Adding Temperature Control to an On/Off Crock-Pot

However, after a while the Crock-Pot began to burn the cheese!

After further inspection, we found that this particular Crock-Pot had no native temperature controls, so we decided we would make our own!

Here at Circuit Specialists, we are a huge proponent of the infinitely functional variac device. We figured this would be a perfect match for our on/off only Crock-Pot. This SCR151-NP 1.5 quart model is rated for about 215 degrees.

The theory behind this experiment is that by using a variable auto-transformer (variac), we could run the Crock-Pot at a consistent lower temperature, and not burn any of the delicious cheese dip.

To run this experiment, we are going to use a few tools from our stash of advanced consumer electronics. Featured today will be the:

• Variac TDGC2-0.5 - Open box return, Still fully functional. (See TDGC3-0.5 for the updated model!)
• Mastech MS8340A Multimeter
• Mooshimeter Data-Logging Multimeter
• 2x Thermocouple Adapters
• 2x K-Type Probes
• 1.5 Quart Crock-Pot - SCR151-NP

To set this up, we need to get the Crock-Pot hot enough to burn the cheese. We will use the Mastech Multimeter, coupled with the Mooshimeter Data-Logging Multimeter to record and log our temperature changes. The Mastech provides a clear Fahrenheit temperature readout, but the mooshimeter responds only to voltage and does not have a true probe 'temperature' reading. We are using the Mooshimeter to graph the data to be interpreted later.

After about an hour, we reached 210 degrees Fahrenheit, which was plenty of heat to totally toast the bottom layer. We decided to not let it cross the boiling threshold due to our lid not being completely secure with the probes.

Now, we plugged the Crock-Pot into the variac and reduced the voltage down from the standard wall outlet voltage of 120v to the 78v mark on our variac. At this point, we wait until it starts to level out.

After about 20 minutes, we were down to about 200 degrees, still declining.  About 40 minutes after that, we managed to get the temperature to level out right around 187-188 degrees Fahrenheit. Notice how the voltage has started rising again (red line on mooshimeter) to maintain its heat range.

Here's a short video to give you the overview of the completed Crock-Pot experiment.

Below are the graphs taken from the Mooshimeter.