DIY Solar PV Immersion Water Heater

My Mum and Dad have had a 3KW solar panel system installed over a year ago and my dad has been pleased but wanted to make more of them by heating the hot water as well. He had been looking at options like Immersun that cost anything from £349 upwards. This seemed a bit much and we were sure we could come up with a cheaper and just as effective way of doing the same job.

We found a website called http://www.talkingsolar.co.uk/. A cleaver man on there had come up with a circuit that uses an Arduino Uno. 

This is the circuit I found via a link on www.talkingsolar.co.uk

My job was also made a lot easier as a board design had been made and all I had to do was etch the boards, solder it up and assemble it! All I needed was a shopping list of parts to buy or acquire from work. (With my boss's permission!)

Triac BTA41-600B   Spiratronics (all order inc delivery £11.40)

Opto couple MOC3041-M  Spiratronics

Op amp LM358AN Spiratronics

Diode 1N914 Schottky  Free (Had Already)

8pin ic socket (Had Already)

Arduino UNO  £12.90

CT SCT-013-030  £6.87  eBay

PCB Transformer 3VA 9V+9V Spiratronics

Terminal block 2 way x5  Spiratronics

3.5mm stereo pcb jack  Free (Had Already)

Resistor 180R .25w metal film Free (Had Already)

Resistor 330R .25w metal film Free (Had Already)

Resistor 360R .25w metal film Free (Had Already)

Resistor 12K .25w metal film Free (Had Already)

Resistor 15K .25w metal film  Maplin £1.40

Resistor 150K .25w metal film Maplin £0.96

Fuse holder CPC £0.66

PSU for Arduino 12V .5A Free (Had Already)

Case 194.5x145x78mm  eBay The Allendale stores  £6.90

Heatsink Free (From Scrap Plasma TV)

Cable glands PG11 x 2 CPC £1.10 (only used one in the end)

Ferric chloride EBay £5.19 ( had lots left for future projects)

Total = £47.38

Here is the assembled box just before we installed it.

Here is the finished and installed "Magic Box" (as my dad calls it)

It works much better than I had hoped, my dad has turned off the gas heating for the hot water and so far he reckons that the water is hotter than it was before and they are saving on there gas bill!

Job done!