PID Thermo controller

Discussion about events, resources, or any topic not related to one of the project forums below.
geekystar
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Joined: Fri Feb 10, 2012 4:20 am

Re: PID Thermo controller

Postby geekystar » Fri Feb 10, 2012 5:55 am

Also, it took me long time to figure out how to enter into the 'secret' menu. Here is how for those who couldn't get in.

After setting LCK to 1000, do NOT press the SET and SHIFT key together now. You need to hold SET to go back to the temperature display. Then hold SET and SHIFT together for a few seconds.

Hope this will help someone.

gs

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mightyohm
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Re: PID Thermo controller

Postby mightyohm » Sun Feb 12, 2012 9:54 pm

geekystar wrote:
The working cycle T is default to 20s as this is for relay. If I change it to 2s, it will give more precise control. But will this cause fire hazard? I am not sure how much inter-phase switching is there, and whether it will cause inductive load in cables around the house and cause fire. Do I need a filter installed on the mains cable to filter out the noise? Or does T=2s means that the fastest switching time is 2s?


I don't think 2s will cause a fire hazard. I have my hotplate SSR set for 1s intervals (with the CD101) and I have not had any problems - this is a 500W heater and a large (20A?) SSR.

sideshowbob
Posts: 1
Joined: Thu May 03, 2012 1:36 am

Re: PID Thermo controller

Postby sideshowbob » Thu May 03, 2012 1:38 am

Hi, I recently bought a REX-C100 clone as well from china and just finished wiring everything. I downloaded the instructions for the original Japanese model but it's quite different to my PID considering that it's only a copy... Also I removed the built in SSR and installed an external one because the built in one would not be able to handle the load.

The PID is triggering the SSR and my Gaggia Baby 06 just fine with a stable increase in temperature.

BUT, it will not auto-tune... When I turn on the auto tune feature the external light blinks but after 20 to almost an hour nothing happens it does not turn off and just still blinks and there are no changes in the stock parameters.

When I enter a set value like 100C the temperature sometime stays at 105C or even reaches 130-140C

I suspect because if the fact that the built-in ssr was removed the auto-tune feature is not functioning, that only leaves me to manually tune the PID which I am not good at...

Can someone please give me the parameters for their PID so I will have a basis...
some parameters I have changed base on reading some forums here and there and reading the vague instructions but most of them I really have no idea what to put

Currently here are my Parameters:

SYMBOL = NAME = VALUE
SV = Setting Value = 105
AL1 = Alarm 1 = 130
P = Proportional Band = 6
I = Integral Time = 120
d = Derivative = 23
Ar = Anti-reset Windup = 50
r = Heat-site proportioning Cycle = 20
Sc = ?? = 0

Secondary Parameters:
SYMBOL = NAME = VALUE = DESCRIPTION
SL1 = input type selection = 1 = K type input
SL2 = temp unit and cooling type = 0 = Centigrade, Air Cooling
SL4 = Alarm Type Selection = 1 = Deviation High Alarm
SL10 = ?? = 1 = ??
Cod = ?? = -1 = ??


THANKS! :D

kfbcomm
Posts: 1
Joined: Mon Sep 10, 2012 8:04 pm

Re: PID Thermo controller

Postby kfbcomm » Mon Sep 10, 2012 8:11 pm

Hi Folks,

Newbie here. I have just got one of these C100s and found it won't work with an SSR. Not being very confident about making the mods that are described here is there some way I can use the standard relay function as it is.

I am trying to control a slow cooker which only draws 300 watts @ 240 volts (so less than 1 AMP if I understand correctly). Can I use the C100 for this. I have wired up the unit and got it working in terms of switching based on temperature, however when the "Out" light comes on I can't detect anything on 3,4 or 5 either DC or AC.

Any suggestions gratefully received

Thanks

Kevin

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mightyohm
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Re: PID Thermo controller

Postby mightyohm » Sun Sep 16, 2012 3:37 pm

I'm not familiar with the C100, but you won't "see" any voltage on the relay pins unless you connect power to the relay 'common' terminal. How do you have the controller wired?

loetz
Posts: 2
Joined: Tue Oct 02, 2012 6:33 am

Re: PID Thermo controller

Postby loetz » Tue Oct 02, 2012 6:55 am

Hey, All:

I'm having some problems with my REX-C100 as well. I'm not really sure if this is the right forum for this discussion, but a lot of people seem to be talking about it here... so here it goes...

For example I'll set the 'set value' to 66, it will heat the water up to that level and then the 'present value' display will read as if it is holding a steady temp at 66. Afterwards I'll raise the set value to 75, and instantly the present value temperature reading will increase dramatically. So while displaying that it was holding a temp at 66, it was actually increasing the temperature of the water and it doesn't show the actual temperature until the SV has been changed.

I have no idea what is going on here. Do any of you know what it could be?

Here are some pictures of my box:
http://i43.tinypic.com/33uzsr6.jpg
http://i44.tinypic.com/nmjig4.jpg
Note: I hadn't calibrated the temperatures yet in this picture, so that's why the PVs for the three PIDs are all reading different room temperatures. And, yes, I know the middle one isn't currently connected to an SSR.

