DC from AC line without completing circuit? - Page 1
Forum section: electronics / beginners

author: MrTimcakes
author_rank: Newbie
timestamp: September 03, 2015, 02:00:20 pm
content: Hey,I've been looking at these remote light switches,goo.gl/QvH6UU,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 splice in my own guts, probably an Espruino (Possibly ESP8266 ESP-09) to add a timeout so the light goes off after a few hours or control it via WiFi.A simple circuit diagram of how this magical device works would be helpfulP.S: Espruino is a javascript interpreter designed to run on chips like STM32's more info hereEspruino.com

author: bktemp
author_rank: Super Contributor
timestamp: September 03, 2015, 02:08:20 pm
content: It is connected in series with the load, but draws low enough power to turn the lightbulb not on.It uses a triac for switching the load and it switches the load never fully on (similiar to a dimmer switch using phase angle control), so there is a still high enough voltage drop across the switch to power the circuit.But this only works for normal light bulbs but not for LED lights. So it is almost useless today as a light switch.

author: thejoggingmat
author_rank: Regular Contributor
timestamp: September 03, 2015, 02:11:01 pm
content: Quote from: MrTimcakes on September 03, 2015, 02:00:20 pmIf you look at the picture here,The circuit shows a 'neutral' from the bulb. If you interpret it another way, the bulb is wired in series with the switch (and the microcontroller and what have yous).For a moment, I really thought the Chinese had found a way to conduct to ground wirelessly through the insulated walls.

author: helius
author_rank: Super Contributor
timestamp: September 03, 2015, 02:23:05 pm
content: I love how they have drawn the Edison socket wired backwardsAlso, is this kind of switch code compliant if the socket is live even when the switch is off?

author: Chris C
author_rank: Frequent Contributor
timestamp: September 04, 2015, 09:17:04 am
content: Most CFL light bulbs, and maybe some LEDs too, accumulate charge on their internal capacitors as a result of the small current flowing through that switch when it's turned off.When it accumulates enough, they light up. But not for long, since the capacitor doesn't hold much. That process repeats, with the light "flickering" as often as several times a second, most easily seen in a dark room.That's why they include the "gift" capacitor. It provides a way for small AC currents to travel around the bulb, rather than through it.I've eliminated flicker, and made switches like these work with bulbs they would otherwise refuse to work with, a variety of other ways too. Many of my old remote control switches have AC plug inputs and outputs. So I just plug a two-way splitter into the switch, plug the lamp into one receptacle, and something else into the other receptacle. Sometimes an old transformer-based "wall wart" power supply is sufficient. Old mechanical timers like these work well too:The motor inside draws enough current to allow the switch to work properly, and prevent the bulb from flickering. Other things, like incandescent night lights, can work too.