Solar pool heater controller

Controller using Arduino to monitor solar insolation and water temperatures to automate solar pool heating for most effective pump operation

J Reynoldson

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Description

This controller based on an Arduino Nano, a thermister, 2xLM35s and a solid state AC switch along with a LCD display and two switches is designed to maximise the efficiency of the use of a solar pool heating pump. One thermister is used as a solar (INSOLATION) sensor on the roof. One LM35 (POOL) is used to monitor the temperature of water entering the pum from the pool. The other LM35 (RETURN) monitors the temperature of water coming back from the solar heat array.

The controller's main function consists of a loop that checks the availablilty of adequate insolation, does a trial pump run to confirm adequate heating, continues to run the pump while heating is adequate and turns it off if heating falls below a threshold or the target pool temperature is acheived.

A LCD display shows the three sensor readings and the state of operation. A single pushbutton toggles the operation between manual and automatic operation.

CAUTION: AC VOLTAGES MAY BE HAZARDOUS!

Details

WARNINGS:

240/110 VAC power is hazardous. This is NOT a project for beginners.

Pool heating should always be turned OFF while the pool heat is running, as there is a possibility of scalding water on startup.

LM35DZ Temperature sensor information:

Search ebay for "Waterproof Digital Thermal Probe LM35DZ Temperature Probe". These probes are inserted into the PVC pump lines using a 8mm pool solar manifold grommet.

AC power notes:

The project is powered by the same AC supply used for the pool pump, but uses a commercial 12V wall wart built into the box to provide the required 12C DC. A relay is used to switch the pump on and off, and all AC based components are in a separate compartment of the controller.