Switch lamp with two serial switches

Question

I have a lamp, with the usual built-in switch, which is powered via a wall-mounted socket. The socket is switched itself with a normal wall switch. So, both switches operate in series, the lamp lights only if both switches are on.

I am looking for a way to flexibly switch the lamp on and off: from the lamp switch regardless of the wall switch and vice versa.

I am thinking about replacing both switches with push-buttons which would power the wires, execept one button is pressed. Then I would need some device the lamp which is able to detect a button push (voltage drop), to survive the short power outage while in operation and to actually switch the lamp.

Any ideas how such a device could look like?

I have rather limited space in the lamp body for installing additional components. I am in Europe with 230V AC. I have no means of adding another wire between the two switches due to in-wall mounting of the cable between socket and wall switch.

I am prepared to build something myself, just don't know in which direction to think.

Answer 1

Indeed, you need to at the very least replace the circuit breaker to some sort of signal instead, as otherwise you wont be able to power the lamp. If you were to send the signal as a brief lack of power, you need some to make some bi-stable circuit in the lamp to do the switching.

I would recommend using a micro-controller and bi-stable relay. I would power the µC from a diode bridge and a capacitor, and use the EEPROM to remember the state of the device, and use the brownout/power reset to trigger a switch, i.e. to actuate the relay.

Now any simple push-button in a series chain (i.e. both your wall button and cable button) will trigger a toggle.

I hope you have space for a relay in your lamp-side circuit, as switching mains AC in any other way will be much more complicated...