Arduino Kegerator Temperature Controller

So I have been slowly getting into kegging, and recently got a great deal on a small bar fridge, the Danby one which holds 2 cornies. I find that the factory temperature controller (in mine at least) pretty much sucks, and can't hold a constant temperature. I had a glass of water in it, for checking liquid temperature, and it would vary from 5C to frozen, so I had to do something. I decided to build an Arduino one with mostly stuff I had laying around, so it didn't cost me much. If you had to go from scratch, I would say around $20 probably (ebay prices). Basically, I have a temperature probe in the fridge which is a 'onewire' sensor, super easy to work with. The arduino can be set in 0.5 degree increments, and is currently programmed to keep it within 1 degree of that, and it also has a 5 minute compressor cool-down time programmed in. I built a remote "relay box" which also has the guts from a wall wart transformer, which feeds into the circuit board so that I don't need to have 2 things plugged in. Still need to build a box for the circuit board/LCD, but I am trying to decide what I want to do... might dremel out a cutout in the door for it, or in the bump on top near the front (bad for spillage once I install my taps).
I know the temperature is set kinda high, but I just got it going and want to make sure its accurate before I set it too cold
Let me know what you think!

Nice. I built something like this but with a heater too. I used a Picaxe and a 40amp SSR instead of an arduino and a relay. I made it have an adjustable offset so there is a 'dead band' in there. That way you can run temps right where you want them sometimes, but other times when its less important you can let the temp come up 2 or 3 extra degrees before cooling again to help stop your compressor from short cycling.

Ya, I was thinking about making it adjustable, but didn't bother. I actually dont have buttons or anything for adjusting the temperature, since I dont know how I'm going to mount it... I'm just shorting pins right now to adjust it . I'm hoping it doesn't run too frequently at 1 degree, I might have to adjust that if so. Just realized when I went down to pour a pint, as soon as I open the door the temp jumps up (the sensor is too quick). Might need to put a trigger delay in...

I checked my ebay history, and here's what I paid for some of the stuff (approx).

LCD: $3
Relay: $3.75
Temp Sensor: $1
Atmega 328: $4
LM7805: $0.30
Proto Board: $0.20
Resitors/Caps: $0.50?
Wall Wart: Free (everyone has some kicking around...)

Total: $12.75

Yeah its crazy how cheaply you can put this stuff together huh? What I do is either a: use a thermowell or b: tape the sensor probe to my keg then add insulation over that so that I'm more or less measuring the beer temp rather than the air temp.

Ya, I was trying to tape it to the keg, but duct tape wouldnt stick to the cold metal, and I was too lazy to get an elastic or something. Tomorrow I guess.

Ya, I build stupid little electronic "things" pretty frequently, it's so cheap, and much more fun than buying something. Only problem is I don't document anything, and then later when it's not working right I can't remember what I did in the first place, and end up repurposing the parts or something.

I know the feeling. I now keep a little composition book with little drawings, snippets of code and the like. It makes life way easier. I even standardized things like temp probes so they all have the same plug, etc. It's nice.

can you please share the schematic and the arduino code for this ? is also possible to make this capable to hold the temperature up to 350 degree in celcius ? I have a fairly good Thermistor 100K . I was thinking to build this as a solder heater / station.

Thanks in advance

delokaver said:

can you please share the schematic and the arduino code for this ? is also possible to make this capable to hold the temperature up to 350 degree in celcius ? I have a fairly good Thermistor 100K . I was thinking to build this as a solder heater / station.

Thanks in advance

Click to expand...

this.

I too have been working on a controller for a kegerator. If you would share your code it would be much appreciated. I am interested in seeing how you set up the 5 min cool down interval.

Id also be keen to see the code.
I've been logging temps with an arduino and raspberry pi, and want to use it to control the fridge but am a bit concerned about knackering the compressor if I get it wrong.