"David Robinson" wrote in message
...
I share this with the group in case the conclusion (wire the bells in
series, not parallel) is useful to anyone, and to see if anyone has
any better advice about all this! And whether to use a snubber or
not...


I tried to follow this...
http://wiki.diyfaq.org.uk/index.php?...es_explain ed
...when installing my new door bell.

One push, one transformer, two ding-dong bells in parallel.
push:
http://www.tlc-direct.co.uk/Products/VE814.html
bells:
http://www.tlc-direct.co.uk/Products/VE117.html

With the standard transformer from tlc...
http://www.tlc-direct.co.uk/Products/TCTR7.html
...it worked OK on the 12V winding, but with two issues:
1) while the door bell is pushed in (i.e. between the "ding" and the
"dong") the AC made the bells buzz/hum
2) good old transformers use electricity even when the bell isn't
being pushed

I though a switched mode DC PSU could solve both problems, so tried to
figure out what to buy...

The bells were rated 8-16V. 9V batteries or 16V transformer were
suggested on the packaging, 1A load. I was quite surprised they'd
worked in parallel from the 12V 1A transformer, but they seemed fairly
happy with it.


I referred to the FAQ, and saw that I needed plenty of voltage and
current. Taking all things into consideration, I chose this...
http://cpc.farnell.com/stontronics/d...70?Ntt=PW02470
1.25A, 15V.

Long story short, it does this:

1) one bell - works, but with such force that the initial "ding" is
more like a "BANG" that's going to shoot the sounder through the wall
2) two bells in parallel - holding the door bell push in (i.e. you'd
just expect a "Ding"), you get a ding ... dong-ding ... dong-ding ...
etc. Seems the PSU has some sort of short-circuit or overload
protection that kicks in.
3) two bells in series - fine.

So, that was the solution: put the bells in series. Works fine, but
I'm wondering if a lower powered PSU with the bells in parallel might
have been a better solution, or worse?

Also, for just one bell, when using a switched mode PSU, it seems you
need far less voltage (or current) than the packaging or FAQ would
suggest. Not that I've tried it - but with 15V 1.25A, I don't think
the bell is going to last long, and while it lasts, it won't make a
very nice "Ding"!


In all cases, the crackle in the door bell push itself is quite
considerable. I could try a snubber, but I'm worried that's just going
to draw a little current 24/7 - the whole point of the switched mode
PSU is that it draws basically nothing when there's no load (i.e.
99.9999% of the time).

Skinflint that I am, I'm trying to do the mental calculation of the
cost of replacing the door bell push when it's prematurely worn out
due to the arcing, vs the cost of the current drawn by a snubber. But
I can't begin to figure it out!

Cheers,
David.

We could have a whip-round and get you a new bell-push