When we visited my parents last summer, they were talking about the idea of having a pool thermometer that they could read from inside. There are various options on the market already but none of them met their criteria. I went home thinking this could be an interesting project and Christmas gift.
While I’ve done electronics projects before, I feel like very much of a newbie and there was a ton of learning involved in the project. My first challenge was learning how to read temperatures with a sensor that would be submerged all the time. Some research led me to the DS18B20 waterproof temperature sensor and I found a nice tutorial about using it with Arduino. I bought a couple official ones from Adafruit even though there are cheaper versions on Amazon. I only needed one for the project but I figured there was a good potential for me to screw one up. I had some ESP8266 boards left over from the LED panel project and that seemed like a good fit for this project. The boards are only a couple bucks and they have WiFi built in. With a little breadboard action, I was able to see the temperatures from the debugging output of the board.
The next step was to somehow publish that data. There are endless options, but to keep things simple, I started with Adafruit IO. It’s free for the small amount of data that I’d be sending and there were good tutorials about using it with the ESP8266 boards. That was quite simple to set up and before I knew it, I had a temperature sensor that sent data to a website!
I was going to explore ordering a custom breadboard and I did start down that path but I got a bit overwhelmed trying to find all my specific parts in the tool. My circuit wasn’t very complicated, so I ended up just using some perf board and manually soldering the components in place.
I wanted to make it easy to replace all the individual components so I ended up using connectors in quite a few places. I put a headphone jack on the end of the temperature probe and it plugs into a jack in the box. Then the box jack has another wire that plugs into the board.
Before I could figure out the box situation, I needed to figure out how to get power to it and that ended up taking me a lot of time. I landed on a power socket that’s meant for RVs connected to a buck converter to bring the 120v down to 5v. It was bulky but I made it easier by removing the long cable and plug on the power socket.
That just left the box and for that I opened up Fusion 360 to make a custom box that I would 3D print. It had all the holes in just the right places, the lid fits snugly, and all the screws are countersunk. The only problem was that the standoffs I built in for the ESP8266 were too tall/thin and they broke but ultimately it’s not a big deal.
I was nervous about whether the WiFi signal would reach from their pool, but thankfully they don’t have any competing WiFi traffic in the area and it worked fine! I got Dad set up with the development environment so he could make changes to the code, and he had an idea to make the probe wire much longer and keep the box in the pool house. There are endless possibilities since I’ve basically handed him a prototype and walked away, but hopefully it will work at least for a little while! I’m expecting it to take a couple more iterations to work through bugs and maybe we’ll build nicer software for it, but at this point, I’m kind of amazed that it actually worked.