I wanted to monitor my water use. I decided to start in the workshop as this supply fed the garden. Then I would expand to monitor the house use as well. All this with a view to see if it was worth while moving over to a Welsh Water watermeter instead of paying water rates. I bought, off ebay, a couple of standard water meters (secondhand) for £6. These had a silvered six pronged star shaped wheel that rotated as the water flowed. I found, from maplins would you believe, a tiny little IR tx/rx device that with some work would sense the rotation of this wheel.

The sensors active face has depressions in it that interfered with the transmision of the light through the clear face of the watermeter.

I ground these depressions off with wet and dry paper 600 grit.

then polished the front of the sensor with Metal polish on paper to restore the optical finish.

this is the now flat faced sensor before glueing to the front of the water meter.

The sensor required an interface cct to enable the generic controler to count the pulses from it. this was put on vero board it's a lot quicker than doing a PCB.

The interface cct basically squared up the pulses and ensured they were 0-5V.

The finished job ready to install. The black lid was not part of the water meter but helps the sensor work properly.

this is the installed and working water meter. The blue tack is for cable strain relief and to hold the black lid on...