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Sensors, Actuators, and Robotics » Temp probe needed for BBQ draft control

June 24, 2010
by Solorbob
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I'm wanting to build a draft control system for my BBQ smoker. The basic mechanics is when the temp falls below a certain point, the MCU turns on a fan to stoke up the charcoal. The fan goes off after a fixed time or if the temp rises to a pre-programmed temp.

I thought about using the same type of thing as in the instructional video, but I figured I should be able to get a food safe/cooking safe probe to do the same basic thing for a pretty good price.

I've found a few Type K Thermocouples Probes on ebay for around $5-$10.
Here is the one that I'm talking about and same basic idea. I'm not wanting it to probe the meat, but the temp inside the smoker. ebay probe:

http://cgi.ebay.com/1-X-4-Type-K-Thermocouples-Probe-0-400-C-Temp-Sensor-/170466843188?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item27b09d9a34

Will this probe work or does anyone have any suggestions on a good probe to use?

Thanks, Shawn

June 24, 2010
by mongo
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Type K T/C's are widely used in food and many other industries. They are typically more expensive than say the type J but that is because they are more or less stainless steel as opposed to copper and iron.

Thermocouples are typically more difficult to work with as they require some kind of compensator circuit to offset certain properties and maintaining linearity.

Many pre-made circuits are available and there are even commercial temperature controllers that are programmable for a wide variety of sensors from most thermocouples and RTD's.

RTD's are easier to interface and don't require compensating circuitry, as they are basically a resistor that changes value with temperature. Most are in the 100 ohm range. The changes are small so some amplification will be necessary to give enough of a signal range to be useful but it is not a difficult circuit.

I use a Watlow 1/32 DIN panel unit for a similar purpose. It uses the RTD rather than the thermocouples but can be programmed for most types. hey cost anywhere from $25.00 for used but functional, to about $150.00 brand new.

I'll dig it up and post a pic tomorrow, meanwhile, here is a link to the Watlow data sheet. Watlow controller

June 26, 2010
by Solorbob
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thanks

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