DIY: UDS temp controller using Android

Update: I'm back in business. I got my replacement IOIO and repaired the controller. (And yes, I'm adding a diode to prevent me from being an idiot again. Well, I'll still be an idiot but at least I won't have to pay for it.) While waiting for the part to arrive I took the time to update the hardware with a much smaller blower. I'm also fiddling around with the PID settings.

I ran another test today and the new blower/PID settings seemed to help. I'm still having issues with the temperature shooting past the set point at first but then it settles down and holds a pretty steady temperature. Here's the chart from today:

I'm pretty pleased with those results (green line is blower speed, flat blue line is target temperature, other two lines are the thermometers). Clearly the blower kicked in when the temp dropped to target and kept it steady. Now I just need to replicate it.

On the downside, the range is still not good. I tried using a different bluetooth dongle and it does have a longer range but the connection is flaky and will cut out for no apparent reason. I will continue to look into that.

SmokinJohn said:

If you would like, I will help you. I have an Arduino, a buttload of resistors, some iGrill probes, a DS18B20, AND a UDS.

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Thanks SmokinJohn. What I plan on doing is writing up the plans at Instructables.com and get feedback from any of you who try to build it. Just so you know, I'm not using an Arduino but something called a IOIO.

Neonnblack said:

Because its fun to make it yourself.

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Exactly!

jcm2m9 said:

You are making nice work. What was the time frame of the chart above. How much did the temp increase when the blower kicked on at the end?

Have you tried running it for several hours?

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Funny you should ask. I ran another test last night for a total of ~4:30. It took ~30 minutes to get up to temperature and then ran for ~4 hours at the target temp. Here's the results; I'm quite happy with it:

The red line is the pit temperature and the one the controller is using to monitor the UDS. As you can see it keeps a very steady temperature other than a 8-degree dip early on. I'll guess most kitchen ovens aren't more accurate than that.

I still haven't tested with food in the smoker so that will be next. I need to add the grills first, which I hope to have done by this weekend.

I'll start putting together the Instructables.com page with some pictures and the parts I used. The thing that will take me the longest is creating a circuit diagram.

tx_hellraiser said:

Deeg what are you using to make your andriod app?

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Are you talking about the software? I'm writing it in Java 6 in Eclipse using the Android plugin. The DB is sqlite and the charting software is AChartEngine. Does that answer your question?

I've put up some pictures and started a list of the parts. Once that's done I'll start filling in with directions. You'll need some patience with me: I can code with anybody but my prose is awful and often ambiguous. I will listen to any and all constructive criticism or anything you think will make the step-by-step directions easier to follow.

http://www.instructables.com/id/E5X914VH7UR7LEK/

The Instructable page is private (meaning it hasn't been published yet) which means you can only get there if you know the URL above. Once we've ironed out most of the problems I'll publish it. Thanks all!

I've updated the instructions with a list of all the parts, links, and prices.

I ran a test last weekend with real food. The controller performed well enough--the only problem was that it lost the connection with the Android twice during a ten-hour cook. I'll have to put in keep-alive logic at some point.

I'm in the process of writing up a schematic. This will take a little time because I have to learn KiCad on the fly. I also need to figure out the best way for you to install the app on your phones. I don't know what the process is for getting an app added to the Google store or if there's another way.

I'm on vacation for the next two weeks so there won't be much until after then.

I updated the instructions with a minimal how-to for installing the app. Somebody give it a try and let me know if it works.

http://www.instructables.com/id/E5X914VH7UR7LEK/?ALLSTEPS

I'll try to have the schematic done in a week or two but no promises. What I'll probably end up doing is adding a draft schematic and having people take a look to see if they notice any errors.

The parts listed on the Instructables page is pretty much the ones I would (and did) use. The only differences are listed on the page:
1) I'd use different mono jacks, only because they'd be easier to solder.
2) I'm still looking for a satisfactory Bluetooth dongle. The ones I've been using have a short range(20-30 ft). Until this gets ironed out you may have to buy more than one. Most of them have been cheap (< $10), which may be why I'm having problems.

I've updated the instructions with a draft schematic. I'm still learning Kicad and haven't figured out how to export the schematic as an image so it's just a screenshot for now. Depending on where you bought the audio jacks the pin numbers for the jacks might not match the pins on the schematic so keep an eye out for that.

I'm back from vacation and I'll start updating the page with step-by-step instructions. If there's anything I can add that would make it easier to understand let me know.

http://www.instructables.com/id/E5X914VH7UR7LEK/?ALLSTEPS

I've updated the instructions with a better schematic (I switched to using Fritzing). I've also started filling in the steps with verbiage.

http://www.instructables.com/id/E5X914VH7UR7LEK/?ALLSTEPS

Ran another test today--I smoked 4 racks of ribs on my UDS with the controller. (Which I'm calling the UDS Digital Supervisor, or UDS. Yeah, bad joke.) The supervisor worked very well; here's the chart:

What you might notice is that ~40 minutes into the cook the pit temperature (red line) plummeted 50 degrees. I freaked out at the time but I think what happened was that the wind changed and was blowing away the heat on the top rack (which is near the seal between the top of the drum and the lid). The thermometer on the bottom rack (light-blue line) didn't drop and then went up as the fan kicked in. It wasn't until 12:00 that I figured this out and put up a wind screen next to the smoker--you can see the two thermometers begin to converge after that.

The supervisor kept the pit temp very near the target temp for over 6 hours. The craziness at the end is when I opened the smoker to pull out the ribs but forgot to turn off the supervisor.

Update: This is largely about the software. I've added the functionality to set off an alarm if a thermometer registers a temperature outside a range. I probably went a bit overboard but the app can now tweet its status on Twitter. This allows you to follow the status from anywhere and it is easier than setting up a web server. You can follow my smoker at https://twitter.com/deegsmoker

Made some updates to the monitor screen. Everything is documented on the Instructables page: http://www.instructables.com/id/E5X914VH7UR7LEK/?ALLSTEPS

The instructables page is pretty much done and I expect all changes/updates to be in just the app. I've used the Supervisor multiple times in the last month and the only major problem I'm having is that the Bluetooth connection goes down at times. The creator of the IOIO says it's because my Bluetooth dongle isn't entire compatible with my phone so I'm experimenting with more dongles.