Bell push.

Fitted a new one today - illuminated. But a rather feeble yellow glow - not really obvious in daylight. And a reason for an illuminated one was to try and tell a delivery type it works, and ring it rather than knocking. The lamp fitted a hole that looked about right for an 3mm LED so had a play. But actually used two LEDs, since there were two holes for lamps.
First play with a single rectifier diode produced a very noticeable flicker, so managed to cram in a bridge rectifier and smoothing cap into the recess in the architrave.
And 20mA proved too bright. Ended up at 8mA.
But don't much like the rather odd white of cheap LEDs. Think I might change them to blue.
--
*I was married by a judge. I should have asked for a jury.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Dave Plowman (News) wrote:

I used two LEDs in inverse parallel, sharing a resistor to limit the current, yes some flicker but I didn't have room for full wave rectifier and smoothing
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Yes. I'd already got a fairly large hole in the wood architrave for an older flush push, so room in that. Could be a problem with a PVC frame. ;-)
--
*I must always remember that I'm unique, just like everyone else. *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Dave Plowman wrote:

An advantage of a PVC frame (with steel square section reinforcing inside) was that I could feed the wire invisibly to the bell push (and another to the alarm reed switch) while installing the door.
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On 19/09/2017 00:20, Dave Plowman (News) wrote:

Does it really matter that you don't like the colour temperature of the LEDs? You are only likely to see them for a couple of minutes per week. The idea is to make the bell push more obvious to visitors so maybe the brighter the better and the more garish the better.
If you make the LEDs in the bell push bright enough it can double as a porch light :)
I have some 5mm LEDs sold on Ebay as 'ultra bright' that can be seen outdoors in daylight at 5 metres running at much less than 1mA.
To make the bell push more obvious mount it on a clear acrylic sheet that is slightly larger than the bell push. Drill a hole in the middle of the sheet (hidden by the bell push) and then edge illuminate the hole with a few (surface mount) LEDs. The sheet will glow and the outside edges will be illuminated. You may have to polish the edges.
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wrote:

If you have the conventional bing bong bell chime one thing to bear in mind is that the current for the bell push lamp passes through the solenoid all the time The circuit is transformer - bell push (with light in parallel to the push) - solenoid - transformer. If you put too high a power lamp (anything over 20mA or so) in the bell push the chime solenoid carries this current and the striker remains permanently biased over to one side so the bell no longer rings reliably.
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Peter Parry wrote:

Don't the incandescent bulbs pull more than that? I would have expected it to take more than that to move the striker, I think I settled on 10mA for the LEDs.

I did wonder about needing a snubber to avoid back EMF from the solenoid harming the LEDs, but there wasn't enough space in the push for a capacitor of any non-trivial value, so I didn't bother and they've been fine without so far.
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wrote:

If it's operating on DC, another possibility would be a reverse bias diode across the chime solenoid.
I am revamping an old Freidland Westminster chime with a microprocessor to replace the warn-out paxillin rotary switch sequencer, and intend to use diodes to protect the driver transistors.
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On 19/09/2017 12:15, Graham. wrote: diode across the chime solenoid.

Some of us have too much spare time!
:-)
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Nope. ;-) The true spirit of DIY.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On 19/09/2017 13:12, Dave Plowman (News) wrote:

Don't disagree. I did a lot of electronics until I was in my mid 30's, but then shifted more to mechanics and materials. It is undoubtedly exactly the sort of thing I would be doing now had I kept up better with electronics.
Have just spent half a day fabricating a pair of steel brackets that I could (almost) have bought for £30, just because I could (and I still have an hour or so of welding to do on them).
:-)
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On Tuesday, 19 September 2017 12:15:43 UTC+1, Graham. wrote:

*nice*
A wiki article, please :-)
I always wondered how they worked, and thought it odd that George and Mildred Roper had one, but the rather more upmarket Fourmiles next door made do with a rinngbbbzzz.
Owain
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