DIY Heat Treat Oven Build

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Sorry! I was doing my original testing at 440°F. I have my I=9999 and D=0

Testing now at 1600°F, at least three fluctuation cycles each.
P=150 up 10°, down 25°
P=70 up 12°, down 20°
P=35 up 12°, down 23°
P=300 up 15°, down 20°
 
P=700 up 7°, down 23°

I've had control period at 1 for all this!

This huge P range with very little change is making me wonder if something is up with the PID itself... I guess 7 up is half the previous value though! I'm gonna try at P=1400 next.
 
P=1400 up 12°, down 18°
P=2800 up 12, down 17
P=5600 up 15, down 15

I think that last one is about the best I'm gonna get, unless you have any better ideas lol
 
is the p=5600 centered on the setpoint?

(sorry ... gotta quit for tonight ... time to eat dinner ... we always eat late :-(
 
Are any of you guys worried about your DIY oven burning the shop down? I can't imagine home owner's insurance wanting to pay for that.

I'd like to build an oven but that scares me off.
 
Cushing H. said:
is the p=5600 centered on the setpoint?

(sorry ... gotta quit for tonight ... time to eat dinner ... we always eat late :-(
Click to expand...

Yes! At 1600°F set value and P=5600, the temperature fluctuated from 1585°F to 1615°F

No worries sir, you have been incredibly helpful already!
 
N.W. Gean said:
Are any of you guys worried about your DIY oven burning the shop down? I can't imagine home owner's insurance wanting to pay for that.

I'd like to build an oven but that scares me off.
Click to expand...

Nah, as long as you're being safe with the electronics, have the oven properly insulated, and you aren't leaving flammable or combustible materials laying around then you should be fine.

Edit: you could always do your testing outside and keep a fire extinguisher handy.
 
Cushing H. said:
Just for yucks ... what if you set p to 9999 ?
Click to expand...

I didn't go that far but I tried changing all the PID values, I tried switching from manual inhibit to automatic, and I tried adjusting hysteresis. At 1200°F watching at least 3 fluctuation cycles with each change in settings, there was less than 2°F variation in the temperature fluctuation. In other words, all of those settings do absolutely nothing. Either my PID is faulty, or the entire line is, oof.

Edit: I counted approximately 22 individual changes. At least 3 cycles each for a bare minimum of 66 temperature fluctuations that followed the exact same pattern: down 11°F, up 27°F
 
Cushing H. said:
Just for yucks ... what if you set p to 9999 ?
Click to expand...

The only thing the P value seems to change is how often the elements flicker on and off as the temperature drops below set value. Once it's set higher than 10 or so, the percent power use just immediately maxes out once the temp drops.
 
Tarkus said:
The only thing the P value seems to change is how often the elements flicker on and off as the temperature drops below set value. Once it's set higher than 10 or so, the percent power use just immediately maxes out once the temp drops.
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The manual drives me crazy - it is just not clear on P.

do you have your SSR wired to the #6 and 8 terminals on the inkbird ... and is the polarity correct?
 
Wait ... you mentioned you tried setting hysteresis? There is no such thing for PID control (or should not be).

do you have the control mode (op/ctrl) set to PID??? (Or is it set to on/off)? Sorry if this seems a stupid question ... just trying to cover the bases...
 
Another wild ass guess: if you have the control mode set to PID, and you change the hysteresis parameter, AND you see a marked change in behavior ... then the controller is just plain doing something weird with its control algorithm
 
I'm in a 220V circuit so I'm using a dual SSR setup with a deadman door switch. The SSRs are wired together in series with the switch and unless something is labelled wrong, the polarity is correct.

You are correct, the hysteresis was in the alarm settings! Someone mentioned it might do something so I tried it, but nothing lol

I have it in PID mode. I tried with on/off and the temp just kept rising. I also tried with the auto tune function and that just made the fluctuations worse.

Edit: no such thing as stupid questions! You need all the info you can get and I appreciate it!
 
Another wild ass guess:
If you minimize both I and D (I=9999, D=0), and then you try P set to both 1 and to 9999, AND you do not see some REALLY big change in behavior (again, control mode must be PID) then something Is really, REALLY weird. Controller might be bad (not likely but possible).
 
So with the dual SSR’s, you have two separate outputs (from the ssrs) driving two independent heating coils?

I honestly don’t know if it would make a difference ... but I would think it more appropriate to wire the connection between the PID output and the ssrs so that the ssrs are in parallel to each other (but keep the door switch in series to the pair of ssrs...
 
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Stacy E. Apelt - Bladesmith said:
How long are you letting the oven run at the settings given?
+/- 15° at 5 minutes may be +/- 5° at 30 minutes.
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Stacy .. that s very true. The angle I am chasing though is his comment that kind of whatever he does, the elements come on full bore when he drops below setpoint. With the effect of I and D minimized, he *should* be able to set P so that he has a really, really wide proportional band ..
And when he drops below setpoint by a few degrees, the elements are just barely nudged on...

i *think* the P parameter for the inkbird is a raw temperature band (units of F) ... But the manual is totally vague on that point...
 
Max I and min D, I went from P=5 to P=5600 and saw no noteable temperature change after a few minutes of watching.

About 5 minutes is how long I monitor but I'd think with such big settings changes, it would do SOMETHING different.

Only one element. I used Dan Comeau's wiring diagram for a 240V circuit. I don't know what a PIC is or why they should be in parallel, sorry...

Edit: only one output from the two SSRs to power the single element!
 
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