Thursday, September 4, 2014

cheapest U$5.97 DIY sous vide setup

Yours truly is no stranger to DIY sous vide setup, having dabble in various microncontroller based home made sous vide setup. The PID controlled arduino sous vide setup by yours truly can be found here This PID controlled arduino sous vide has been instrumental in setting up for the perfect dinner dates with the missus. I have cooked fabulous steaks, short ribs, lamb racks, and the epitome of my DIY sous vide home cooking: the effortless Beef Rendang. Details of the beef rendang can be found here

After rubbing shoulders with humans at several maker faire, or maker inspired activities across the continents spanning many miles apart
humans often remarked: "it looks so complicated/dangerous/scary!", "I want to have one but I can't write the program/wire the electrical/solder the electronics", " i want to buy a commercial one/the parts/components, but it is out of my reach", etc.

After seeing a fellow foodie and sous vide enthusiast trying to justify to own a sous vide setup; considerations include the cost, the complexity of setting up, the safety. Perhaps there might be something I can help to bridge this money/time/technological gap. Note: sous vide campaigns on kickstarter is tempting, but the waiting time for delivery is causing him anxiety.

After some searching online for cheap alternatives, I came across this temperature controller from aliexpress that cost U$5.97 with free shipping (to Singapore, that is). It sports an 8bit 32pin MCU the STM8S103K

On the aliexpress product page, nothing was written about the control theory used to ensure the settling time, the rise time w.r.t to the target temperature. This module also sports a relay that is capable of 10A to be used to control a heating apparatus. The other nice thing is, it fits in a regular name card holder. Nonetheless, the entry price is low enough to tempt me to click "BUY". There is a caveat, the manual that comes in the package is in chinese.

parts needed
1. U$5.97 temperature controller module from "middle kingdom"
2. a modified single face plate AC socket & plug (UK standard socket and plug)
3. a heating vessel

instruments needed
1. digital thermometer
2. Fluke wireless thermometer is optional

prep the U$5.97 temperature controller. The exposed AC end that is very close to the LHS push button has to be insulated. I have used some hot glue, and also a casing to isolate from human touching the PCB connectors accidentally. Thus module comes with screw terminals as connector for the DC supply and AC load. Solder a DC connector to the supply side. For the AC load side, I have used 2 wires, one end is cript with a fork cable lug, the other end is tinned, and to be connected to a screw down terminal block.

modified AC socket & plug (UK standard socket and plug). This step can be potentially hazardous if safety procedures are not observed. Do NOT work on an electrical AC socket while it is plug into a live source. Make sure the exposed leads are properly insulated. Wear proper foot wear that comes with rubber sole. Check the working environment has an ELCB tested to be functional. Do NOT use thin wires for AC load. Use the wire from a standard 3 core power cable.

Wire a standard single face plate AC socket & plug as if it is going to be used as an extension. Now, instead of the live wire (brown colour, UK standard) going directly to the socket pin where it is supposed to be; make an "open circuit" on the live wire and connect the exposed ends to the screw down terminal block. This terminal block will act as a "switch" to be controlled by the relay on the temperature controller module.

Please note this might not be the best way of doing it with the wires exposed. If you have a better way of connecting a relay to an AC live wire, give me a shoutout.

step 3
prep a heating vessel. I have used a cheapo 1.3L mini heater jug cum cooker as my heating vessel. It comes with an adjustable knob for the heat setting and is rated as 1100w (max) on the box.

connect all the components together. before turning it on, perform a final check for correct wiring, proper insulation, AC safety standard, etc.

perform intial heating/temperature test. make sure the temperature register by the sensor of the temperature controller module is approximately to the digital thermometer.

test cook an 64degC 45min egg.