FreezerControl
Project Freezer
problem:
orginal regulator on freezer became faulty, It was made very simple with a Capliar tube. The tube became leaky for an unknown reason, thus removing the capliar effect. This cause the freezer to run until the thermal protection inside the compressor desided it was time to switch off. This happens after the freezer reaches the limit for the coolant used, making the freezer go down to just a bit below -30c. As this is not optimal in regards to electrical bill, somthing had to be done. And was did, 1-2 years later...
solution:
There were several options. 1. buy a new capilar tube w/switch.
2. buy a electrical regulation
3. build from the ground and up, an electrical regulation
Option 1: have the fault that I do not like mekanical solutions.
Option 2: costly, about 50Euro or so.
Option 3: more cheep, only components were the expense.
I did some research on this, main problem was finding a relay I could trust to make and break the highly inductive load of the compressor. I do not fancy sparks flying around and risk the relay melt down and set a fire :-)
After talking with a expert on household equipment at work, he gave me a ready-to-use control with a potmeter, relay, sensor electronics and 2 sensors. Only downside was there was no documentation to find on it nor did he have any :-(
I found that by only attaching one sensor to it, it would switch the compressor on at around +5c and off again around +4.6c. I had a el-cheep-o indoor/outdoor sensor wraped in tinfoil closely to the controlers sensor. the now spare sensor was too wraped into this, and I measured the resistance.
The sensors seams to be a 5Kohm NTC sensor type. NTC I am sure of, resistance rises with lower temp :) and it was about 5Kohm at 23c, the 5Kohm is the rated resistance at 25c.
After a quick and dirty calculation, I found that about 18-20K resistance in // with the sensor, would lead the controler to think that there was only +5C in the freezer, where as the actual temp. would be -18c.
A 18K resistor was soldered onto the controler's sensor input, fantastic, the compressor run untill -18.5c, switched off, switched back on at -17.4c. Perfect!
This worked for a couple of cycles, I compaired myself with GOD, no other, and ate some late supper. Now, the regulation seams off again... el-cheep-o sensor says -8c and compressor is not running...
How depressing...
A solution must be found... and pictures uploaded :)
--Jan Goofy 19:23, 11 July 2009 (UTC)
