Problem: As a result of a Power outage, an electrical power surge took out my deep freezer. It was full and melting quickly.
Analysis: I found that the cooling system still worked, it just was not being regulated by the thermostat anymore. If I turned the dial to cold it would turn on, and if I turned it warmer it would turn off, but it would not cycle on/off automatically to maintain the proper temperature. It's a Norge-Warner 15 cu.ft. unit from the 50's that I am sure I cannot get parts for.
Solution: I turned the control to cold and then built a simple relay outlet that can turn power to the unit on for 40 minutes, then off for 20 minutes to let the cooling system keep from over heating. Then it repeats.
Components: I used a $3.40 Arduino Nano V3.0 compatible, a relay from out of a WeiKedz Starter Kit, an 89 cent 110 volt ac outlet from Jameco that I bought on a clearance sale, a power cord that I cut off of an old copier that was junk, a $1 USB power supply, a spare USB cable, four short pieces of scrap wire, some solder, some heat shrink tubing, and a used plastic container from the recycle bin.
Assembly: I connected the relay coil to ground and digital pin 4 of the Nano.
I connected the neutral and ground wires of the power cord directly to the ac outlet and connected the hot lead to the common post of the relay.
I then connected the normal open post of the relay to the hot connection of the ac outlet.
I wrote and downloaded a simple program that initializes the output D4 then repeats the loop of turning the output on, wait for 40 minutes, turn the output off, and wait for 20 minutes.
I put it all in the plastic container and clipped the ac outlet into a hole in the side of the container.
I glued the Nano to the side of the container so the USB cord could connect from the outside of the container and glued the power cord to the container where it entered through a round hole.
I plugged the freezer into the ac outlet on the side of my plastic container, plugged the power cord and USB power supply into a surge suppressed outlet strip and plugged the outlet strip into the ac wall outlet.
I connected the USB cord to the Nano and USB power supply and it came to life.
Result: It has been working fine ever since. The contents are staying cold and the cooling unit is not overheating.
This project took about an hour and a half and less than $10 in parts to complete.