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?

Thanks.


Some esoteric answers ... just buy the correct transformer and run in a
new piece of bell wire ... its so small you will forget its there in a
weeks time.

wrote in message
...
On Wednesday, 9 November 2016 12:34:34 UTC, Syd Rumpo wrote:
On 09/11/2016 12:14, tabbypurr wrote:
On Wednesday, 9 November 2016 09:19:34 UTC, Syd Rumpo wrote:
On 09/11/2016 00:52, Dave Plowman (News) wrote:

snip

Assuming the 18v supply can provide enough current - which is likely
since
an electronic device is replacing a mechanical one (I guess) a simple
voltage regulator should do the job.

Friedland make some doorbells which will *only* work on AC. They also
make doorbells which work on 8V AC or 6V DC. The implication there is
that the bisexual ones are solenoid operated and the higher AC is
needed
to overcome the coil impedance at 50Hz.

You think it's needed. IRL solenoids are very tolerant. Try working
with them some time.

Friedland think it's needed, or at least desired. They have been making
doorbells for a very long time.

So Friedland have invented the very first solenoid
operated device that's fussy about its input have they?

Nope, they use buzzers that operate on AC and have no solenoid at all.

Come back when you know something about solenoids.

Dont bother coming back when you notice there is no solenoid.

On Wednesday, 9 November 2016 16:10:49 UTC, The Natural Philosopher wrote:
On 09/11/16 15:46, Syd Rumpo wrote:
On 09/11/2016 15:31, The Natural Philosopher wrote:

snip

Well google says that an AC solenoid will work on DC.

Of course! That's why they're made differently! It's a leftist plot!

The fact is, under some circumstances it will.

Neraly all actually.

I wonder how he proposes to design an ac solenoid that won't work on dc.

Under others it won't -
without modification to the plunger seating it may stick,

Utter total ********.

I've never encountered that, but doubtless there are folk with more experience of solenoids than me. Syd Rumpo is not one of them.


with continuous coil DC, it may overheat.

Shows how little you understand electrical theory.

In a few seconds with twice rated voltage? No chance. Doorbells have all of 1% duty cycle. Overheating simply depends what voltage you feed them - with dc you often use slightly lower voltage IFF you want them to stay on for ages. Doorbells don't do that.

There's a guy feeding a bank of solenoids over 100v to get them moving faster, then dropping to 5v to hold them on. They work like that perfectly.


It would have to be a damned big inductance to affect current, and the
whole POINT about an AC solenoid is that the shorted turn pole will
effectively be zero inductance.

And of course if its a buzzer or bell., its not being fed DC. Its being
fer with AC at a fairly decent frequency. -- 10Hz or so.



End of story.

Indeed. Ineducable ****.

Yes, you are. You think that because you know a little bit more than a
layman, you know all there is to know. In fact you are just a thick poseur.

There's no shortage of people that know something, but have no concept of how much they do & don't know. Some are also senselessly abusive.


WE had 'trembler' style doorbells in my parents house in the 50s. WE got
fed up with feeding them with lantern batteries so my dad bought a
'bell transformer' that was AC, and fed them with that. They worked just
FINE.

Of course. For low duty cycle work, solenoids are as fussy as starving rats.


NT