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MarkMc
science forum beginner
Joined: 13 Jul 2005
Posts: 3
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 Posted: Wed Jul 13, 2005 10:01 am Post subject:
Help setting up OMRON PID Controller
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Hi
I'm a complete newbie to control systems.
I just got an OMRON temperature controller, model number E5CS-R1KJX.
The manual which comes with it is not much use to me
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 heating 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 |
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HoPpeR© trading at 1492¥
science forum beginner
Joined: 09 Jul 2005
Posts: 46
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| Posted: Thu Jul 14, 2005 1:27 am Post subject:
Re: Help setting up OMRON PID Controller
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On 13 Jul 2005 05:01:36 -0700, "MarkMc" <mmcnospam@yahoo.co.uk>
proclaimed to the world:
| Quote: | Hi
I'm a complete newbie to control systems.
I just got an OMRON temperature controller, model number E5CS-R1KJX.
The manual which comes with it is not much use to me
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 heating 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?
|
PID is a type of control action. It is best for maintaining an
accurate setpoint. On/Off has a range defined by the temperature at
which the output comes on to heat and the temperature where it goes
off. The amount of the band has to be big enough to not damage or wear
out the devices that are used to heat and cool.
| Quote: |
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?
|
You need to provide a power connection that is breaker protected and
has an on/off switch.
| Quote: |
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?
A thermocouple is two wired made of different metals connected to each |
other. There is a small voltage produced that is proportional to the
difference between the temperature at the tip where the two wires are
connected and the open end. You must use thermocouple wire all the way
to the controller so that you can measure the temperature at that end.
Simple.
What is not simple is going through all the programming that you must
do by the keyboard to get this set up right. I would also have to know
things like what you are using to heat and cool with.
Omeron's manuals are not easy for someone inexperienced to use. It
would take a good amount of time for me to walk you through the
process. Time that many of us here charge for IRL.
Be well,
HoP
The preceding message represents personal opinions
and/or advice that may prove incorrect or harmful. But then maybe not.
Feel free to disregard.
------- Words have no Warranty ------
------- No View without Merit ------ |
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Usenet user
science forum Guru Wannabe
Joined: 06 May 2005
Posts: 166
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| Posted: Thu Jul 14, 2005 6:19 am Post subject:
Re: Help setting up OMRON PID Controller
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On 13 Jul 2005 05:01:36 -0700, "MarkMc" <mmcnospam@yahoo.co.uk> wrote:
| Quote: | Hi
I'm a complete newbie to control systems.
I just got an OMRON temperature controller, model number E5CS-R1KJX.
The manual which comes with it is not much use to me
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 heating 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
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I wouldn't have thought that fermentation required the accuracy of a PID
temperature controller. PID systems use negative feedback of an error signal
(difference between actual and desired temperature) which is then amplified
proportionally (P), and/or integral (I) and/or differential (D) in varying
amounts to compensate for thermal lag etc. A correctly tuned system will
maintain a temperature within very fine limits, say + or- 0.1 Degs C.
A normal bimetallic thermostat should serve your purpose quite well, controlling
a heated blanket or tray in contact with the fermentation vessel, or maintain
the air in the fermentation room at the desired temperature with suitable fans
to ensure mixing.
I you want to use the thermocouple PID system, thermocouple extension cable
should be used, available from suppliers such as RS Components.
http://rswww.com/cgi-bin/bv/rswww/subRangeAction.do?cacheID=uknetscape
JPG |
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MarkMc
science forum beginner
Joined: 13 Jul 2005
Posts: 3
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| Posted: Thu Jul 14, 2005 7:35 am Post subject:
Re: Help setting up OMRON PID Controller
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Thanks for coming back to me about this.
Perhaps I don't need PID. I can't see any way of feeding back any error
to the unit.
The main control is to turn on a flash chiller. This is a small
refrigeration unit with a built-in recirculating pump, and is used
normally under the bar to chill beer as it is dispensed.
I have a copper heat exchanger in my fermenter, and fluid gets pumped
through this and via the chiller and recirculated to bring the
temperature down - it's quite a common technique in brewing circles I'm
lead to believe.
