I have the Inkbird. This is by far the simplest way to do it. I think you toggle to "CTRL" then toggle through the options and select "AT." Easy peasy.
 
Do you have to set to auto tune each time?
I try that and it seems to keep reverting back.
tkroenlein said:
Set it to auto tune.

Edit: I have the Inkbird. This is by far the simplest way to do it. I think you toggle to "CTRL" then toggle through the options and select "AT." Easy peasy.
Click to expand...
 
Update: I've gotten the oven working reasonably. The heating element was too long so I decreased it to get the power to 1500 watts. Now I'm having an issue getting the PID to remain stable. Its getting to temperature and shutting off immediately, going like 2 degrees over and then dropping 10-15 degrees below. I've tried autotuning it 3 times now and it hasn't worked yet. Could anyone share their successful settings or spare any tips?
 
I can't really help a lot with the info given, but check that the hysteresis is not too tight ( try +/- 5 degrees). Also check the heating rate.

Auto-tune should learn the ON/OFF cycle times needed to hold a reasonably close temperature., but if it resets to default mode and disables auto-tune each time you shut off the power as mentioned, it probably forgets all it learned.

Finally, don't sweat the variable cycle times shown. That is the air temperature and not the blade temperature. The blade reacts much slower, and the average is usually very close to the set target.
 
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