Other than the lack of a real enclosure, I'm pretty satisfied with QPID at this point. It does everything I originally wanted it do, and it makes hours and hours of smoking at a precise temperature an easy, hassle free activity. Perhaps it's time to take things to a whole new level...
One of the longest-running debates in the history of food is the correct smoker temperature to use. Some people go with 225 for ribs, others say 250, while some think 200 is best. I think it's time for a little science and technology to turn this debate on its head.
I came across this very interesting (and very technical) article about sous vide cooking, which is French for 'in a vacuum'. The food is sealed in plastic in a vacuum and then slowly cooked in a water bath at a low temperature for a long period of time (sound familiar?). The article does a great job of explaining how heat affects the meat and why holding a lower temperature results in a more tender meat. The key to the whole process is keeping the temperature of the food within a precise temperature range... something that QPID could potentially do!
Sous vide employs water baths to heat the food; the higher specific heat of water allows for rapid heating of the food, and the food temperature will then mirror that of the water bath so maintaining the temperature is quite easy. I'm not about to dunk ribs in a vat of hot water, but I think the way in which the water heats the food can be approximated with some clever software.
Instead of setting the temperature of the smoker, QPID could be configured to quickly reach and hold a specific meat temperature. So perhaps the smoker would start out at 225 initially, but would then scale back to a lower temperature to keep the meat at just the right point. The hardware is already there to do this, all that's required is a little programming.
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I am building pretty much the exact same system and came across your blog via the WiShield forum.
ReplyDeleteI previously built a controller based on an ATMega32 and thermocouples (see http://hruska.us/tempmon/ )
I wanted to take it to the next step and add WiFi so the arduino/WiShield combo was a no-brainer decision.
Do you have any plans to release source code or schematics for other tinkerers? I am most interested in the thermistor table you got from Maverick, since I have one of those lying around as well and I might give up on the thermocouples.
Yes, I am planning on posting the source on GitHub once I've had a chance to clean things up a bit (give me a week or so). As for the schematics, I don't have anything drawn (it's all in my head), but I can post the PCB artwork.
ReplyDeleteI was able to get the datasheet from Maverick for the thermister probes and have that code working great. Not using thermocouples really keeps the cost down and makes the design a lot simpler.
ReplyDeleteFor your 2.5mm plugs, did you have to do anything special due to the extended length of the barrels on the probe jacks? All the plugs I have end up connecting both contacts to the ring of the plug.
Also, I was looking at your graphs - did you abandon PWM to the fan?
Cool, glad Maverick was able to help you out too. The plugs are little long, just slip a small rubber o-ring on and it'll fit fine.
ReplyDeleteI am still using PWM, but due to the limited temperature resolution and high gain factor, the fan speed tends to spend a lot of time at 100% or 0%. But I have also noticed it running at an intermediate level quite often (it's not easily noticeable on the graph).