Archive for Alex

Measuring electricity consumption

I soldered a BPW85C photo transistor onto some CAT5 cable, and connected it to an input on the QTI module, which is near my electricity meter. I was able to lodge the cable in a suitable place to ensure that the end of the photo transistor is right in front of the flashing LED on the meter.


1,000 pulses of the LED = 1kW. Cortex has a pulse meter object, and it all worked first time!

meter_outputI’m currently using 3.96kW, and will add some graphs once they’ve populated.


Hot water control

The Idratek module is now connected and working. It fails safe on HW on, so in the event of the network going down, the hot water will come on.

What I am now attempting to do is to sense whether the pipework from the boiler is heating up when the HW system calls for heat. That way, if there is a problem (boiler hasn’t fired), the immersion heater will switch on instead, and generate a warning.

After some discussion on the Idratek forum, it made sense to monitor the output of the grey wire on the 3-port valve. This goes live when either the HW is off, or the HW is on but the cylinder thermostat has reached its temperature and is therefore not calling for heat. Logically, if the above is false, and the system is calling for heat to heat the hot water, then the pipework should be getting hot.

neonMy first challenge is to sense when the grey wire is live. I have added a neon indicator (240v) to that wire and neutral, which will be on when the HW is either off or not calling for heat.