As I was upgrading my 3D printer, I wanted to use an alternative heated platform. This new heated platform is a rubber silicone heating pad. You can take this pad, plug it straight into the wall outlet and it will eventually heat up to over 400 degrees Fahrenheit. The issue is you want to limit the temperature to the heated platform to around 200 degrees Fahrenheit. The way you limit the platform temperature is put the pad on a relay, attach a temperature sensor to the bottom of the pad, then program a micro-controller that reads the temperature sensor and toggles the relay off and on to maintain the proper temperature.

To prototype this design out I decided to create a device that is similar. I took my crock-pot and  converted it a sous-vide cooker.

So what is a sous-vide cooker? Well if you ask Wikipedia she says:

Sous-vide (/suːˈviːd/; French for “under vacuum”)^[1] is a method of cooking in which food is sealed in airtight plastic bags then placed in a water bath or in a temperature-controlled steam environment for longer than normal cooking times—96 hours or more, in some cases—at an accurately regulated temperature much lower than normally used for cooking, typically around 55 to 60 °C (131 to 140 °F) for meat and higher for vegetables. The intent is to cook the item evenly, ensuring that the inside is properly cooked without overcooking the outside, and retain moisture.

So generally the crock-pot maintains the water bath. The long black cable in the first picture is the temperature sensor.  The wood box is a variant of my box generator script. I configured the box to hold the crock-pot up front and electronics in the back so it is an all-in-one device that I can easily move it about.

I cut an opening in the front so I can still access the off-low-high switch.

The original code came from Adafuit, but I added my own controls with the three way switch and two knobs.

Position one with the switch means device is on and the grey heat knob sets the water bath temperature.  Position two lets me set a count down clock in minuets with the black knob. Position three will start the clock to the count down. When it hits zero, the device will turn on to the temperature set by the grey knob.

The purpose of the countdown lets me take out a frozen bag of food, place it in the water bath to defrost before I go into work in the morning. Lets say I set the count down to four or six hours. The sous-vide turns on and it is ready when I get home. Or if I am late or something I won’t be able to over cook the food too far because it will only go to the preset temperature.

Here is a picture of the guts in the back:

Here is the arduino with the seeed studio relay shield.

Here is the standard 120V double wall outlet. The left side is triggered by the relay shield. So that is where the crock-pot is plugged into. The right side is always on. In this case a 5V transform to run the arduino.

The device works great. I can still retro use it as a crock-pot by just leaving the black temperature sensor out. The other thing I got out of this project is working with a PID controller. A PID controller is required to better maintain the heated bed of the 3D printer.