PID help needed

rasret01

rasret01

Joined
Mar 31, 2009
Messages
153
I just converted my sugar creek oven to digital control - syl 2352-p pid and ssr's from Auber wired according to the schematic recommended here. For now,I'm just trying to get the oven to go to 1465F and stay there 'til turn it off. I tried programming according to the pid manual(s), but all I get is a very slow (2hr) rise to a seemingly infinite temp (Waaaay to hot for O1) but with only 825 indicated on the pid. I'd be very grateful for any insights...

Dick
 
Make sure the thermocouple wires are not just reversed (which would show an eventual negative number) but that all the connections remain consistant all the way through. Also, make sure it is a K type thermocouple. It will apply max power to try and get to your target but if your thermocouple is the the wrong one, it will rise infinitely. Also, review the programming thread in the PID stickies from Jim Vail to make sure you have your steps entered correctly. My guess is that you either got the wrong thermocouple or the wiring is incorrect.
 
I have the parts to convert mine but haven't done so yet but from what I have gathered you need to do 4-6 dry runs up to approx. 1500 degrees because the PID has to "learn" when and how often to turn the coils on and off to maintain the desired temp.. Once this learning period is complete it should hold the temp. within 1-2 degrees of your target. Bear in mind that this is with the proper parts installed correctly.
 
My thermo couple is right - type K - and the wiring seems correct. I refined the program steps for another try and although it seems to be working, the pid readout is still at least 100 degrees lower that the actual temp in the oven)reads 225F when an oven thermometer reads 325+. I have used the auto tune feature to educate the pid. I'm beginning to think my new thermocouple is bad. It reads the 65 degree ambient temp at 20 when I turn it on. My old analogue controller started doing the same thing, which is what prompted the switch to new TC and digital controller.

Thanks for your thoughts.

DIck
 
Something is wrong ,but it is hard to tell what. Check the wiring, polarity, etc.
ib2b4u will hopefully chime in, as he is quite familiar with these conversions.

The first thing that jumps out is that it reads 825..... did you set the PID to read F or is it still set to C...825C is 1515F?
My next thought was that it was still running on analog ( with the PID only turning on power to the analog circuit). Did you completely remove the old analog switch and power cord, and wire directly to the coils? If you applied the power to the oven by merely wiring the SSR to a socket and plugging in the oven, you will have to set the analog dial to MAX to get normal running.

BTW, I assume the oven ran fine before the conversion?
 
Something is wrong ,but it is hard to tell what. Check the wiring, polarity, etc.
ib2b4u will hopefully chime in, as he is quite familiar with these conversions.

The first thing that jumps out is that it reads 825..... did you set the PID to read F or is it still set to C...825C is 1515F?
My next thought was that it was still running on analog ( with the PID only turning on power to the analog circuit). Did you completely remove the old analog switch and power cord, and wire directly to the coils? If you applied the power to the oven by merely wiring the SSR to a socket and plugging in the oven, you will have to set the analog dial to MAX to get normal running.

BTW, I assume the oven ran fine before the conversion?
 
Thanks Stacy

I completely removed the old controller - started new. Polarity ok, display set to f. The oven ran fine before except for the temp display reading low as it does now. The only thing left of the old setup is the element, and I would assume that an element either works or doesn't. This one heats up fine. I'm hoping for ib2bfu too.

Dick
 
I know you said you'd checked, but I'd check the thermocouple wiring again, as it's the most common cause of this sort of problem that I see in my day job. Are you using the correct type K extension (or compensating) cable and are you using the positive core for the positive leg and the negative core for the negative leg?

Each junction in the circuit that involves dissimilar metals will generate a voltage. There "should" be no junction at the connector block on the back of the oven, because you are connecting the same core compositions in the cable and the thermocouple. However, if you use the wrong cores, there will be two unexpected junctions in the terminal block and they will be of opposite polarity to the "real" junction.

I've had a long week and a couple of drinks, so my math may be off, but as an example, lets assume you have the oven at 1500 degF, the connector block at 250 degF and the controller at 70 degF, with the cores in the cable transposed.

The "real" junction will give a reading of +1430 degF relative to the controller (1500 - 70), and each of the unintended junctions at the connector blockwill give a reading of -180 degF relative to the controller (the controller has an internal Cold Junction Compensator, which tells the controller what its actual temperature is. What it "sees" from the thermocouple is a voltage reading that corresponds to how much hotter or cooler the hot junction is than the cold junction/controller). The controller would show;

70 + 1430 - (2 * -180) = 1140 degF at an actual 1500 degF oven temperature.

