DIY isolator...

[TaDa]

Hi!

I have a circuit that normally runs from a mains power supply (with a resistor, rectifier and zener) that I want to control using a small battery powered circuit.
But the -ve side of the mains circuit is, effectively neutral(?) and I don't really want the negative side of the battery circuit to become neutral

Are there any isolator circuits I can make from common (all garden) components (rather than buy an opto isolator)?

Cheers

 

[MikeMl]

Hi!

I have a circuit that normally runs from a mains power supply (with a resistor, rectifier and zener) that I want to control using a small battery powered circuit.
But the -ve side of the mains circuit is, effectively neutral(?) and I don't really want the negative side of the battery circuit to become neutral

Are there any isolator circuits I can make from common (all garden) components (rather than buy an opto isolator)?

Cheers

Transformer. Do you have an old unused Wall-Wart charger laying around?

 

[crutschow]

Mike, the OP stated that the circuit is operated from the mains voltage, so unless he can redesign it to operate from the output of a Wall-Wart, that won't work.

You could use an isolator transformer on the mains but that would be more expensive than an opto isolator.

 

[MikeMl]

Mike, the OP stated that the circuit is operated from the mains voltage, so unless he can redesign it to operate from the output of a Wall-Wart, that won't work.

You could use an isolator transformer on the mains but that would be more expensive than an opto isolator.

He also stated that the Line-powered circuit is no more than: I have a circuit that normally runs from a mains power supply (with a resistor, rectifier and zener) that I want to control using a small battery powered circuit.
But the -ve side of the mains circuit is, effectively neutral(?) and I don't really want the negative side of the battery circuit to become neutral, so grab a Wall-Wart (which is what he should have done in the first place; I wince when Newbies are screwing around with line-powered circuits, especially 240V ones), and rebuild it so everything is downstream from the Wall-Wart.

I have dozens of old Wall-Warts in my junk box for projects such as this...

 

[TaDa]

Thanks people...

As ever I've skimped on the original request! Apologies...

My 'mains' device is one of those freebie mains switches that turns on/off from an IR signal.
Ultimately these things have a relay that switches the mains but they have a small circuit (fed from the zener etc) to power the whole thing. The relay is 24 v and is turned on/off using a surface mount transistor.

I want to replace the IR trickery with a simple low power circuit that fires the transistor, powers the relay and switches the mains.
The problem is, though, to fire the transistor I need to share the ground with my battery switching unit.
I know the correct solution is to use an opto-isolator - but I'm being cheap (again!) and I don't have one in my box of bits.
I'll probably have to wait until I have a bigger order add remember to add one to the order but it would be nice to progress my little project now - using more bread and butter components.

I'm not too sure a transformer would do this (I also have space constraints ( I want to wedge most of it back into the original case)).
I suspect a relay would do the deed - but I don't have one of those either

Anyway, I'm beginning to think that the opto-isolator is the only way forward.