Author Topic: Making a food warmer PID, considering adding pH tracker  (Read 1682 times)

WisconsinDan

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Making a food warmer PID, considering adding pH tracker
« on: October 25, 2015, 04:32:34 AM »
Inspired by some other people's set-ups I have seen on here I have been working at getting a new rig of my own going. I am thinking of using the Avantco with a hotel steam table pan in a water bath. I have been working in my spare time with a TI MSP430 to basically get a temp sensor to display data to a LCD and send it back to a log on my PC and am waiting on a couple of parts to add a relay.  I am going to basically chop an extension cord in half and wire it all together to control the heating elements and continue writing my software for it all.  My vision is to have 2 different modes, 1 for heating as quickly as possible to get the milk to ripening temperatures, and another with ramp PID control for scalding the curd when I make cheddar.  This is all coming about because I am forgetful.  The cat could meow because it found some runny camembert and I would forget to turn the heat off on my set-up, I've been using a Nesco turkey roaster and simply turning the power on and off in intervals as needed, and next thing you know my temperature shoots up like 2 or 3 degrees F in a minute and I am grumbling about it. Going to set up a fan to help create some convection to help control the temperature a little more and prevent overshoot as well.

Actually sending back time stamped data to my computer has gotten me thinking how cool it would also be to send back pH readings to make pH time curves for my makes as well.  I know a lot of people will say, but people have been making cheese for 1000s of years without pH meters, and I agree it is not really a necessary project, my inner-computer-cheesy-geek-brain is beckoning me.

cowboycheese

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Re: Making a food warmer PID, considering adding pH tracker
« Reply #1 on: December 29, 2015, 05:33:17 AM »
Have you gotten anywhere with your design yet?

WisconsinDan

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Re: Making a food warmer PID, considering adding pH tracker
« Reply #2 on: August 21, 2016, 02:54:17 PM »
I haven't actually been on here for awhile, but figured I may as well update this. I have decided against an inline pH set-up because it would just be too irritating to maintain. Also, I have abandoned the water bath idea instead opting for going the griddle/steam table pan route. Works great for me. I have, however, finished writing some code for what ended up being a PD controller. Frankly the biggest source of error is the fact that my temperature measurement only comes from one place in the vat. Whenever I stir the pot the reading can jump by as much as 4 degrees Fahrenheit. In spite of that, if I remember to stir regularly enough I can hold the temperature steady within 0.5 degrees Fahrenheit which is way better than any bang-bang controller I have ever purchased in the past. I also have a ramp feature I added in for increasing temperature 1 degree every 3 minutes. Again, due to my measurement only coming from a single point it is not always ideal, but judging by the temperature vs. time graphs I have made with the data I collect with my device I see it is still much better than anything I was doing before. I am tempted to add additional temperature probes and use the average temperature in the pot, but who knows when I will get around to that. Right now I am more interested in giving the device wireless to use a terminal to create a better user interface. I won't ever be selling one of these, but if anyone is feeling like a bit of a maker I would be happy to share much of my code.