PID Thermo controller

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Sebas83
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PID Thermo controller

Postby Sebas83 » Tue Mar 01, 2011 10:02 pm

Hey everyone. Have some issues with my PID:

It's a REX C100 which is frustratingly close to the CD101 except its controls are not the same. And by C100, I mean the "C100." It was cheap and on eBay from China. Just hoping someone has worked this out before me.

1) I can't get into the lower layers of the software... before you go to google to get your answers, I've been there. The supposed move doesn't work on this unit, and this is my second one after shipping the other back. Anyone out there know this one? Bueller?

2) When the K-Type thermocouple is wired into the terminals, I get an "over" PV reading. When it isn't tied in, I get a reading of 750-850. If I repeatedly tap one contact to the second terminal (other is in) I can "manually" decrease the value. Clearly this is not a solution, just an observation. Really, it looks like a short-circuit. But, this is a BRAND NEW unit and thermocouple. Plus, this happened with the first unit as well.

Any takers? Getting desperate.

-S

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mightyohm
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Re: PID Thermo controller

Postby mightyohm » Tue Mar 01, 2011 11:03 pm

When I power up my CD101 with no thermocouple connected, I see "oooo", which according to the manual means "overscale".

mnphysicist
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Re: PID Thermo controller

Postby mnphysicist » Wed Mar 02, 2011 7:30 pm

I'm not familiar with this make and model, but have designed tons of similar devices.

Most units have a thermocouple break protection circuit, either a constant DC bias, or a pulse. The idea being if the thermocouple opens up, the controller will go into an overrange mode, and shut down its outputs. If a thermocouple has drastically higher impedance due to a bad spot weld or possibly a bad swedging operation, all sorts of bizarre behavior can occur, more so it its using pulse style of open circuit detection.

The indication of "ooo" would indicate typically indicate a bad thermocouple. However, being you can drive the output indication lower by taping on the input connector suggests something else may be occurring... that can be tricky, especially if break detection is accomplished via a pulsed signal. It could be a bad design, bad manufacturing process, EMC, or any number of issues.

A quick and dirty test is to short the inputs with a plain copper wire or perhaps a 10 ohm resistor. The thermocouple controller should indicate the current ambient temperature. If it does not, the controller is likely at fault, subject again to environmental aspects. Ie thermocouples are low level signals, and unless the controller is significantly hardened, it doesn't take much to throw a wrench into the works.

mnphysicist
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Re: PID Thermo controller

Postby mnphysicist » Wed Mar 02, 2011 7:40 pm

One other possibility since the unit is likely built at lowest possible cost.

If the pcb's are not properly cleaned... and IPC specs can be useless when it comes to low level signals, it is quite possible leakage currents across the PCB are raising havoc. Usually in final production test, thermocouple emulators will catch this. However, in the interests of saving time and money, its not unusual to find shortcuts which may allow a unit to pass the test, but still crash and burn in the field. I've seen well intended purchasing agent calls which dick with the solder mask, plating on input terminals, and even the laminate in general raise havoc. The same can be said concerning production issues. Its easy to build five-ten units, but another story entirely to run half a million.

Another possibility is the triboelectric effect. Stresses on the pcb assembly can and do raise havoc if processes are a bit out of whack when the unit is produced. A cold/contaminated solder joint on the input terminals, or in the vicinity of the 1st stage op amp can serve as a pretty nifty tribo, or even galvo voltage source. Its a similar deal with changing pcb vendors, board stress due to tolerance build up can bite one fast.

Sebas83
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Re: PID Thermo controller

Postby Sebas83 » Fri Mar 04, 2011 6:48 pm

Gotcha.

Upon inspection, when I bridge the TC terminals, I get an overrange reading. Open, I get a 750-850 reading. I would agree with you about the issues, but the "havoc" is repeatable and consistent even across two unique units.

I am suspect of the whole product line at this point. I think I am just going to jump to the CD101. There are at least a few articles online about it!! Ha!

Thank you very much for your help. I am going to tinker for a bit more and if it still fails, I'm sending it back.

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mightyohm
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Re: PID Thermo controller

Postby mightyohm » Sat Mar 05, 2011 10:43 am

I have been trying to keep track of cheap PID controllers on the wiki:

http://mightyohm.com/wiki/resources:pid

The Auber is probably the 2nd cheapest, after the CD101, and people seem to be using them a lot in cooking machines like espresso coffee makers and BBQ setups.

There's a page dedicated to the CD101 since I noticed it was hard to find documentation on some of the hidden settings:
http://mightyohm.com/wiki/resources:cd101

The C100 isn't on the list, it might be worth adding a link with a caution about the problems you are experiencing.

Dnadnnoid
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Re: PID Thermo controller

Postby Dnadnnoid » Sun Mar 06, 2011 8:16 pm

hey everybody, ive been trying to find more detailed information on programming this controller since i built my kiln controller a few weeks ago with a cd101. this is the only place ive found where ANYBODY is actually talking about it! :P

i have already programmed it to K type thermocouple, display farenheit and reset the max temp it will read. i also messed with a lot of other settings in my initial attempts to figure it all out and probably changed a few variables i probably shouldnt have.

as it is right now the max temp is set to 1372 so i can get my kiln as hot as i need it to be (1050-1100 for a glass annealer) im using it to controll a relay that turns on the elements to my kiln. im not using the #5 and #6 outputs. i was told it would be better to use the internal relay (#4 and #5) as a switch to turn on the main relay since it has a 120v coil.
it seems to work just fine this way but it will turn on the relay for about 30 seconds and then off for 1 second and so on like that.. i would like to change this so its on constantly until it reaches the set temp and just turn of and on as it needs to in order to keep that temp.

also id like to set it to be able to use the 5 and 6 output terminals in case i decide to use a different relay anytime in the future, i was measuring the output a couple days ago with my multimeter and THERE IS NO OUTPUT! the internal relay works fine however. i want to turn that on when i need to.


if someone could please tell me what settings to change in order to do these things i would be much appreciative!!

my controller serial number is FK02-M*AN--NN ZK-1018

thanks in advance for ANY insight you can give me!

Dnadnnoid
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Re: PID Thermo controller

Postby Dnadnnoid » Mon Mar 07, 2011 7:08 pm

ok now ive totally screwed it up. i tried messin around with it again today.... i have no idea what im doing or how to get it back the way it was

Dnadnnoid
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Re: PID Thermo controller

Postby Dnadnnoid » Wed Mar 09, 2011 9:49 am

sorry i killed the thread. :?

i got it all fixed. i spent about 5 hours searching the web and finally found some good info after looking up the sous vide slow cooker set-up

i also found a good manual. it doesnt describe the cd101 but the cb100 looks nearly identical and the programming seems identical to the cd101. someone could take a look and add it to the wiki maybe?

http://www.rkcinst.co.jp/english/pdf_ma ... cb25e3.pdf

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mightyohm
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Re: PID Thermo controller

Postby mightyohm » Wed Mar 09, 2011 10:41 am

Sometimes it takes me a bit to catch up on these posts, sorry. :D

It's best not to arbitrarily change the internal settings without first recording them. I did this when I first got my CD101, so if I get a chance I'll add the defaults to the wiki.

The manual you found does look interesting, because it documents the self-tune function, which I have not seen explained in any of the CD101 manuals I have.

So how did you you get the controller to do what you wanted? I think what you are looking for is commonly called "on-off mode", and acts like the thermostat in your home. The heater is turned on continuously until the temp reaches the set point, then it turns off until the temp drops some number of degrees below the set point. The Omega PID controllers I have used have this feature, but I don't know how to enable it on the CD101.


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