Solarfriend # 1.  Discontinued no longer for sale.

Uses Pic 16F676 Microcomputer.

Needs a 7 to 15 volt supply and two temperature probes for a minimal no frills system. Three controls.

Control 1 = Diff. Switches on the relay when panel probe is hotter than tank probe by the temperature difference of this control 0 to 25 degrees C approx.

Control 2 = On time. Relay closes for a time 0 to 25 seconds this control.

Control 3 = Off time. Relay opens for a time 0 to 25 seconds adjustable. by this control.

Relay has three terminals. Normally open: Common: Normally closed: And can handle 3 amps at 24 volts DC. Connection to mains not recommended.

Relay on light and Too cold light that flashes every 10 minutes when shut down.

Current consumption is about 2 ma when running and about 50 ma when relay energized.

In a typical bare bones system this board will run from a rechargeable battery that is kept charged by a P/V panel. The temp probes would be on the panel and on the tank. You adjust the relay on off times to suit your pump and system. Typically 5 seconds on and 15 seconds off.

Shuts down and idles if panel temp probe is below 10C. Starts up again if panel temp probe goes above 10C.

On board trimmers can easily be replaced with 100k linear potentiometers fitted to control panel.



Solarfriend # 3


PIC 16F883 micro controller.

Supplied with two ready made temp probes.

Monitor lead acid battery and control charge level from P/V panel.

Control pump on time depending on probe difference values.

Shut down system when panel temp is lower than 18C

LCD display. Battery voltage:Panel temp:Tank temp displayed in sequence.

Pump for 4 to 10 seconds every 15 seconds depending on probe difference temperatures.