PID Thermo controller

Discussion about events, resources, or any topic not related to one of the project forums below.
Dnadnnoid
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Re: PID Thermo controller

Postby Dnadnnoid » Wed Mar 09, 2011 9:40 pm

i basicly used this http://www.lesmarmitonsnj.com/Sous-Vide ... ttings.pdf but i used my own settings for the thermocouple type and min/max temp limits. also i turned on SL6 by setting it to 1. that turns on the internal relay (which i need) and set it to read farenheit by turning on SL2. (set it to 1)

i think the real key is to just make sure you have auto-tune turned on and it basicly does the rest for you.

i also experimented with the COD setting (i think i set it to 0010. the manual i have only lists 0000, 1000 and 0001 as options) and found a few other functions not documented in any of the other manuals i found online. i didnt change any of those though. figuring i wouldnt know what i had changed anyways... i think it may have to do with setting the decimal point.

i dont plan on messing with it anymore but i do plan on making another controller for another kiln in the future. so before i program the new one i think i'll do some exploring

KayDat
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Location: Melbourne, Victoria, Australia

Re: PID Thermo controller

Postby KayDat » Wed Apr 06, 2011 6:18 pm

Similar to Sebastian, mine is an eBay "REX-C100", actually labelled RKC Tokyo Japan (pfft yeah right). Came with Chinese instruction sheet, and unable to access Initialization Mode (or so called "Secret Menu"). Shift+Set doesn't access Initialization Mode, and after several hours of fiddling, I think it might be completely inaccessible. I had actually bought this back in November, but never got around to wiring it up till yesterday.
There are many manuals online, the one linked by Dnadnnoid is probably one of the better ones (seeing as it's actually RKC and all). Here are links to some other ones I've found:

For my PID (probably the same as Sebastian's), the normal configuration menu only comes with the following options:
    AL1 (Alarm)
    AL2 (Alarm)
    SC (Temperature offset)
    ATU/ARU (Auto-tune)
    P (Proportional band)
    I (Integral time)
    D (Derivative time)
    R (Cycle time/Control output cycle/heat-side proportioning cycle)
    LCK (Settings lock)

LCK was defaulted to 0000 instead of 0100 as mentioned in the C100 manuals. Setting LCK to anything but 0000 results in locked settings, but SV can always be set. Although the LCK setting is four digits, the maximum setting is 0255. This means you can't follow the two main ways of accessing the Initialization Menu that I've found from scouring the web (setting the LCK to either 0000 or 1000).

Although my temperature reading was indeed off when I first set it up, I managed to calibrate it to boiling water, and set my SC to -16°C. Even after calibration, I found at roughly room temperature, temperature was ~5°C lower than ambient. Not too sure why this is the case (Metal probe? Inaccurate below certain temp?) but at the temperatures I want for sous-vide, I found it was spot on, at least according to my cheap Chinese cooking thermometer from Deal Extreme.

My PID model number is FK02-M*AN ZK-1033, similar to Dnadnnoid. I'm not sure what ZK-1033 is, but according to the user manuals, this means it is "PID action with autotuning (Reverse action)", K type thermocouple range from 0-400°C, relay contact, Deviation high alarm for alarm 1, and no alarm 2. I found if I leave the thermocouple (TC) disconnected, the PID reads overscale. I noticed though, that when I first hooked up my TC to my PID, the connection was faulty, and the PID erratically went between overscale and reading the temperature. Turns out the positive terminal of the TC wasn't crimped properly, so I soldered the wire onto the terminal properly.

For reference, according to the user manual these are the default settings (nope I didn't write it down before I started fiddling either, except for alarms which I haven't touched):
    AL1 (200)
    AL2 (0)
    SC (0)
    ATU/ARU (0)
    P (3.0)
    I (250)
    D (50)
    R (20)
    LCK (0000)

User manual that came with my PID, for reference. http://www.scribd.com/doc/52460071
Last edited by KayDat on Thu Apr 14, 2011 12:31 am, edited 1 time in total.

KayDat
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Joined: Wed Apr 06, 2011 5:41 pm
Location: Melbourne, Victoria, Australia

Re: PID Thermo controller

Postby KayDat » Wed Apr 06, 2011 6:47 pm

By the way, if anyone actually wants to know what PID is and how it works, I found this is a fantastic guide that explains what PID is. Just replace the set of five pics about automatic reset (Integral) with this when reading. While their diagram is correct, I found it confusing that they have all images centered on the P-band as opposed to Set Point. This really is a fantastic guide and explains what PID is very well. Highly recommended read.
Auber also explains why you shouldn't set cycle time (the R value in the settings) to 1s if you're using a solid state relay (SSR).

