Led/Optocoupler protection circuit question.

[hozone]

Hello,

I've a question about a protection circuit.
First of all, I'm not a electronic eng, so excuse me for my lack of knowledge, and excuse my poor english too
My home alarm have a status indicator LED, when the alarm is engaged that led is powered up. The led is powered up by a optocoupler and a indipendet supply. Led resistor is on alarm side. On the led and switch sockets I've just the led connected.
I've a "strange" behavior:w ehenever i press the switch that turns my lounge on, the led emits some light.
Led wires runs parallel to the main AC supply cables, 220V here in Italy.
My thought is that when I switch on the room lights, induced EMF produces current on the led cables, and that makes the led blink.
I've two questions:
1- What do you suggest me to at least protect the led from overvoltage (led side)?
2- Have i to build a protection circuit for the optocoupler too (alarm side)?

thank you!

[jeroen79]

Exactly what kind of circuit is it?
Like this?

There is no resistor on the other side of the optocoupler or  by the LED or it's power supply?

What kind of wiring are you using for the LED?
If it gets interference from the mains wiring then you could move it away from the mains or replace it with shielded wires.

[hozone]

Thank you for reply.
Yes, one resistor is left in your image. It's something like the attached image.
It's not twisted pair wiring the led one.
The only way i can get that led out is by the power lines duct.