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Need some help


#1

Hi All

I would like some help on designing a controller to control my smoker. I have a FEZ Domino and would like to control two 12v fans and I would like to have 4 temp probes. (2 temp probes for inside of the smoker so I can see the temp in of the smoker and 2 temp probes for the meat) I would like to have LCD for the read out.

Any Suggestions?

Thanks for your help


#2

should all work fine on a Domino.

What are your temperature probes, thermocouples? What temp range do they need to support?

What are you going to control the fans with?

What kind of information do you want to display on the LCD. What kind of LCD are you thinking of using? With a Domino (not a Panda II) you are pretty much limited to a serial display unless you want to use a serial->parallel logic chip.


#3

I new to this type of stuff. For the temp probes what be easy to use for reading the temp. For the lcd would to show a preset temp and the actual temp.


#4

ok, so you don’t have all of this stuff from your arduino days, that you’re moving over to Fez with. OK, that makes sense.

Here’s a few pointers.

Fans. To run a fan, you really need to control it via a “switch” as the Fez itself is not capable of switching 12v nor is it capable of supplying the current needed to drive the fan. So to start, you need an idea of how much switching you need to do - as I have no experience in using a smoker, would you expect to typically switch the fan on for minutes for a time, seconds at a time, or always on but varying the power to speed it up/slow it down? Depending on the answer to that, you probably then need to look at relays or other motor control devices, such as this one: http://www.ghielectronics.com/catalog/product/177. You will need to make sure that the relay or H-bridge you use has enough power to switch the current you need.

Displays: if you don’t have a display at the moment, then consider this one: http://www.ghielectronics.com/catalog/product/208 or similar. This plugs into UEXT so it doesn’t consume pins on your outer headers. The serial LCD http://www.ghielectronics.com/catalog/product/144 is also a good option again because it doesn’t use a lot of IOs to get you output capability, but you do only have 2 lines x 16 characters so you’re going to need to scroll.

You’ll probably want a button input or three so you can adjust your temperature setpoint and display etc. Depending on if you bought the Fez , or your experience with electronics, you could make

Temperature sensors will be the “interesting” part. You need food safe since you said you’re inserting some into the meat. I’d suggest you find information on probes online and then ask back here to find out how to interface it to the Fez.

Forgot to ask about “heat control”. What heat source are you planning on using? Are you expecting to control the heat via the Fez as well? Or are the fans to control the airflow which raises / lowers the temperature by inputting colder ambient air into the system?

I hate pointing to this but here goes. Someone has done some of this work in the A forums. You could use their learnings and research in your endeavours. This is just one such example that came back when i Binged it http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1288631058.

The other thing you need to understand, that will be beyond most of us unless there are others in Fez Land who do this to, is the principles in controlling the temperature. Since you’re trying to do that in software, you’ll need to figure out how to put that into an algorithm. Again researching the code from other folk might help.