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Are there any low cost (less than $150) solutions to add temperature control to an electric HLT? My setup is a keg with a 5500W water heater element. I love how quickly it brings 15 gallons to boiling (less than 1hr), but it's a bit of a hassle to get the temperature I want.

I know I probably need to be re-circulating to make the temperature consistent, which I can do, but I'm curious if there are some options. I've looked over the instructions at www.theelectricbrewery.com, which is amazing and wonderful, but the cost for the PID, SSR, heat sink, and temperature probe comes out to about $120 before shipping or tax, and without accounting for misc connector and cable costs, let alone any box to contain it all.

Also, running my boil kettle (exact same setup) at 100% is my only option right now, which requires me to have my large fan running over it to keep from boiling over, and I'm not sure if that'll work once summer rolls around. Will one temperature control setup work for both?

Is anyone else working creatively in this realm?

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up vote 5 down vote accepted

Without knowing your system, I can't give you specifics, but Arduino makes great microcontroller USB I/O boards in the $25 range. You program the board through a USB interface using a language similar to C, so it wouldn't be hard to write a PID control program for temperature. You would need an interface to step the thermocouple voltage up to proper levels for the Arduino inputs, but there are a variety of options for that. (For instance, maxim-ic sells a thermocouple-to-digital converter.)

Then you'll need a way of making the outputs useful to control your system. If you have an electric heater, you could probably generate PWM and use a solid-state relay to boost your power. For gas you'd need a valve with an electronic input - I'm sure something exists on the market.

As a reference point, I once read something about this on wired.

And yes, one Arduino microcontroller could control several separate circuits, so you could monitor your brew kettle, but since it stays at a constant temperature, you'd have to find a creative way to measure the boil water height, and even then, it's a laggy system, so controlling the heat is going to be problematic. Maybe you would be better off controlling the cooling fan instead?

Honestly, once all's said and done, I don't think you'll save a lot over the other option, but if you're interested in the experience of creating your own system, it might be a good alternative.

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I can vouch for the Arduino system... implementing this 'homebrew' controller will require programming, a bit of mathematics, and a bit of electronics knowledge (especially if you want to implement the control system off of the provided arduino board.) –  Wayne Dec 27 '10 at 1:21
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