This is an RF wall switch

but it uses only LIVE + LOAD1 cables like in the wall lamp switch
(2 wires wall switch, load and live)

If you short LIVE and LOAD the lamp turns on

LIVE 220V------[SWITCH]-----LAMP----GROUND

This RF switch replace the mechanical switch and toggles by touch the lamp with relay, and can do it by rf 433mhz.

But how does it get power and keep the lamp off, if it disconnect the LOAD cable it will shut it's own power off.

I believe it keep some kind of always connected LIVE+LOAD with low resistance when "OFF" so the IC will keep geting his power, but the lamp will say off because the current is too low or something like that. Can anyone shade some light on this? :)

Does anyone has any schematics that will allow me to replicate this device to operate a 5v micro-controller with relay on 220v live line & load.

I have a 220v to 5v power supply.. IC and relay lke that:

LIVE 220V + -------- [ 220V-5V + IC + relay ]--------LAMP -----GROUND

Try to keep the micro-controller on 247, and the relay to toggle the lamp,

how can it be done? what part do i need? anyone done that before?

thanks allot...

EDIT: adding my draw :)

a little drawing of how it should be

so what do i need to put instead of the "?" compnent? is it a current limiter? does anyone can give me a schematics of current limiter that will lower the amps to low as 50mA-150mA but keep it 220v? technically i need a "constant" lamp dimmer on his lowest setting but not off, right?


  • 4
    \$\begingroup\$ "Max current 5A" and "Total rated load 2000W" ... if its specs contradict themselves so blatantly, trust it at your peril. To answer your question, the spec contains the line: "Lamps for Switch:All kinds of lamps, but need to over 15W". It won't work reliably if the load impedance is too high : that implies it powers itself by conducting (a little) even when off. If you use one of these, put it in series with a real switch! \$\endgroup\$
    – user16324
    Commented Jan 15, 2015 at 23:13
  • \$\begingroup\$ hi, thanks for your answer, but how do i "conducting a little"? is there any electrical component that i can connect to achieve this goal? \$\endgroup\$
    – itai
    Commented Jan 15, 2015 at 23:20
  • \$\begingroup\$ You will get better responses if you tidy up your presentation somewhat. Start sentences with capital letters, use complete sentences. Avoid eg "hell" and words which do not add to meaning. You may not feel these points count for much but they can greatly affect how your questions are received. I tidied your question up somewhat. \$\endgroup\$
    – Russell McMahon
    Commented Jan 16, 2015 at 8:49
  • \$\begingroup\$ thanks,point taken. English is not my native language..., still searching for an answer if anyone got a schematics to do this kind of thing... \$\endgroup\$
    – itai
    Commented Jan 16, 2015 at 12:03

2 Answers 2


-Switched off: It draws current through the bulb. The current it draws is not enough to visibly light up the bulb. Certain type of LED bulbs may cause trouble with this switch though, as they prevent the switch from drawing enough current.

-Switched on: In creates a voltage drop of a few volts to keep the electronics active. The drop in brightness is not noticeable to the average human.

Regular phase-cut dimmers work in the same way.


As you guessed they leak through the load when in the off state. Automated light switches have been doing this for years. It is not too big of a deal with incandescent lights, but it does cause issues at times with fluorescent ballasts (especially the lower quality ones).

It's been years since I've worked on one of these, but the general idea is to use a different circuit for the OFF state and the ON state. The two power supplies are switched when the state switches. I don't have the circuit diagrams anymore, but that was how it was done. Note that this was for an occupancy product sold to commercial spaces in the US. It is a perfectly safe, viable method, was UL certified (Type I), etc.

In the OFF state, there is a large voltage across the two connectors, but only a low current is allowable. So a step down transformer was used to get the AC down to the right level with good power conversion. Then it was rectified, regulated, etc.

In the ON state, there is a small voltage drop, but plenty of current, so a step up transformer was used.

  • \$\begingroup\$ did this work(you mentioned that it had some issues with fluorescent ballasts)with all types of loads ?? Incandescent, flourescent, led, cfl?? One more question. Since there was supposed to be a low current path. Were any measures taken limit the current in worst case scenarios(like if I touch the p-n, thinking that thr switch is off)? \$\endgroup\$ Commented Mar 12, 2016 at 19:33
  • \$\begingroup\$ We never did much with the CFL's but the rest work fine. The lifetime of lamps on low-quality fluorescent ballasts can be reduced due to the weak load being applied to the actual lamps. (The ends of the lamps have a very subtle glow in the dark.) As far as current limiting, if you touch p-n, there's nothing that can be done. You went around the current limiter. \$\endgroup\$
    – caveman
    Commented Mar 14, 2016 at 22:18
  • \$\begingroup\$ Hmm I get it. My main doubt was, did the circuit close in case of fluorescent and led? \$\endgroup\$ Commented Mar 15, 2016 at 2:56

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