Help setting up OMRON Temp Controller

Hi

I just got an OMRON temperature controller, model number EJCS-R1KJX. The manual which comes with it is pathetic - a duff translated affair.

I want to use this unit to control fermentation temperatures for my home brewery. This involves switching on a cooling source if too hot, and switching on a heatin source if too cold to keep a stable temperature.

I have a couple of questions about setting up the controller.

I'm not sure if i need to use on/off mode or PID - I don't know what PID actually is. Can somebody explain?

The unit provides two relay outputs one for control and the other for alarm. I assume I need to provide my own relay contact protection/suppression?

Also, I accidentally bought the wrong model. I wanted the RTD model but got the thermocouple model - eBay one off, so no chance to change it. I know nothing about thermocouples. It looks like type K's are easy for me to get, but I read something about "compensating conductors" - what's this all about?

Regards, Mark

Reply to
MarkMc
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You have a lot of questions but nothing specific. Here is a place to learn about PIDS;

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Type K thermocouples are easy to find. Regards, Tom

Reply to
Tom Biasi

PID stands for Proportional, Integral, Derivative. This describes the three responses to process error that add (or multiply) to make up the controller output. Proportional response alters the output without regard to the frequency of the error. It is set either with a proportional gain constant or a proportional band constant (100/gain). Integral response is a low pass filter type response that essentially ignores short duration errors, but accumulates a large response if an error persists. It may be set with an integral gain or an integral time (reciprocal of gain). Derivative response is a sort of high pass filter that responds stronger if the error changes quickly. It is also set by either a derivative gain or time.

On/off mode just converts the PID linear output to pulse duty cycle, useful for things like resistance heaters or solenoid valves. Continuous PID control is for things like control valves that vary stem position with signal (usually 4 to 20 mA = full closed to full open or vice versa).

For a basic tutorial on PID tuning I wrote, based on watching a time based chart of process measurement and output, see:

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That is the safest bet. I doubt that you can both heat and cool with this controller. Those take dual control outputs. You may need a dual output controller that splits the output range in half, with one output controlling the amount of heating and the other output controlling the amount of cooling. You may get to use RTDs, yet.

You have to get thermocouples that match one of the set up choices for your controller.

Thermocouple signals are produced when a wire passes through a temperature gradient. Different alloys produce different voltages, so bringing a pair of dissimilar types from a couple (electrical connection between them) from the process temperature to the controller will produce a small voltage related to the difference between those two temperatures. The controller measures its own temperature and corrects for that, so that it can infer just the process temperature. If that pair of wires has to pass through significant temperature variation (relative to the controller) on its way between these two points, the two special alloys have to be maintained the whole way, for this process to work. So you normally use thermocouple extension wire if the controller is further away than the lead length, rather than using copper extension wire.

Reply to
John Popelish

Thanks for the detailed responses, I've very grateful. I'll have a read of the link too.

rather than a 12v output. How does PID work with this?

I was assuming I could use the main control as the cooler and the alarm as the heater driver. What am I missing here? IIRC the unit will let me set absolute values for both. In reality, I'll probably need to drive a cooler in summer, and a heater in winter, but it would be better to be able to control both, as the temperature can drop quite a bit over night in summer. Perhaps good insulation can take care of temperature drops over night.

Regards, Mark

Reply to
MarkMc

Hi Tom

I am a regular on r.c.b, but for some reason, I didn't think to post my question there.

Regards, Mark

Reply to
MarkMc

I use a modified Ranco mounted to a box with a Peltier cooling/heating device. I set the set points for both cool and heat. A DPDT relay reverses polarity. Most units have a "window" capability if they are classified Heat/Cool. Google 'Rec Crafts Brewing' , many of us have described what you are doing many times. Tom

Reply to
Tom Biasi

The PID operating a relay output produces a pulse duty cycle proportional to the PID numerical output. That is, if the output is

50%, the pulse will have equal on and off times (usually, you set the period as part of the set up). The alarm relay outputs come on continuously, any time the process exceeds some value you specify. No PID algorithm is involved in them.

Bidirectional control is hard with a single pulsed output.

What sort of hardware are you using for heating and cooling (hot and cold water valves to a heat exchanger, resistive heating element and peltier cooler, heat pump)?

Reply to
John Popelish

Ah, now it's starting to see what how these controllers work. Im not sure pulsing on my chiller is a good idea.

For heat I'm intending to use a standard homebrewers/wine makers heat belt (400W IIRC) and for chilling its called a recirculating flash chiller. These are used in pubs/bars to chill beer or beer lines to stop the beer frothing. Basically the chiller is a smal refridgeration unit, which chills a line which passes through it (via heat exchanger). I intend to use it to pump (build in to unit) coolant (water) through some 8mm copper pipe, in to my fermenter which has a coil (another heat exchanger), and returns back to the unit.

Reply to
MarkMc

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