Home > Brew gear, Tech geeks, Temperature monitoring > Generation 1 Project Completions

Generation 1 Project Completions

20140913_184244As anticipated, my main boards for the temperature monitoring circuit came in from OshPark.com last week. The same night they arrived, I soldered a board together and hooked it up to the LCD screen and other circuit bits – and nothing displayed at all. After swallowing down a brief moment of complete panic, I deduced that I must have somehow messed up the pin 3 wiring in my schematic and PCB. When I reviewed the design, my fears were confirmed. I had tied the resistor to the 5V rail instead of GND, which meant there was basically no current flowing through that PCB pin. I decided to desolder the side incorrectly going to 5V and rather deftly (not really) rigged it into the solder pool for pin 1, which is a GND.

20140913_184330The updated schematic and PCB on my SkyDrive folder is now corrected. I also realized I should add some silk screening for the OneWire buses so it is clear which side is the 5V/Power side and which is GND, so that update is included as well.


20140915_202922One everything was working as expected, I loaded the components into the aluminum project box and mounted it on the wall next to my lagering fridge. I bounded upstairs to connect up the computer and test the Windows application I wrote (shown in the previous post)… and then spent several hours fighting with the Bluetooth. Finally I got the bright idea to go down and try to connect with my phone while standing next to the device – and it worked perfectly. Additional research revealed two key points:

  1. I had used a RN42XV modem, which is only a class 2 device and has maximum ranges of 7-10 meters when unobstructed by subflooring, joists, etc. There is a class 1 version, RN41XV, which has a much more powerful transmitter and greater distance… which is probably what I should have used.
  2. A metal enclosure (like my fancy project box) is apparently a totally AWESOME way to completely dampen the effective range of a lower power Bluetooth transmitter

My short-term solution while waiting for the class 1 to arrive was to run the transmitter outside the project box. It’s ugly – but it works. I can connect and download data to my PC now.

On another front I also basically wrapped up my Android application development. It’s not as sophisticated as the Windows application, but it doesn’t need to be. It performs the basic functions of connecting to the device:

  • listing out the sensor information,
  • allows for the name and frequency values to be updated, and
  • the data files can be downloaded.

For someone who had never written an Android application before, and for whom it had been nearly 18 years since I wrote any Java code (the Comp Sci object-oriented design class senior year I took as an “elective”… and made all the CS majors wonder what the hell a Chemical Engineer was doing in there…) I think it turned out pretty well.




One aspect I don’t have working the way I want is displaying the % complete while downloading – basically the BluetoothSocket hangs the user interface thread while it is downloading and the %s never update until it is over and a “download complete” message pops up… but I’ll get there. I intend on posting that code on my SkyDrive as well when it is cleaned up enough.

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