I’ll have to check. Planning to do acrylic bottom, three layers of wood, and an acrylic top. Should be awesome.
Hey, I’m new here. I just saw the Photon and thought it would make an interesting platform for my beaglebone project.
I see you guys are well on your way but I’m willing ot help out. I have some insight into what I didn’t like along the way
with my design and why I changed it.
Jeff
welcome!
feel free to share some of your experience. i think with the release of the photon, there is a commerically viable product hiding in this…or at least tindie worthy
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I suggest the use of an alphanumeric display because it allows more information to be conveyed. Having a line saying something like;
Pit Probe: 222/225
Meaning the pit is at 222 with a set point of 225 is very useful. You can have multiple lines for the
4 different probe inputs and you can also add a symbol to display fan on/off or just display fan speed.There are many cheap I2C displays. As mentioned earlier OLEDs are very crisp and low power if a bit small. But a 16x2 or 20x4 LCD would work very nicely.
- Form factor. I find it easier to use an off the shelf case and the dimension the board to fit inside.
Many cases today have clear covers so no holes are needed for the display. Something similiar to this:
http://www.digikey.com/product-search/en?KeyWords=SRW032-CA-ND&WT.z_header=search_go
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Power. I think you’re on the right track with power. For those who need battery power I suggest using one of those car battery jumper boxes with a cigarette lighter type power cord/adapter. This setup is pretty common on the BBQ circuit.
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Calibration. I suggest measuring the values of the voltage divider resistors (R1-R4) before circuit assembly and then using those values in the Steinhart equation. If you want to get really fancy add an I2C eeprom to store those values.
hey @coolnewt have you been using your product much? i am gonna hook up the smoker for a pastrami recipe, and wanted to see if whats in github is the newest code.
very excited!
Hi @avidan, github has the latest code. The up/down buttons will set the temperature alarm. As currently coded there is no audible alarm based on the set temp but the 4th probe port alarm is hard coded to be the target temperature for PID output on the 2nd fan port.
There is still something not right with the Steinhart constants I believe. Maybe it is my probes, but you will know immediately by hooking one up and seeing if it reads room temp and a “hot” temp correctly. If you could try that test w/ your probes that would help me in narrowing down the issue. If you measure and update your reference voltage, that may also help. See here.
ya. its showing room temps as 86 degrees.
i dont remember if the probe is an et-732 or an et-73
i think they have different variables…
have you had a chance to look at the constants on the heatermeter project? they use the same probes.
These probes contain NTC thermistors. The best way to get Steinhart constants is to look at the Resistance Vs Temperature chart of the sensor and calculate the constants using only the temperature range of interest.
If I recall the ET-73 is a 204CT-4 thermistor.
I forgot to add another easy test is to measure the resistance of the probe and then compare that to the resistance calculated from the voltage measurement.
Just wondering where you guys got you PCB done? I’m looking to make one of these so it’s ready before spring.
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I've tried using the heatermeter ones and something one off still.
I'll look into this. This is the closest to a datasheet for the probes I've gotten!
@greatwitenorth, I went through OSH Park.
@coolnewt I’m wondering whats the purpose of the 1K resistor in series between the probe and the input pin on the spark? Is it necessary?
@greatwitenorth I don't think it is necessary, but it was suggested by BDub to act as a low pass filter.
2.It might be a good idea to do a Low Pass RC filter with the inputs in a different way so that you have a resistor always in series with the analog input. A 1k and 1uF should be plenty fast for temperature sensors. Then you still have your 10k pull up and thermistor pulldown on the front end. Assuming the impedance of the ADC input is high, you won't get much of a voltage divider effect when taking a sample. The large 1uF cap will also help this along, effectively lowering your input impedance.
Just wanted to let everyone here know that I’ve been working on a mobile app for the smartBBQ. I’ve had to tweak the firmware a bit to output events. But it should still work with the circuit board that’s been created (I hope to get one printed out soon).
Here’s the github url for the app:
github url for the updated firmware:
The app is very basic at the moment:
- Login to your spark core account
- Select a core that is running the smartBBQ firmware
- Get the temperature of probe on A3
- Logout
So there’s still quite a bit of work to do. Any suggestions are greatly appreciated. Here’s a few ideas that I’d like to include in the app:
- select probe
- Probe calibration
- Alarm ring (while in the app and via push notifications)
- Graph of probe temp over time
- Visual of when the fan is running (spinning fan icon)
Also I’m thinking that I’ll make the assumption that J1 and J2 are for BBQ 1. J1 is the meat and J2 is the BBQ internal temp. And the same applies for J3 and J4. This will make the app interface a bit easier to develop.
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This is super awesome @greatwitenorth! It would be awesome to see a video demo of the app/BBQ in action!
Also, just a thought…I wonder what percentage of grills are in range of wifi, as most are in backyards, on rooftops, etc. This might be an awesome project to test out the Electron with when it’s released to ensure all grills would be connected without fail.
i agree. super awesome. excited for summer.
hi guys, wondering how this project is going. Did it work? Overheating issues resolved?
Wondering if I should order the PCB schematic on the github repo, or if there are further tips?
hi mterril, the voltage regulator does not overheat to failure, but it gets hot enough that it should be replaced with a switching regulator. I haven’t looked for one yet, but you can likely find one w/ the same package for a drop in replacement. I have not been able to get the accuracy out of the probes that others have. It seems to be a f/w issue though. @jlbeck thought the ET-73 uses a 204CT-4 thermistor. I haven’t explored this yet, but doing so may reveal more accurate Steinhart constants.
Hey guys, just stumbled upon this project. I have been working on something similar by myself. I have been working on a smoker controller for an electric grill. I have had some trouble getting my thermometer to display the right temperature (My circuit design skills are fairly weak, while my coding experience is stronger). So hopefully after looking through your design I can help mine.
On my controller I have a small 1" OLED display that shows the temperature, and in the future I hope to put an interface for setting the temp/ other options. Currently temp is controlled through a webapp that uses parse.
I will make a thread on my controller once I get further along. My progress has been hindered by college and job searching. Just about to graduate!
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