DC from AC line without completing circuit?

[espruino-discuss3]

Posted at 2015-09-02 by MrTimcakes

Hey,
I've been looking at these remote light switches and I'm wondering how they get power to power the micro-controller inside used for 433mhz and captivate touch sense without turning on the light-bulb attached, I know they don't use a battery. I'd like to rip one apart and attach an Espruino (Possibly ESP8266 ESP-09) to add a timeout so the light goes off after a few hours or control it via WiFi.

[gfwilliams]

Posted at 2015-09-07 by @gfwilliams

I think you'd have to look inside them. Some of them use a Siemens chip called LightwaveRF that might include some magic, but you can also do some properly hack stuff using capacitors if you only need a small amount of power from the mains.

As they're radio based, what about intercepting the radio signal? Could you just have a totally separate board somewhere that detects when the 'on' command was sent, and that then sends an 'off' command after a timeout?