On 08/11/2016 21:25, wrote:
On Tuesday, 8 November 2016 18:31:17 UTC, Syd Rumpo wrote:
On 08/11/2016 17:59, The Natural Philosopher wrote:
On 08/11/16 17:43, Syd Rumpo wrote:
On 08/11/2016 15:34, WeeBob wrote:
Hello.

I have an old wired doorbell that has an 18V DC power supply. The
actually transformer has been (I think) channelled into the wall, or
underfloor boards in the attic. i.e. hard to get to.

A new fancy doorbell requires connection to a 8V AC power supply.

Is there a simple way to do this? i.e. 18V DV in, 8V AC out?

If the power so low enough and audio amplifier fed from a 50Hz
oscillator is one way.

the audio amp can be the oscillator.

Would you *seriously* fit that yourself rather than use a bell
transformer designed for continuous use?

I'd use a voltage regulator.

Do you know it will work with DC?

It's not simple,

it is

not
certified,

what's that got to do with anything?

certainly not as reliable

no less reliable than any electronics. If you're competent you can do it to mil spec.

A mains transformer designed specifically for continuous use is more
reliable than a bunch of electronics. Why would you even argue the point?

and awkward to explain to the
insurance company when the firemen have left.

no it's not. Insurance doesn't exclude electronics, and it's trivial to make it not a fire risk.

The only thing that might need ac is some small bells that work the wacker at 50Hz.

And this might well be one. The Amazon reviews of a Friedland 8V AC
doorbell suggest a 'Brrrrrrrrh!' sound.

Like this, perhaps...
https://www.youtube.com/watch?v=VWwk76SEAno

Or if it's a simple electromechanical 'ding - dong' type using a
solenoid actuator then there is a difference between AC and DC
solenoids, just as AC and DC relays are different.

Wind your neck in, bellend.

Cheers
--
Syd