Check out this video for an example of what I am talking about:
http://youtu.be/SAPQVwNdjV8?t=30s

In this next video, I tinker with the SV some more to narrow down which temperatures will cause the controller to misread the PV.
http://www.youtube.com/watch?feature=player_embedded&v=kbVs1Bs1di8
Between 10-30°, I'm getting a consistent PV reading.
10.3° SV = 42.9° PV
20.3° SV = 42.9° PV
30.3° SV = 42.9° PV

When I hit 40° (close to the actual temperature, but a little under) the PV reading drops 2°.
40.3° SV = 40.9 PV

If I set the SV over the real reading, it goes back to reading the normal PV.
50.5° SV = 42.9 PV

Lastly, I demonstrate that the reading gets more and more off the closer I get to the real temperature reading.
33.3° SV = 42.8 PV
35.3° SV = 42.4 PV
37.3° SV = 41.9 PV
39.3° SV = 41.5 PV

___________________________________________________________________________________________________________________________________

All of my PIDs are having this same problem, and I have tried swapping the probes. Maybe it is something that could be adjusted in the settings.

If it helps, here is a copy of the manual and a transcription of all of the PID's current settings:

http://www.rkcinst.co.jp/english/pdf_ma%20...%20zc21e1.pdf

Option -Setting- Explanation
AL1 -000.0- Alarm 1
ATU -0000- Auto-tune
P -12.3- Proportional Band
I -88- Integral Time
d -22- Derivative Time
AR -51- Anti Reset Wind-up
T -2- Heat Side Proportioning
SC -000.0- ????
LCK -1000- Set Data Lock

after the lock I get these options with these settings:

Option -Setting- Explanation
COD - 0000 - ????
SL1 - 1000 - Input Type
SL2 - 0000 - Temperature Type and Cooling Type
SL3 - 0000 - ????
SL4 - 0000 - Alarm 1 Type
SL5 - 0000 - Alarm 2 Type
SL6 - 0001 - ????
SL7 - 0000 - ????
SL8 - 0000 - ????
SL9 - 0000 - ????
SL10 - 1001 - ????
SL11 - 0000 - ????

Changing COD to 0001 brings up these options:
SLH - 100 - Setting Limiter High
SLL - 000.0 - Setting Limiter Low
PGdP - 3 - ????
oH - .2 - Differential Gap Setting
dF - 1 - ????


Other notes:
-Yes, these PIDS are the model meant for running an SSR
-Yes, I'm using pt100 probes and I have the PIDS set up for them
-Water is not getting into the probes


SO! Do any of you have any ideas as to what I could do to get these things running correctly?

ipconfig
Posts: 1
Joined: Sat Oct 27, 2012 10:13 am

Re: PID Thermo controller

Postby ipconfig » Sat Oct 27, 2012 10:44 am

hi all,
i have question about value of resistor. I damaged the PCB and now I have not two resistors in PCB. You do not know the value of the missing resistors?

Image

Thank you for your answers.
Feri

RocketMan
Posts: 4
Joined: Fri Nov 09, 2012 1:33 pm

Re: PID Thermo controller

Postby RocketMan » Fri Nov 09, 2012 4:39 pm

I purchased one of these Chinese Rex C100 clones last year off eBay to control my electric smoker. After having considerable difficulty getting it to work out of the box, I went online looking for information. This thread is one of the most informative resources I managed to find and it has proven very helpful. There is some great information available from many contributors; many thanks to all.

After finally getting my controller up and running well, I thought I'd register and pass on to the group a few of the things discovered in the process. Maybe this post will be helpful to folks having similar difficulties getting their controllers to work.

When ordered, my controller was supposed to have had these basic specs: 110-220VAC power, °C/°F display at 0.1° resolution, default type 'K' TC and programmable for others, SSR output included. What it turned out to be was 220VAC power only, fixed °C display at 1° resolution, fixed type 'K' thermocouple, and not SSR compatible. Like many others I found all this out the hard way. Oh, joy.

When first powered up the unit was very unstable. When the provided 'K' T/C was connected, the process variable reading was all over the place, running up and down the scale, sometimes giving a false open sensor indication. My first thought was it was a faulty T/C, but some further fiddling convinced me the T/C was not the problem.

With a lot of experience designing and building PID temperature controlled crystal growth furnaces, I figured this thing could be beat. Opening the unit on the bench, it was quickly determined the power supply was 220VAC only, and powering it with 120VAC caused most of the problem. As the unit had a basic linear power supply, the simplest fix was to remove its transformer and modify the controller to be powered by 12VAC. The voltage regulation circuit could handle that easily, and since the controller was going in a project box, putting a small 12 volt transformer in the box would be no problem.

The output relay was removed from the controller and its coil drive patched to two of the relay connection terminals on the controller. The relay drive could then be used to switch a 30 amp SSR mounted to a heat sink on the top of the project enclosure. That resolved the lack of SSR control problem.

The thermocouple provided with the controller was not usable with my smoker, so it was replaced with a better unit having a four inch long, 1/8th inch diameter probe. A type 'K' panel mount thermocouple connector was added to the project box, and a matching plug put on the T/C lead to make it easy to remove and clean.