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mightyohm
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Re: PID Thermo controller

Postby mightyohm » Thu Apr 14, 2011 12:14 am

KayDat,

Thanks for posting the "REX-C100" info, I'm sure it will be very helpful to other PID hackers!

KayDat
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Joined: Wed Apr 06, 2011 5:41 pm
Location: Melbourne, Victoria, Australia

Re: PID Thermo controller

Postby KayDat » Thu Apr 14, 2011 9:52 pm

Cracked open the "C100", I'll post up some photos soon. For those who aren't afraid of doing some soldering, this cheap model can actually be modified to do stuff you'd have to pay more for. Things I've figured out so far:
220VAC transformer drops to 12VAC and 10VAC, which then go to bridge rectifiers to convert to DC. 12VDC goes to relays (alarm and output relay), 10VDC goes to a 78L05 5V regulator, which then goes to logic. This means you can buy the cheap Chinese knock-off, and mod it to run off 12V instead of mains 220V. Alternatively, you can replace the mains transformer to run off 110VAC if you wish. (I noticed that the 12V output was closer to 13.1V and the 10V was closer to 11V. My mains power runs at 240VAC, which is roughly 9% higher than 220VAC, which explains the slightly higher voltage)
These cheap knock-off models don't directly support SSR output, but since the internal relays run off 12V, you can pull the controlled 12V to the output relay and wire it straight up to an external SSR.
Although these models only support K thermocouples, there are three contact points on the PCB, just like models that support PT100. Perhaps it's possible to mod it to unlock the initialisation mode, to allow changing of thermocouple type?

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mightyohm
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Re: PID Thermo controller

Postby mightyohm » Tue Apr 19, 2011 12:31 pm

KayDat wrote:Cracked open the "C100", I'll post up some photos soon. For those who aren't afraid of doing some soldering, this cheap model can actually be modified to do stuff you'd have to pay more for. Things I've figured out so far:
220VAC transformer drops to 12VAC and 10VAC, which then go to bridge rectifiers to convert to DC. 12VDC goes to relays (alarm and output relay), 10VDC goes to a 78L05 5V regulator, which then goes to logic. This means you can buy the cheap Chinese knock-off, and mod it to run off 12V instead of mains 220V. Alternatively, you can replace the mains transformer to run off 110VAC if you wish. (I noticed that the 12V output was closer to 13.1V and the 10V was closer to 11V. My mains power runs at 240VAC, which is roughly 9% higher than 220VAC, which explains the slightly higher voltage)
These cheap knock-off models don't directly support SSR output, but since the internal relays run off 12V, you can pull the controlled 12V to the output relay and wire it straight up to an external SSR.
Although these models only support K thermocouples, there are three contact points on the PCB, just like models that support PT100. Perhaps it's possible to mod it to unlock the initialisation mode, to allow changing of thermocouple type?


I have often wondered if just tapping off the relay coil would let you run a SSR on models that don't support one out of the box. It would be helpful if the software enabled you to adjust the cycle period down to 1-2s - I'm not sure what the relay models run, but it's probably much longer than that to avoid burning out the contacts prematurely.

I know that the CD101 can be set to any thermocouple type via a hidden menu, but I don't know if the internal circuitry is the same for all types, so it may not actually work as expected.

tek1229
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Joined: Sat May 07, 2011 4:24 pm

Re: PID Thermo controller

Postby tek1229 » Sat May 07, 2011 4:35 pm

Hi, I just found this post about the REX-C100 after mine showed up the mail and I couldn't read chinese, I needed some info..

Anyways, I had the same trouble as the original poster with over temp and erratic readings with a k type thermocouple.. Where I purchased it stated it was 100-240 volts... Nope, that was wrong, The voltage coming out of the transformer going into the 5 volt regulator was way too low and it wouldn't read accurately at all.. Once hooked up to 220 volts it worked fine.. Since I had a desire for 120 volt operation I replaced the transformer with another one from scrap that had approx 13 volts and wired as required to feed the regulator and coils/relays.. Been running good for 5 hrs now.. Was worried about sharing transformer output with the relays but seems to run great..

