Accurate DIY Sous Vide "On the Cheap"

DIY Sous-vide has been around for a while, with the most popular (and cheapest) option being the "Beer Cooler Method". The two main problems with this method are the inability to get at the high temperatures needed to cook vegetable based dishes, and the lack of accurate temperature control needed for more advanced experiments (say with eggs).

I decide to try and build my own cheap, accurate, and simple sous-vide water immersion cooker. The components needed are simple:

• A temperature controller 
• A heating element
• An every-day pot

Since I didn't want to pay 50$ for a pre-built PID temperature controller, I set out to build my own. I used a 10$ immersion heater as a heating element, a NTC thermistor placed into a copper tube with end soldered shut and attached to a simple hysteresis controller.

In order to design the controller circuit, one needs to first characterize the resistance of the NTC for the temperature values that were going to be using.  I designed the circuit to work between thermistor values between 20 and 80 ohms, corresponding to around 45 and 88 degrees Celsius. The actual circuit is displayed below:

The Relay used is a five-volt Arduino relay board, which for 4$ includes the neccesary transistor as well as a handy LED for easy monitoring. The entire circuit fits into a small ex-cellphone box:

Finally - The heater in action, trying to cook some chicken:

Results? we'll soon find out..