First of all if the LEDs are connected in series (which they should be) then you actually have 3.6 -4.4 volts available. You do not say how you actuate your wireless alarm sounder. If you require to switch the device on, you need to put a transistor in series with the +12V and feed its base via a current limiting resistor fed from the LEDs. Until you give us more data (voltage and current to be switched ), we can't say anymore.
Frank
At the most basic level, a PNP transistor, in CE configuration would probably do - base goes to top of LEDs, collector to alarm, emitter to night light power (V+).
The night light looks like it uses the huge film capacitor to limit the current then rectifies the mains (120VAC or 230VAC).
The tiny battery in the alarm circuit is a 12V model A23 (not 23A) that typically can supply only a few mA for a little while.
Since the night light does not use a transformer then your circuit is deadly if any part can be touched.
The night light looks like it uses the huge film capacitor to limit the current then rectifies the mains (120VAC or 230VAC).
The tiny battery in the alarm circuit is a 12V model A23 (not 23A) that typically can supply only a few mA for a little while.
Since the night light does not use a transformer then your circuit is deadly if any part is touched.
I got my eyes fixed with new lenses a few years ago when I got blinded with cataracts. Now I can see through the clothing on pretty ladies far away!
Up close the pretty ladies can see me drooling.
An opto-isolator seems like a great idea -- from what I've read - although I don't know how it works - a little 6 leg chip.
There is no power on the alarm side only when the alarm signal is being sent.
The only continuous power is on the night light side.
Here was an idea - based on your opto-isolator -- would there be any way to just solder an ldr onto the alarm sensor, that once it picked up the light from the led in the night light -- allowed the alarm circuit to be made?
From what I've read an ldr varies the resistance depending on the amount of light - so it would need to be changed to let the full 12v pass though the alarm with any light from the night light.
Do you think I should scrap the night light circuit - and just try and build my own - non-dangerous circuit?
Here was an idea - based on your opto-isolator -- would there be any way to just solder an ldr onto the alarm sensor, that once it picked up the light from the led in the night light -- allowed the alarm circuit to be made?
Maybe it would be simpler for you to change the power supply on the night light - trace it to where the voltage is DC, rip out the components from there back to AC, and then power from a wall-wart.