Archive for March, 2011

DIY PID Controlled Sous Vide Using a Crockpot

51 Comments »

I recently picked up a copy of Jeff Potter’s excellent book, Cooking for Geeks: Real Science, Great Hacks and Good Food (Amazon Link). In the book, Potter discusses Sous vide cooking, French for “under vacuum”, this is a method of vacuum sealing food and cooking in a temperature controlled water bath for an extended period of time. The effect is that the temperature gradient across sous vide cooked food is small and has an even “doneness” the entire way through.  By carefully selecting the temperature of the water bath, the chemical reactions that take place during cooking can be selected.

Potter presents a DIY method of building your own sous vide cooker with a crock pot and temperature cutoff switch.  This is probably good enough for any use I’d have, but as somebody with a bit of controls background, I felt like I could do better: a PID controller to maintain the water bath temperature.  PID control allows for closed-loop feedback to regulate the temperature to respond to disturbances and minimize control deviations such as setpoint overshoot.

Consumer temperature controlled sous vide units exist, but typically sell for around $500.  I decided to build my own, as my controls engineer friend put it: “you have the rightful indignation of somebody who knows they’re getting ripped off.”

I decided to combine Potter’s approach with my controls knowledge to build the plug and play crock pot PID controller that can control the cooking temperature to within 1°F, which is probably far more precision than is necessary.

Read the rest of this entry »