(I'm assuming the two unintended junctions on the controller itself will be at the CJC sensor temperature, so will not affect things)
 
Timgunn is correct in that the wires running to the thermocouple need to be right not just to postive to positive on PID to Positive on Thermocouple, but ALSO the right wire of the 2 has to go to the right + and the right one to -. The 2 wires are not the same type wire and must match the right thermocouple leg. Did the Thermocouple somehow get turned around in its mounting block that has the + or - on it? Is your PID set for a type K thermocouple? That is the USUAL default setting, but, maybe it got changed. There is also an offset that can be programmed into the PID that will offset the PIDs read temp to the actual temp.

Trying turning the wires over at BOTH the thermocouple and the PID and see if it changes readings.

Hopefully that does it.

In order to check that the PID is set to type K you need to get to the Sn mode and check for a 0 setting for type K

The offset is with the Pd mode

The directions for accessing those are on page 3 of the first part of the instructions which you can download here. I advise downloading and printing them and keeping a set near your oven. Figuring them out a first can be confusing. Programing the set points and ramp times takes a bit to get used to and I made cheat sheet I keep by my oven. I think it might be in the stickies. I am away from home working a job for the next month or so, and will shortly be at work 13+ hours a day 7 days a week. Then maybe a short break before another month of the same then the summer OFF and August I go to social Security and freedom. LOL I will still do a job once and while, just pick and chose more.
 
ib2v4u said:
Timgunn is correct in that the wires running to the thermocouple need to be right not just to postive to positive on PID to Positive on Thermocouple, but ALSO the right wire of the 2 has to go to the right + and the right one to -. The 2 wires are not the same type wire and must match the right thermocouple leg. Did the Thermocouple somehow get turned around in its mounting block that has the + or - on it? Is your PID set for a type K thermocouple? That is the USUAL default setting, but, maybe it got changed. There is also an offset that can be programmed into the PID that will offset the PIDs read temp to the actual temp.

Trying turning the wires over at BOTH the thermocouple and the PID and see if it changes readings.

Hopefully that does it.

In order to check that the PID is set to type K you need to get to the Sn mode and check for a 0 setting for type K

The offset is with the Pd mode

The directions for accessing those are on page 3 of the first part of the instructions which you can download here. I advise downloading and printing them and keeping a set near your oven. Figuring them out a first can be confusing. Programing the set points and ramp times takes a bit to get used to and I made cheat sheet I keep by my oven. I think it might be in the stickies. I am away from home working a job for the next month or so, and will shortly be at work 13+ hours a day 7 days a week. Then maybe a short break before another month of the same then the summer OFF and August I go to social Security and freedom. LOL I will still do a job once and while, just pick and chose more.
Click to expand...

Thats what I was saying......thanks for spelling it out:D
 
Thanks guys. I'm going to check with Auber support on Monday. I've got the positive side of the pid to the positive side of the block and the yellow - positive - wire to the positive pid connector. I programed a zero degree ramp to take the oven from ambient to 1465 and stay there. When I turn it on, the oven heats nicely, but the steel goes non-magnetic at about 725 f as indicated on the pid. All the programmable parameters are set at factory default - k type TC, Fahrenheit display, etc. I'm at a complete loss and thinking seriously about taking up knitting for a hobby.

Dick
 
If you have a multimeter, it's worth measuring the milliVolt reading that you are getting across the input terminals on the controller at a couple of different temperatures, ideally as far apart as you can easily get them.

There's a table at http://www.omega.co.uk/temperature/pdf/Type_K_Thermocouple_Reference_Table.pdf that will give the temperatures corresponding to millivolt readings from a Type K thermocouple. Note that they are in degC and you'll need to covert to degF.

The following should give a similar table in degF

http://www.google.co.uk/url?sa=t&rc...wIDgCw&usg=AFQjCNHAP62AKiHYGzgMB-_pzmcqXdSsXA

It's worth doing before phoning tech support if you can, because it will help to locate the problem; If the millivolt readings correspond to the display, the problem is outside the controller. If the millivolt readings do not correspond to the display, the problem is within the controller.
 
Good luck and please let us know what you find out. I have have 4 of their PIDs and happy with all.
 
HA! Got it. As usual, the problem was the idiot behind the wheel, and it took my son to notice the parameter mis-setting that was causing the Celsius readout (good catch, Stacy). Thank you one and all for your help. I'm back in business and relieved that I don't have to take up knitting after all.

Dick
 
Glad you got it. Just because the default settings are supposed to be something doesn't mean they are.

You are really going to like the possibilities that the ramp soak opens up. Remember that for soak time you need to program in 2 identical temps back to back and set the time.

I like to set my oven to go to a temp about 50f below my final target and soak there for a bit, then go up to my target temp in about 10 minutes. Gives the oven a chance to even out and then go to the final. Lot less chance of any kind of overshoot.

You can now correctly anneal high alloy steels too.
 
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