Created Date: November 07,2014

Created by: Tinker

A couple of things,

If you really only want the average temperature of your 4 thermocouples, you could do it with one channel of you input module. I turns out that if their resistances are essentially identical (lead + junction) , one can wire multiple thermocouples in parallel and automatically get the average temperature. It is quite important that the resistances are "identical ", sometimes fixed value precision resistors are added to each thermocouple to swamp any variations in individual thermocouples (connection to said resistors must be made at a point with not significant temperature gradient) Unlike your mathematical averaging, if one or more thermocouples opens you will still get the average of the remaining thermocouple (however a short outside of the measuring area will cause an error)

Of course if you have no other use for the extra channels then you might as well do it the way you are. Well, except that usually when one wants to average four values, one adds them and divides by four, not two, but I'm sure that was just a typo. (but you'll want correct that or you will always be cooling)

I'm quite sure there is no need for the "immediate " contact on X103 (_IO1_CH1_Burnout) et. al. I imagine it is unlikely the data changes any faster than the regular scan, and even if it did, you won't be able to respond faster than one scan, so the performance overhead of the immediate contacts seems unnecessary (not that I know what the performance hit is, but it has to be something). Also, in the current version you are only tuning on a light, I'm SURE you can't react to a light turning on in less than the 2 or 3 milliseconds that I suspect the scan will be. (I'd think you'd want to stop trying to control the temperature if you have a temperature module error, a N.C. Y005 in your heat and cool rungs would do it)

Other than that, it looks like a workable on/off control. You may want to check that your 2 minute short cycle prevention on the chiller does not lower the temperature enough to start heating, conceivably power wasting oscillation is a possibility.

Created Date: November 07,2014

Created by: pudland

Thanks for the reply Tinker!

A couple of things,

If you really only want the average temperature of your 4 thermocouples, you could do it with one channel of you input module.

I don't have any use for the other 3 channels. I guess I figured that I could manipulate the setup(through the logic) easier if each thermocouple was on its own channel. If one fails I can remove it from the math in the logic immediately, come back when I have more time and replace the thermocouple physically then add it back to the math. ( I guess having 4 is overkill being that I'm not running a PID for "precision " control!)

Well, except that usually when one wants to average four values, one adds them and divides by four, not two, but I'm sure that was just a typo. (but you'll want correct that or you will always be cooling)

Nice catch! I must of had a "DERP " moment there!

I'm quite sure there is no need for the "immediate " contact....

I don't know the significance of the "immediate " option... I will do my research! I removed ALL the "immediate " states in the logic.

You may want to check that your 2 minute short cycle prevention on the chiller does not lower the temperature enough to start heating, conceivably power wasting oscillation is a possibility.

I had thought about that actually!! Some folks have their chambers made from smaller fridge units. The fridge regulates itself, they separate the heating coil from the fan in the heater. The heating coil is controlled by an STC-1000 type of device while the fan always runs. So there may be times that both are running and mixing with each other. If the fridge tries to "over cool ", the heater will kick in and try to limit that.

I'm SURE you can't react to a light turning on in less than the 2 or 3 milliseconds that I suspect the scan will be. (I'd think you'd want to stop trying to control the temperature if you have a temperature module error, a N.C. Y005 in your heat and cool rungs would do it)

Wait, am I not understanding how the logic works? Will the Lamp stay on as long as there is an error? or Will it try to pulse at the scan frequency? Do I need to "set " Y005 and give myself a manual "reset "?

I added a Y005 N.C. in front of both the Heat and Cool outputs. That was a good suggestion!

Thanks!

Created Date: November 04,2014

Created by: pudland

Hello All,

I have milled around the forum looking for Click PID info. I have already read the posts and checked out the Project files the fellow members uploaded. Before I tackle a Click PID setup I figured I would try a basic logic control.

Project:

Fermentation Chamber Temp Control

1) C0-01AC -- Power Supply.

1) C0-01AR-D -- Standard Type of CPU with 8 Points AC Inputs and 6 Points Relay Outputs.

1) C0-04THM -- Thermocouple input or voltage input (16bit) x 4ch

4) THMJ-T06L06-01 -- T/C PROBE TYPE J 1 /8in OD x 6in 316SS 6ft LEADS

1) Small Wine Chiller -- I believe it only goes down to 52 Deg F. I have to double check.

1) Small Personal Heater.

The chamber will be thermally insulated of an unknown size at this time.

I am currently thinking over the layout of the 4 T/C's, 2 on the carboy, 2 out in space etc. I have the current layout in the project file.

At this point I AM NOT looking for even 2 deg accuracy. Temp swings of 55 to 65 would be tolerated. If they are less, then happy times!

If you could please look over the logic for errors in my thinking or someway has a better way, that would be greatly appreciated!!

P.S. First time using a Click PLC. I haven't messed with an AB PLC in about 10 years!

Thanks!