PID Controller

[Rats]

Any of you have a PID on your system?

[Rats]

No, I'm pretty sure is the answer. I was told before they're a PITA for homebrewing.

TX

[Metattron]

I have one like this:

http://www.ebay.co.uk/itm/Dual-PID-F-C-DIN-Digital-Temperature-Control-Controller-Thermocouple-REX-C100-UK-/400389582095?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item5d39142d0f


It's for controlling my HLT, used with an SSR and a  PT100 probe.  No problems with it so far.

[Stitch]

I have one like this:

http://www.ebay.co.uk/itm/Dual-PID-F-C-DIN-Digital-Temperature-Control-Controller-Thermocouple-REX-C100-UK-/400389582095?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item5d39142d0f


It's for controlling my HLT, used with an SSR and a  PT100 probe.  No problems with it so far.

Do you also have a run around pump on this???

[Metattron]

No, it just turns the element on and off. Don't see why you couldn't though. The one I have doesn't do timed or stepped temperature increases, probably going to use an arduino for that, when I get round to it.

[alealex]

I was using this in my Rims, controls heating element up to 3.5kW power. might not be the cheapest, but fine work.

[Beerdoh]

A PID controller is useful for the amount of control you need with your brewery. It really depends how accurate you want things to be.
A good PID controller will have two modes:
Auto mode: Where the controller turns on and off (for instance, a heating element) until it approaches the target temperature you've set it, whereby it then turns on less and less until the target is reached; the PID will then fire on momentarily as it monitors the temperature in order to maintain the target. This is best used in a hot liquor tank where you want a particular temp maintained while you are mashing in or sparging etc.

Manual Mode: In manual mode you set a duty cycle of 0 to 100%. This determines how long the element will stay on. This will likely be also linked to a solid state relay (SSR for short). So, for instance, if you set a duty cycle (DC) of 10% with the PID and your SSR has a default cycle time of 2 seconds, the element that the PID is controlling will fire for 0.2 seconds.

So, why is this useful?

Say you have a 4 or 5 kW element in your boil kettle(something very capable, if not too powerful) - when you are boiling wort you would like to control the vigour of the boil. Using Auto mode to bring to the boil would result in too rigourous a boil, and perhaps a boil over.

To avoid this, it is useful to run the PID at 100% DC in manual mode until boil is reached, and then reduce it to maintain the boil; but you have to be there to watch it.

That said, you could also use Auto mode to get the temp to just below boiling - go off and do something else; come back to it, change to manual mode (with some arbitrary DC), and control the boil to ensure there are no boil overs on the way to hot break.

So, on the pro's and con's of using a PID, they're not a PITA, they're actually really useful if you require one as they make the process more automated, and less subject to error. But, as with any equipment, it's only as good as the programmer! 
HTH