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Old 05-07-2011, 01:31 PM   #1
goaticus
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Default Looking for some help with an Arduino Keezer

Hey,
New guy here. I noticed in my brew-lurking that there seems to be a lot of programming knowledge around and I was wondering if anyone would be willing to help me get an arduino keezer started. I am just getting started with my Uno, but I need to get me keezer up and going asap and can't wait for my knowledge to catch up to my needs.

Up until now I have been using 3 gal cornies in my Sanyo mini (the one with the freezer). I finally bought some 5's and want to make the switch.

While I only need basic functionality to turn the relay on an off based on readings from a 30K (or other) NTC thermistor, what I would ultimately like is to have UP and DOWN temp adjustment buttons, and the Nokia 3310/5110 as a display screen that says what's on tap. I think there may be a third button that turns on the back light for a given amount of time as well unless I can dual purpose one of the temp buttons. Thank for any help. Cheers,
Jessie

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Old 05-07-2011, 01:59 PM   #2
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On second thought, I think I'd like to try a digital sensor and ditch the thermistor. LM35...?

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Old 05-07-2011, 02:24 PM   #3
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Adafruit sells the TMP36, which is easily interfaced to an analog input. I integrated one into my sprinkler controller, but the temp seemed to be about five degrees (F) high. I compensated for it in Arduino code.

http://www.adafruit.com/index.php?ma...roducts_id=165

ANYWAY, I've subscribed because I eventually want to do the same thing. I have 32 years of programming experience, so if you get stuck I might have a suggestion or two. :-)

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Old 05-07-2011, 02:25 PM   #4
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And welcome aboard, by the way!

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Old 05-07-2011, 02:49 PM   #5
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I've got an arduino based temperature controller that uses a thermistor for temperature control and a SSR to turn the fridge on and off - it would probably work for a keezer too. I keep the temperature between 36 and 40, and also have a LCD display (which can be controlled via a keyboard).

I can post the source somewhere if you want it - I was going to just attach it, but the board seems to limit the extensions of the files that can be posted.

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Old 05-07-2011, 03:12 PM   #6
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I use DS1820 one wire sensors. I've tried a multitude of different temp sensors, including thermocouples, and the DS1820 series have provided the most consistent, accurate, and reasonably simple temperature sensing for an Arduino based controller.

Small tactile switches are easy to interface. There are plenty of tutorials at the Arduino playground.

I recommend starting with a serial LCD before trying to tackle the Nokia display. They are cheap and somewhat easy to use. If you have limited programming knowledge, I fear that you'll be frustrated with the Nokia.

Use a simple control algorithm. You don't need PID or anything fancy. Use a variable (integer or float) to hold your temperature setpoint. Give yourself a temperature differential of 1 to 3 degrees. When the keezer's temperature is greater than setpoint + differential, turn on the relay. When the temperature is less than or equal to the setpoint, turn off the relay.

Include a short cycle timer to prevent the relay from triggering quickly and wearing out the compressor. Set a 5 or 10 minute delay so that the relay cannot be triggered again within the delay period (after the relay is turned off). Use the millis() function to measure time elapsed.

Your control code shouldn't be more than about 30 lines. If you use a DS1820, you'll need to include the OneWire library.

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Old 05-08-2011, 03:46 AM   #7
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I already have the 5110, but could get a regular LCD. Gabe, I'd love to take a look at your code and see if it would be a good starting point. From my reading, it sounds like I need to see if my 7cf Costco/Whirlpool freezer has a compressor heater or not that needs to stay powered.

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