SeattleMatt
Well-Known Member
Thought I would share an experience with a lesson learned (keep it simple stupid).
Alright, I decided to build a fermentation chamber from an old cube fridge and some foam board insulation... a lot like everyone else's. I took the easy/less attractive route with the actual chamber but went overboard with the thermostat.
I bought some 1.5" thick foam (qty 2, 2'x8'), a piece of plywood, some casters, liquid nails, and expanding (crack filler) insulation.
First, I put the casters on the plywood (cut to 3'x2'). I then took the feet and door off the fridge and screwed it to the plywood. Next, I cut and glued (liquid nails) the foam to the fridge and base. I left the door unglued of course... it's just tight fitting.
That was the easy part. Here's the fun stuff.
I'm an electrical engineer so what do I do? I build a temperature controller from the ground up.
I started with a microcontroller development board with a 72MHz ARM processor. It's a FEZ Panda with the .NET micro framework. I bought three thermistors to measure my temperatures and three adjustable current sources so that I could calculate my temps using the analog input ports on the microcontroller. I used the Steinhart Hart equation to calculate my temps. The only complication was, I had to find an approximation for the natural log, and the square root (for arithmetic geometric mean)... Google and Wikipedia were really helpful.
I am controlling three 120Vac outlets that I plug the fridge, 200W space heater and a fan into.
So my controller measures three temperatures (Beer Temp, Ferm Chamber Temp, and Garage Temp). It does this once a second and makes a decision based on the average of the last 10 seconds. It displays all three temps and the current set point on the LCD.
So after all that time designing, building and programming, my recommendation is... Keep It Simple Stupid.
Although, I do have the ability to log my temperatures to a usb flash drive, or possibly monitor temps from my iPhone but that would take a lot more time.
Alright, I decided to build a fermentation chamber from an old cube fridge and some foam board insulation... a lot like everyone else's. I took the easy/less attractive route with the actual chamber but went overboard with the thermostat.
I bought some 1.5" thick foam (qty 2, 2'x8'), a piece of plywood, some casters, liquid nails, and expanding (crack filler) insulation.
First, I put the casters on the plywood (cut to 3'x2'). I then took the feet and door off the fridge and screwed it to the plywood. Next, I cut and glued (liquid nails) the foam to the fridge and base. I left the door unglued of course... it's just tight fitting.
That was the easy part. Here's the fun stuff.
I'm an electrical engineer so what do I do? I build a temperature controller from the ground up.
I started with a microcontroller development board with a 72MHz ARM processor. It's a FEZ Panda with the .NET micro framework. I bought three thermistors to measure my temperatures and three adjustable current sources so that I could calculate my temps using the analog input ports on the microcontroller. I used the Steinhart Hart equation to calculate my temps. The only complication was, I had to find an approximation for the natural log, and the square root (for arithmetic geometric mean)... Google and Wikipedia were really helpful.
I am controlling three 120Vac outlets that I plug the fridge, 200W space heater and a fan into.
So my controller measures three temperatures (Beer Temp, Ferm Chamber Temp, and Garage Temp). It does this once a second and makes a decision based on the average of the last 10 seconds. It displays all three temps and the current set point on the LCD.
So after all that time designing, building and programming, my recommendation is... Keep It Simple Stupid.
Although, I do have the ability to log my temperatures to a usb flash drive, or possibly monitor temps from my iPhone but that would take a lot more time.
