It has been a while since my last post, I have a new job and little time left for hobby stuff 
Anyway, I have put together the PCB for the Yet Another Power Monitor (YAPM) project and was able to do some preliminary tests over the weekend.
To re-cap: the YAPM is a low cost Arduino compatible power monitor that measures power (voltage and current) and transmits the readings to an Internet Gateway and/or one of my OLED status monitors. The goal was to make a single power supply unit, I used a transformer with two secondary windings – one for powering the thing and the other to measure the voltage. The total build cost for a fully functional unit, including the clap-on current sensor, is less than 30 EUR. The YAPM is based on the openenergymonitor.org project and compatible with emonTX code, except that it is single phase and doesn’t have temperature sensor/pulse sensor ports. I left those functions for the Funky to handle. The YAPM will typically be placed in or near the house’s fuse box, the PCB size is 5x5cm which makes it ideal to fit in a DIN rail box too. Here is how it looks:
Since the YAPM connects live to the 240V line, it is quite dangerous to handle and can provide you with a quick, yet painful transition to the other side if you touch the live connections while it is powered on. I haven’t had the chance to find a suitable box yet, but it must be enclosed for safety reasons.
I tested it briefly and it works as expected. I will build few more units for close family members, but other than that the YAPM will probably not make it out in the wild because of the reasons outlined in the previous paragraph.