Regards,
Mark
For heating (I assume I run this from the alarm? 1A *should* be ok
IIRC) I'm going to use a standard 10g heating belt from a home brewing
shop.
So if I want say to keep fermentation down to about 18C, what should I
set the uppper and lower limits to? 17C and 19C?
Regards,
Mark |
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fulliautomatix
science forum beginner
Joined: 01 May 2005
Posts: 34
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| Posted: Thu Jul 14, 2005 10:38 am Post subject:
Re: Help setting up OMRON PID Controller
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MarkMc wrote:
| Quote: | 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 internet can
there are simple tuning guides for heater loops out there that will give
you a good result
without reading the book on your controller...usually PID loops have an
analogue output fed to an analogue contactor...presumably this is built
in to the unit
cooling?...not likely...power input to the heaters will reduce as
process value reaches the set point to maintain a stable temperature
or wildly unstable
tuning the controller to the process is the art of it
find the autotune button and use it! |
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Jerry Avins
science forum Guru
Joined: 03 May 2005
Posts: 534
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| Posted: Thu Jul 14, 2005 1:37 pm Post subject:
Re: Help setting up OMRON PID Controller
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JPG wrote:
...
| Quote: | I wouldn't have thought that fermentation required the accuracy of a PID
temperature controller. PID systems use negative feedback of an error signal
(difference between actual and desired temperature) which is then amplified
proportionally (P), and/or integral (I) and/or differential (D) in varying
amounts to compensate for thermal lag etc. A correctly tuned system will
maintain a temperature within very fine limits, say + or- 0.1 Degs C.
|
It may be overkill for beer, but pharmaceutical fermenters require tight
control for consistency. Typically, RTDs are used. It may be possible to
maintain +/- .1C with a thermocouple, but in practice it isn't possible
to know +/- .1C of what without frequent recalibration against a
standard and conversion cures updated to that. My most challenging
high-temperature system was a set of six liquid-phase epitaxy diffusion
furnaces operating at varying temperatures just short of 2000C that
would produce the same product from a given recipe. An error of .5C made
the product worthless. I was able to provide that all furnaces ran the
same temperature profiles, but the actual temperature wasn't known.
| Quote: | A normal bimetallic thermostat should serve your purpose quite well, controlling
a heated blanket or tray in contact with the fermentation vessel, or maintain
the air in the fermentation room at the desired temperature with suitable fans
to ensure mixing.
|
I'm sure a professional brewer could make do with that, but beginners
need the best tools. A bimetallic thermostat should have adjustable
hysteresis and needs a variable anticipator. (Home thermostats have
variable anticipators and work poorly when those are not properly set.
Computerized house thermostats do anticipation electronically and adjust
themselves. They work with less overshoot after a few hours of
operation.) I might not have chosen that particular controller (in fact,
I would probably have built my own), but having it, I would use it.
| Quote: | I you want to use the thermocouple PID system, thermocouple extension cable
should be used, available from suppliers such as RS Components.
|
Many thermocouples are a few feet long. If the controller is close to
the fermenter, you may not need an extension. You do need a matching
plug or an appropriate terminal block (This already on the controller,
come to think of it). You need a good electronic cold junction. (You can
make one of those, but it too may be built into the controller.) All in
all, I would use an RTD at those temperatures if the controller supports
it. You can use any wire with a 4-wire connection and no cold junction
is needed. (There are 3-wire RTDs too.)
This gave me an error page. What was it intended to show?
| Quote: | http://rswww.com/cgi-bin/bv/rswww/subRangeAction.do?cacheID=uknetscape.JPG
|
Had you asked what to get, you might have been given different advice.
Given that you have what you do, you need information on how to use it.
One tip that many don't realize has to do with sensor placement relative
to the heat source and the controlled material. It doesn't apply to
stirred liquids, but you may eventually use your controller for another
purpose (enameling furnace?), and you probably won't stir. In many
systems, there is a time lag between the heater's changing temperature
and the load's response to it. The obvious way to stabilize such a
system is differentiation; that's classic. In many thermally regulated
systems, by the time the load responds at all an excessive amount of
heat may already have been pumped in. Especially when there is
insulation surrounding the regulated chamber, the response to a step
input can be more like the output of a delay line than a simple
exponential rise. Placing the thermocouple in an appropriate place
between the heater and the load provides some D term with no electronic
help and often with increased stability. A little D more from the
electronics is usually best.