Being a degrees C only controller is easily overcome by using a little temperature conversion program on a laptop. Input desired degrees F, plug the converted degrees C into the controllers setpoint, and off we go.

Connecting everything to the smoker, the controller was able maintain 'okay' temperature stability after autotuning across a span of about ±6°. Being picky from my semiconductor growth days, I wanted tighter temperature regulation than that. And, after a few actual beef jerky test runs in the smoker it was found the controller would sometimes lose control of the process, with PV swings in excess of ten degrees at times. That was not going to work at all.

While watching the controller, I noticed the display would dim at times when the SSR was firing. Opening the controller again, I noticed poor quality electrolytic capacitors had been used in the power supply. I replaced those with some good caps from my junk box, increasing the capacitance value after the rectifier section at the same time in case the voltage was a little soft going into the regulator.
The temperature swings decreased some after that, but the controller would still lose its marbles at times. Something else was wrong with the controller, it had another shortcoming that was just not obvious.

Thinking more about the dimming display, I took another look at the power supply. The regulator was one of those three terminal LM78L05 jobs rated at 100 milliamps max output. The problem had now become clear. There are eight seven-segment LED displays in the controller display. Each segment alone can take 10-12 ma. of current to light. With four displays lit at any one time while operating, the little voltage regulator could not provide enough current before limiting and its output dropping below 5 volts. With that happening, the power to the rest of the controller was unstable causing it to lose control of the process.
There were a few LM7805 regulators rated at one amp output in my junkbox, so I swapped one of those for the LM78L05, being mindful of the different pinout. It worked very well. I estimated that the controller was using about 200 ma. at any one time during operation, so a small heatsink made of a 4-40 screw, a nut and some washers was added to the regulator.
With ten times the current now available from the power supply, there is no dimming of the displays, and the process control is right where it should be at ±1° from setpoint. Several successful runs of beef jerky and some smoked meat later, the controller is working well.

edited for speelink.
Last edited by RocketMan on Sat Jul 13, 2013 1:15 pm, edited 1 time in total.

mnphysicist
Posts: 5
Joined: Wed Mar 02, 2011 7:15 pm

Re: PID Thermo controller

Postby mnphysicist » Tue Apr 23, 2013 10:39 pm

I'm thinking of ordering one of these little jobs off ebay for a couple garage apps. It looks like a cool device, especially at those incredible prices!

It seems a lot of folks are using SSR's with these and I didnt see any mention of fire prevention. It may be that most folks are using heating elements such that even at 100% power for an extended time, no damage will occur. If not, there is a real danger of catastrophic failure without some type of over temperature protection.

SSR's typically fail in shorted mode so an external overtemp device is critical if you have excess heater capacity. Even a $2 single use thermal fuse from Digiky goes a long way in preventing a lot of trouble.... albeit an actual UL or FM approved over temperature limit with reset capability can make for simpler maintenance.

Earlier in the thread, there was mention of cycle time and SSR's. If you are running a fairly heavy load with long cycle times, the SCR die bond wires get slammed across their glass transistion temps nearly every cycle, which in years past shrunk MTBF in a huge way. (Its been 10+ years since I was in the industry, so things may have changed)... but back then 30 second + PID cycle times with SCR's were a real killer.

Thierry
Posts: 1
Joined: Wed May 22, 2013 11:53 pm

Re: PID Thermo controller

Postby Thierry » Thu May 23, 2013 12:09 am

loetz wrote:Hey, All:

I'm having some problems with my REX-C100 as well. I'm not really sure if this is the right forum for this discussion, but a lot of people seem to be talking about it here... so here it goes...

For example I'll set the 'set value' to 66, it will heat the water up to that level and then the 'present value' display will read as if it is holding a steady temp at 66. Afterwards I'll raise the set value to 75, and instantly the present value temperature reading will increase dramatically. So while displaying that it was holding a temp at 66, it was actually increasing the temperature of the water and it doesn't show the actual temperature until the SV has been changed.

I have no idea what is going on here. Do any of you know what it could be?

[...]

dF - 1 - ????

[...]

SO! Do any of you have any ideas as to what I could do to get these things running correctly?


That question is quite old and maybe you already found the answer but as I look for it and didn't found anywhere on the web here is the solution :

As says Bill G. it's not a bug, it's a functionality. What a strange functionality isn't it ?

This functionality answer to a major question : how to screw up your boss who constantly asked you why that damn measurement "PV" value is fluctuating and not equal to "SV". I had a chance to work in China so I know quite well the china way of life :) The easiest answer to this fundamental question is : just tamper the "PV" value. And what is the easiest way to tamper the "PV" value ? just copy the "SV" to "PV" shown on display if real "PV" is close enough to "SV". A boss normally never touch the setpoint "SV" and will not discover the trick :)

This functionallity should be named "f..k your boss" but here it's just damed "Digital Filtering", "dF" in Short. Just put that value to 0.

I'm use to see these kind of trick in chinese PLC software but I was astonished to see this in PID controller firmware and, worst of all, activated by default.

Regards.