Anyways, Sebas83 make sure your running it off 220-240 volts to get accurate readings..

keith20mm
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Joined: Thu May 19, 2011 2:27 pm

Re: PID Thermo controller

Postby keith20mm » Thu May 19, 2011 2:47 pm

KayDat wrote:Cracked open the "C100", I'll post up some photos soon. For those who aren't afraid of doing some soldering, this cheap model can actually be modified to do stuff you'd have to pay more for. Things I've figured out so far:
220VAC transformer drops to 12VAC and 10VAC, which then go to bridge rectifiers to convert to DC. 12VDC goes to relays (alarm and output relay), 10VDC goes to a 78L05 5V regulator, which then goes to logic. This means you can buy the cheap Chinese knock-off, and mod it to run off 12V instead of mains 220V. Alternatively, you can replace the mains transformer to run off 110VAC if you wish. (I noticed that the 12V output was closer to 13.1V and the 10V was closer to 11V. My mains power runs at 240VAC, which is roughly 9% higher than 220VAC, which explains the slightly higher voltage)
These cheap knock-off models don't directly support SSR output, but since the internal relays run off 12V, you can pull the controlled 12V to the output relay and wire it straight up to an external SSR.
Although these models only support K thermocouples, there are three contact points on the PCB, just like models that support PT100. Perhaps it's possible to mod it to unlock the initialisation mode, to allow changing of thermocouple type?


Hi KayDat,

I have one of these knock-off Rex-C100 PID controller, that I intend to operate on 220vac main, with SSR output for heater element control, and a K-type thermocouple. The thermocouple came with the PID controller.

You mention that the SSR output can't be directly controlled from the screw terminals, but that I could take the output relay 12V to the relay secondary.

Looking at the label on unit's right side, is listed, beginning upper left of label:
1 AC 220V
2 AC 220V
3 OUT (my note: the illustration on the label seems to indicate that this is a common between 4 and 5, as if 4 is NO and 5 is NC
4 +
5 -

Beginning at upper right of label
6 AL1
7 AL1
8 IN (and if label is correctly oriented to back screw terminal layout, this is an empty hole, no terminal)
9 -
10 +

On the backside terminal area, all 5 'left' screws present, right side, upper 2 are present, next down missing, and lower right 2 present.
The middle 2 upper and 2 lower screw positions are empty.

First, is this the layout you have on your PID controller?

Next, using the apparent orientation, upper left 2 screws are main power, next lower 3 are relay output common, relay Normal Open, relay Normal Closed,
upper right 2 screws just a relay contact pair, AL1, presumably, Normally Open, and lower right 2 screws for thermocouple - and +.

Does this description match what you have on your PID controller?

And, finally, if I look inside this thing, and find the NO/NC relay, then what you are describing appears to be to provide a jumper from the relay coil + over to the #4 screw terminal, but remove the relay to 3, 4, 5 screws.

Is this what you did, so that you'll have a 12v+ to screw terminal 4, to operate the SSR primary (3-30vdc), and that screw terminal 5 be ground, for the SSR ground terminal.

Thanks in advance..

If you did take photos of your PID I hope you have an opportunity to post them.
Last edited by keith20mm on Sat Jul 11, 2015 8:23 am, edited 1 time in total.

keith20mm
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Joined: Thu May 19, 2011 2:27 pm

Re: PID Thermo controller

Postby keith20mm » Fri May 20, 2011 7:39 am

I examined the circuit board and it looks like there's a couple of ways to set this up.

Here's what I altered, to provide SSR output:

Image

This disconnects the #3 screw terminal trace tab from the relay secondary common, converts the #3 screw terminal trace to the - SSR output by taking the #3 terminal trace to ground, routes +12 to the relay common pole from the +12VDC trace at relay coil.

Note that the screw terminal #5 is +12VDC when the relay coil is non-energized.

If you need +12VDC always, and very little current is required, you can cut through the #5 screw terminal trace, between the relay pin and the slightly outboard via, and then connect the +12VDC from either the relay coil power pin or the, now, powered relay common pole pin.

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mightyohm
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Re: PID Thermo controller

Postby mightyohm » Tue May 24, 2011 12:42 pm

I figured that it would be possible to convert a PID to SSR output in this way, but I've never needed to do it. Nice work. :D


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