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Old 12-31-2013, 04:32 AM   #1
kaz4121
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Dumb question, but should I be using hysteresis or PID mode for the following processes:
  • heat water/wort
  • heat/cool fementation fridge/keezer

How exactly is PID different from hysteresis mode? From my understanding hysteresis mode tells the BCS to turn on the output when it reaches a certain temp (+/-) and turn if off when it reaches a different temp. Is this correct? How does PID differ?
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Old 12-31-2013, 05:45 PM   #2
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Hysteresis is fine for the fermentation chamber as it works the way you said. Turns cooling on when temperature rises above the set point by the hysteresis value and turns it off when it gets back to the set point. This is fine when you don't care about a little "drift" below the set point as the temperature stabilizes between the now much colder freezer coils and the temperature probe.

PID function is different, in that the the PID will shut off the system for very short periods of time before reaching the set temperature so that the system will not overshoot, or will overshoot a minimal amount. This works well during heating, but will rapidly destroy a mechanical cooling system with too many start/stop cycles in a short time. PID basically is predictive and tries to minimize the time it takes to get to temperature without going past the set point.

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Old 01-01-2014, 04:03 PM   #3
crane
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PID works great for electric heating elements as they can be turned on/off quickly without destroying them over time. As ChuckO mentioned PID will destroy a refrigerator compressor. I don't think you can use PID for gas burners either because the flame can't ignite fast enough for the short pulses that PIDs use but I may be wrong.

 
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Old 01-01-2014, 09:19 PM   #4
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With the BCS can you set the PID cycle time? If so you could set it for say 20 seconds and you could use it to control a gas valve.
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Old 01-02-2014, 12:51 AM   #5
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Quote:
Originally Posted by crazyirishman34 View Post
With the BCS can you set the PID cycle time? If so you could set it for say 20 seconds and you could use it to control a gas valve.
You can set the PID Sample Period, not sure if that is the same as cycle time or not.
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Old 01-02-2014, 12:52 AM   #6
kaz4121
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Quote:
Originally Posted by ChuckO View Post
Hysteresis is fine for the fermentation chamber as it works the way you said. Turns cooling on when temperature rises above the set point by the hysteresis value and turns it off when it gets back to the set point. This is fine when you don't care about a little "drift" below the set point as the temperature stabilizes between the now much colder freezer coils and the temperature probe.

PID function is different, in that the the PID will shut off the system for very short periods of time before reaching the set temperature so that the system will not overshoot, or will overshoot a minimal amount. This works well during heating, but will rapidly destroy a mechanical cooling system with too many start/stop cycles in a short time. PID basically is predictive and tries to minimize the time it takes to get to temperature without going past the set point.
Thanks this answers my question! Hysteresis for ferm control and PID for heating elements!
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Old 01-02-2014, 01:08 AM   #7
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No it is how long the PID is on at 100%. So if you set it to 4 seconds and the pic needed to apply 25% power it would turn on the heat for 1 second and off for 3
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Old 01-02-2014, 01:36 AM   #8
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does this screenshot help?

it looks like you may be able to do that?

I apologize for being clueless.
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Old 01-02-2014, 01:43 AM   #9
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Yeah looks like you can set a minimum % also. That would allow you to time it so your burner has time to come on and deliver some heat. One thing we forgot to ask is are you using gas or electric heating?

I also think that you can run both your fermentation and brewing at the same time with your controller.
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Old 01-02-2014, 05:40 PM   #10
kaz4121
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Quote:
Originally Posted by crazyirishman34 View Post
Yeah looks like you can set a minimum % also. That would allow you to time it so your burner has time to come on and deliver some heat. One thing we forgot to ask is are you using gas or electric heating?

I also think that you can run both your fermentation and brewing at the same time with your controller.
I'm running electric but based the the above comments, everything got cleared up. My main concern was whether hysteresis was preferred over PID for fermentation and heating elements.

The BCS is great because it does allow for simultaneous control! My keg/serving fridge/MLT/HLT/BK/pumps/fan/fermentation fridge can all run simultaneously (if needed).

Thanks for the help guys
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