PID

[rodmkr]

How many use one?
How accurate is it?
After 3 years finally got a chance to set mine up.
It is one I purchased on the other site from OB2 ( I think that was his handle).
Set it for 750 , it overshot and then settled down to approximately 775.
Lowered temp setting to 700 and it ran at approx 685 to 725.
Is this normal?
If not what am I doing wrong?

rodmkr

 

[S Mac]

I can only answer your first question, don't use one. Would probably be ok, but I have managed for some time without one.

 

[popper]

It has to 'learn' your system. Different amount of alloy heat differently, there is a setting to reduce the temp window - after it is running for ~1/2 hr. There is also an offset setting to calibrate POT temp to indicated temp. Also have to set K type thermocouple if that is what you are using. Normally, heat it up 3 times for an hr before changing settings so it can learn. Normally it will learn to be very accurate but will overshoot at first. Set your POT controls to max!

 

[Brad]

I have a couple and wouldn’t be without them.
I do think they can take some time to “learn”. Someone with more electronics knowledge than me can explain that.
I use one on my PC baking oven and once at temp it just flatlines at that temp. The casting pot PID is interesting because it shows what happens when a cool ladle or ingots are added. Being able to see the temp dip is a learning experience.

 

[rodmkr]

Thanks all,
At least I know I didn't screw it up.
That was my worry.
Will keep using it and hope for the best.

rodmkr

 

[Brad]

I would set and let it sit for maybe 30 min with no casting, etc. let it really settle in.

 

[RicinYakima]

Mine was built by my friend "Uncle Russ", Master Electrician. All PID components are not equal, so they take some getting used to depending upon the build. This one after an hour will run +/- 2 degrees to setting with at least 1/2 full of alloy and it is accurate because we did the water calibration. My new RCBS will only keep +/- 10 degrees but that may because of the cooling fan built into it.

Follow "popper"'s instructions and it will work out for you.

 

[JWFilips]

Love it for my PC baking oven! However load oven too much and you have to reset the pid Settings
Just found that out

 

[Mike W1]

I get the impression that you may not have auto tuned (AT) your unit. The way I was instructed was to set the temperature you want and then let it start heating your pot. When you get to within about 20-30° of your desired temp engage the AT feature and let it do it's thing until it's donel. You'll know as the AT will then go out.

I don't know this for a fact but I don't think the PID controllers we use keep learning. The way they learn is thru the use of the AT feature and you aren't not going to hurt things by doing a AT more than once.

Learn how to go thru the list of parameters and record them. If you've been playing with the unit it is possible to change one and not realize it. Compare what's there with the list in the PID instructions. Usually the factory settings don't need to be changed to control a lead pot and most come set for a K type TC.

When you get things going good you may find if you change the SET temperature you may have to do AT again. I haven't found it necessary to do so with smaller changes though.

ATing changes the values of P, I and D and these are the figures you'll want to record and have available if you want to go back to some other project. It'll eliminate having to AT all over again with a similar pot.

I have 4 units and they stay roughly ± 2° of SET temperature.

PM me if I can be of any help.