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-   -   PID for BK: Yes/No? (http://www.homebrewtalk.com/f170/pid-bk-yes-no-256974/)

Eighty2Fifty1 07-15-2011 03:20 AM

PID for BK: Yes/No?
 
I'm in the designing process of an electric Kal-type setup, but I'd like to make mine a little simpler. My question is, do I need to use a PID to control the element in the boil kettle, and if not, what other control options are out there? I was thinking that I could set up some sort of electric range-type to make it work (rheostat or whatever they are), since it doesn't seem like precise temp control is that necessary. Not that PID's are that expensive, but I'm curious about my options.

I'm planning a single PID for the HLT, and probably just a dial thermometer for the MLT, however we all know how the plan goes out the window after a homebrew or 7...

Yuri_Rage 07-15-2011 03:22 AM

You don't need PID for the boil. Full heat until the boil, then throttle back to a duty cycle that maintains it. No need to worry about overshoots...it's boiling!

samc 07-15-2011 03:37 AM

You don't need it, but it's nice to have as a redundant backup if and when you need an alternate brewing set up. For example you suddenly get the urge to come to the dark side and BIAB !

Eighty2Fifty1 07-15-2011 03:44 AM

http://www.amazon.com/General-Electr.../dp/B00308OUXW

Something along the lines of this? Of course I'll have to find one with the proper rating and all that.

Eighty2Fifty1 07-15-2011 03:45 AM

Quote:

Originally Posted by samc (Post 3087808)
You don't need it, but it's nice to have as a redundant backup if and when you need an alternate brewing set up. For example you suddenly get the urge to come to the dark side and BIAB !

Don't tell anyone, but I'm still an extract brewer:eek:

Eighty2Fifty1 07-15-2011 03:50 AM

Or use the same PID to control both, just like in the thread below this one...

wyzazz 07-15-2011 12:57 PM

You can use a PID with Manual Mode (Like the Auber PID's) that will allow you to set the duty cycle of the element to a percentage or you can use a PWM to control it. Both require an SSR to drive the element with the proper voltage and to be honest when it's all said and done the PID is only around $25.00 more if you build the PWM yourself. The choice is yours.

EarthBound 07-15-2011 02:09 PM

Quote:

Originally Posted by wyzazz (Post 3088448)
You can use a PID with Manual Mode (Like the Auber PID's) that will allow you to set the duty cycle of the element to a percentage or you can use a PWM to control it. Both require an SSR to drive the element with the proper voltage and to be honest when it's all said and done the PID is only around $25.00 more if you build the PWM yourself. The choice is yours.

I agree with this but would like to add that it's always good to have a redundant PID, just IMO.

Walker 07-18-2011 07:32 PM

Quote:

Originally Posted by Eighty2Fifty1 (Post 3087826)
http://www.amazon.com/General-Electr.../dp/B00308OUXW

Something along the lines of this? Of course I'll have to find one with the proper rating and all that.

Those electric range controllers won't work for an electric kettle, even if you find one rated for the amps you need. They don't turn on and off very frequently.

On a stove, this is fine because the heat transfer from hetaing element to cooking pot isn't very efficient. When the element turns off, there is a lot of heat still trapped in the element that will continue to be distributed to the cooking pot.

However, when you have an element actually submersed in the liquid, the heat transfer is extremely efficient. If you tried to use an infinite switch from an electric stove to control your kettle, you would get a pulsating boil; boil for a little while... stop for a little while. repeat.

You want that on/off kind of control, but you need it to happen at a much higher frequency than those knobs will allow.

Bachhus 07-18-2011 08:17 PM

I didn't want to deal with a pid either on my boil kettle. I opted to go the route of a PWM ( pulse width modulator). My reasoning was I could build it, I like doing that sort of thing, I would have a simple dial that took it from off to full power and could easily be dialed back to achieve the desired power without having to change duty cycles on a pid. Walker posted some great info on PWM designs a while back. That's what I used and changed a few things around to have led indicator lights.

My 0.02. Hope it helps


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