Well, the procrastinators in me finally lost, both the “build the temp sensor” procrastinator and the “blog about the build” procrastinator. 🙂
In my last blog on the subject, I had everything prototyped on the Sparkfun Redboard. The only remaining step was to find a suitable enclosure and transfer the prototype to a PCB. That involved buying PCBs from a couple different sources and some trial and error in figuring how to best make it fit. At the time, the plan was to put the sensor in the kitchen, and run it through the window (which would involve drilling a hole in the frame – since they’re new windows, that wasn’t an easy task to convince myself to undertake).
For an enclosure, I decided that the board could remain open to the air and mounted to a wooden picture frame (3×3). I would mount the LEDs to one board, and the electronics to another. I bought a 4×6 board, and cut it into two parts. The part that the LEDs were going to be mounted to was dimensionally critical (3.25″x3.25″)as I wanted it to fit snugly in the opening of the frame. The other was not nearly as critical, as it would just be attached to the back of the frame. By having two separate boards, I was able to complete each separately, checking to make sure things worked before putting it all together. As it turned out, that was a necessary step, as my soldering skills aren’t the greatest. The finished product is shown:
The LEDs (from AdaFruit) came together very nicely. They were easily centered on the board, and longer leads were added to attach to the rest of the unit. Once inserted, a piece of cork was cut to fit snugly inside the frame to hide the board from sight. The green LED is the inside temp (in °F), the blue is the outside – yes, we do not use A/C often.
Once I was sure that was working properly, I started working on the circuitry. I bought a clone Nano for the ‘brains’ of the unit. The circuit is very simple, so in theory transferring it to the board would be simple. It was, for the most part. The most difficult part was getting the soldering right. I think a big part of the problem was that i failed to wash the board before i started, so oils were coating it. That caused problems as the solder wouldn’t flow on some connections. Still, after a little troubleshooting, everything came together. The board was then mounted to the back of the frame by means of a few small brads (I had to drill some holes in the board for the brads to fit). in attaching the external temp probe, I considered plugs, but ended up using screw terminals. Everything is powered by an extra USB cable and adaptor. Here’s the back of the unit:
Running the probe outside was easier than i feared, as the window has a small gap in the upper corner of the inside fo the frame. All I had to do was drill a hole from the outside and fish the wire through. It turned out much better than I feared. Now of only the wire was white instead of black. Oh well.
So all in all, the project was fun. I learned a lot through experimenting on how best to lay out these types of boards. While cost is not competitive with store-bought systems, I have no doubt I could easily troubleshoot any problem I have with the system. Thanks for hanging around as I finished this and if you have any questions, please feel free to comment!