Arduino-Based Solar Heater for My Above Ground Pool Answered
A few weeks ago I grabbed the garden hose to top off the pool and noticed how hot the water was as it came out. (the hose had been lying in the sun). So, I decided to put it to good use. We've been looking at solar heaters for the pool but found the prices prohibitive, and being a DIY'er I decided to build my own. I have 50' of black, tangle-free hose coiled on a 2' by 4' piece of Wolmanized, 3/4" plywood. This is perched on top of an 8' 4by4 post which I sunk into the ground near the pool's filter. To feed the hose I installed a faucet in the filter's return line which is under sufficient pressure to travel up and into the hose. The other end comes down to an electric valve before emptying back into the pool. The Arduino portion of the project consists of an Arduino Uno board, a DS18B20 temperature sensor probe, a 12-volt, 3-amp power supply, A small prototype board that holds two 12-volt relays and two 2N3904 transistors which the Arduino triggers, two 12-volt car-type relays which are triggered by the smaller ones, and a Mallory Sonalert. My idea was to have the Arduino monitor the temperature in the return line from the solar hose coil, and when it reaches 80 degrees F, the Sonalert goes off for 5 seconds to warn swimmers that hot water will be coming out of the return spout in the pool. And after the warning sounds, the electric valve then opens for 2 minutes, flushing the warmed water into the pool. Since the system is driven by the pool's filter, the solar hose is replenished during this flush period, and when the valve closes, that new water is then heated, and the whole process starts over.
The Arduino code consists of a couple libraries to incorporate and read the temp' probe's output, a subroutine which tests both the Sonalert and the valve when the system is first plugged in, and then the necessary code in the Void Loop section which simply waits for the temp' to reach a preset level and then sound the alert and then open the valve.
The system is built into an 8" by 6" electrical box that mounts on the 4 by 4 post just under the solar hose panel.
The systems been up and running for about a week now and I've averaged about a 2 degree rise in the pool's water temp' per day.
If anyone is interested in seeing photos of the project, or the Arduino code, I'll be happy to provide.
UPDATE: Here are some phots of the project...