Systems that don't need to respond quickly to step commands work well
with very little integrator gain. The integrator will settle on the
right level eventually, and that's all that matters. Is such a case, it
comes clear why the integrator gain is called "Reset". That literally
means "set again", i.e., change the setpoint. That's all the integrator
needs to do.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ |
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Jerry Avins
science forum Guru
Joined: 03 May 2005
Posts: 534
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| Posted: Thu Jul 14, 2005 2:13 pm Post subject:
Re: Help setting up OMRON PID Controller
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MarkMc wrote:
| Quote: | Thanks for coming back to me about this.
Perhaps I don't need PID. I can't see any way of feeding back any error
to the unit.
|
You don't send an error back to the controller. You tell the controller
what temperature you want (called the "command" and give it a way to
measure the actual temperature. The difference is the error. Error is
determined and used internally by the controller and used in its control
algorithm. Unless the error gets too large, it's not your concern.
| Quote: | The main control is to turn on a flash chiller. This is a small
refrigeration unit with a built-in recirculating pump, and is used
normally under the bar to chill beer as it is dispensed.
|
That kind of on-off operation will be difficult to stabilize. It would
be better to use a variable-speed motor so the controller can adjust the
rate of cooling.
| Quote: | I have a copper heat exchanger in my fermenter, and fluid gets pumped
through this and via the chiller and recirculated to bring the
temperature down - it's quite a common technique in brewing circles I'm
lead to believe.
|
Find out from other brewers how they control it. Ignore any advice you
get here.
| Quote: | For heating (I assume I run this from the alarm? 1A *should* be ok
IIRC) I'm going to use a standard 10g heating belt from a home brewing
shop.
|
The alarm is another on-off device. On-off controls necessarily produce
limit cycles. it is the designer's task to make the cycle's amplitude
small enough. If You're going to use on/off for the pump anyway, do that
with the on/off alarm and use the proportional control for heat.
| Quote: | So if I want say to keep fermentation down to about 18C, what should I
set the uppper and lower limits to? 17C and 19C?
|
That depends on how small you can keep the limit cycle. Upper and lower
limits are not the same as upper and lower boundaries of the
proportional band. If you do no proportional control at all, you don't
need a proportional band (or a PID controller).
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ |
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John Popelish
science forum addict
Joined: 19 May 2005
Posts: 83
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| Posted: Thu Jul 14, 2005 2:25 pm Post subject:
Re: Help setting up OMRON PID Controller
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MarkMc wrote:
| Quote: | Thanks for coming back to me about this.
Perhaps I don't need PID. I can't see any way of feeding back any error
to the unit.
The main control is to turn on a flash chiller. This is a small
refrigeration unit with a built-in recirculating pump, and is used
normally under the bar to chill beer as it is dispensed.
I have a copper heat exchanger in my fermenter, and fluid gets pumped
through this and via the chiller and recirculated to bring the
temperature down - it's quite a common technique in brewing circles I'm
lead to believe.
Regards,
Mark
For heating (I assume I run this from the alarm? 1A *should* be ok
IIRC) I'm going to use a standard 10g heating belt from a home brewing
shop.
So if I want say to keep fermentation down to about 18C, what should I
set the uppper and lower limits to? 17C and 19C?
If you use alarm contacts to do full heat, full cool decisions, |
without benefit if the PID algorithm, he limitation on how close you
can put the two decisions is the overshoot you get after you turn off
the heating or cooling process.
If the fully hot blanket continues to heat the liquid enough to raise
its temperature 2 degrees, after the heat is turned off, then you set
up will trigger the cooler, each time the heat turns off. If the
cooler also has at least a 2 degree overshoot, it will do the same
thing for the heater, and you will have endless echoes. So some
experimentation is in order. |
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MarkMc
science forum beginner
Joined: 13 Jul 2005
Posts: 3
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