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Old 02-07-2013, 10:49 PM   #1
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Default PWM vs PID for BK

i have committed to a Kal clone using his panel kit and website. I have been reading up on PWMs though for my stir plate, and wonder what the pros and cons are of a simple PWM for boil control vs a PID. They seem simple, is it strictly a cost thing to use a PWM?

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Old 02-08-2013, 02:02 AM   #2
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PWM is the simplest way to control your rate of boil because it's a simple linear control just like your stir plate. And since water boils at a constant temperature regardless of the rate of boil, a PID is useless for controlling your boil. But PIDs have caught on & they seem to have everyone's attention right now.

I'm sure that someone will answer with "but you can set your PID for PWM....." and with some you can. But turning a knob is a far simpler solution for boil control, particularly when your brew is about to boil over.

The boil controller at the end of this Instructables article uses PWM.
http://www.instructables.com/id/Installing-a-water-tank-heating-element-in-a-Polar/?ALLSTEPS

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Old 02-08-2013, 08:55 AM   #3
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You are already using a Auberins SYL-2352 PID if you are doing a Kal system clone. The PID has manual control that can be used to regulate the boil rate. The temp probe for it does not need to be moved either. Plus there is no additional equipment required.

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Old 02-08-2013, 01:52 PM   #4
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Yes, I am already committed to the Auber, and I know from Kal's website that it has a manual mode to work like a PWM, I was just wondering why they aren't used more. It seems a lot of people are using PIDs. My panel will have 3 but really I only need 1 PID on the HLT, a temp readout display on the MLT, and a PMW on the BK.

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Old 02-08-2013, 02:14 PM   #5
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When it comes to the boil the advantage of a PID over PWM is ramping up to the boil temp. With a PID you can set an alarm and see the temp so you dont have to be standing there monitoring it every second to avoid a boil over. Depending on your chilling method it can also be useful to see a temp reading while chilling.

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Old 02-08-2013, 03:06 PM   #6
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If you have the correct type of PID, from what I've read, you can control the boil using a manual mode and you don't have to do any other wiring. With a PWM you have a knob you turn and it turns the element up or down, just like your used to on a stove. And they are cheap to buy or build. So either way is fine.

I'd personally go with a PWM because I've built them before and they are dead simple to build and operate. Plus it's another one or two buttons/knobs on the control panel, and who doesn't love buttons and knobs!?

With PID I think you just set the control to manual and enter a rate and you're done...

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Old 02-09-2013, 12:33 AM   #7
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i went PID over PWM so i could heat water in both my HLT and BK to specific temps at the start of my brew day. the BK water is my mash water, the HLT is the HERMS water and then the sparge water. i just use the PID in manual mode on the BK when i'm ready to boil.

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Old 02-09-2013, 12:43 AM   #8
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Quote:
Originally Posted by slakwhere View Post
i went PID over PWM so i could heat water in both my HLT and BK to specific temps at the start of my brew day. the BK water is my mash water, the HLT is the HERMS water and then the sparge water. i just use the PID in manual mode on the BK when i'm ready to boil.
Bingo.! You do good and that is the best (IMHO) way to do it.

The Auderins PID can do the total job easily.

Just saying...
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