In response to a number of requests I've received during the last few months, I've posted full specs for the QPID Shield. This PDF includes PCB artwork, component locations, and a detailed parts list. The design is provided under the terms of the TAPR Noncommercial Hardware License.
If you print the document, make sure the 'no scaling' option is selected to ensure that the PCB artwork is printed exactly to scale. Everything's been double checked for accuracy and completeness, but please post a comment below if you encounter any discrepancies or have any questions.
With a major winter storm approaching Chicago this evening, it's hard to imagine that we'll be smoking meat again in a few short months...
Enjoy!
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Thanks. I can wait to get my Arduino and try this out.
ReplyDeleteThanks Mark....I have a couple of questions for you.
ReplyDeleteI would like to use your code with the Sensor Shield instead of a printed PCB but I am running into a few hangups.
Is the Jumper wire J4 used as a common ground? Which resistors are used for the meat probe and the pit temp?
@Big T.: I'm not familiar with the Sensor Shield, but I can answer questions about the QPID shield and the code.
ReplyDeleteThe smoker probe is on analog pin 2, and the meat probe is on analog pin 3; they are pulled up to +5v via 22k resistors R10 and R9 respectively. The pin assignments are defined in QPID.h so you should be able to easily change them for different hardware if needed.
The jumper just provides a ground connection for the smoker probe connector (I didn't want to run a super thin trace between the pins).
R11 and R12 form a simple voltage divider so that the supply voltage (0-15v)can be measured using the analog inputs (0-5v); this will be useful for battery and/or solar power. R8 just controls the bias current for the fan power transistor.
Hope this helps!
Thanks for the information Mark
ReplyDeleteThe sensor shield is just a board that has buckled connections to access the analog and digital connections for the Arduino board.
What I am finding(even with just plugging directly into the pins on the wishield) is that once I plug in the connections for the pit probe(Analog 2) that the display temperature for both the Pit temp and the meat temp changes even though I have nothing plugged into Analog 3. Any ideas what could be causing this?
Getting the Meat probe working is the last thing I have to do and then I can get this up and running.
Hi Mark...Please disregard my note above...I must have had a short or loose connection. The two probes are within 1 degree of eachother...Thanks very much again for your help and for making this project open source
ReplyDelete@Big T.: Excellent, glad everything's working now! Look forward to hearing about your first smoking... :-)
ReplyDeleteHi Mark....One last question regarding the power transistor. What is the voltage that you are supplying to the fan?
ReplyDeleteI have connected my VIN which is 12V to the collector and connected the Signal with resistor R8 to the Base and the positive connection of the fan to the emitter. While my fan turns on it is only getting about 4.9 volts instead of the 12 it need to run at full speed.
Any ideas what I am doing wrong?
You need to connect the emitter to GND, the collector to the negative supply of the fan, and the positive supply of the fan is connected to VIN. Given how a transistor works, the emitter will always be within about a few hundred millivolts of the base (that junction is essentially a diode), and so the emitter voltage is being limited by the 5V signal.
ReplyDeleteThis should help:
ReplyDeletehttp://datasheetoo.com/wp-content/uploads/2010/01/transistor-switching-circuit.png
Thanks Mark...As you can tell I don't have a background in electronics but I am learning!
ReplyDeleteThanks again.