Maker Pro
Maker Pro

Doorbell button spark

K

Kroma

Jan 1, 1970
0
Hello,

I recently installed a wired doorbell and it works very well indeed.

However... I was leaving the house in the dark (and it was VERY dark)
this evening and pushed the bell push in order to hear how loud the
doorbell would be to callers. I was shocked to see that the bell push
briefly lit up as I released the button. As it is not an illuminated
bell push (I have the unit installed with batteries) and owing to the
fact that the light had a blue tint, I am assuming that the light I
saw was in fact a spark within the bellpush. There was no spark as I
pressed the button - only on release. In fact the spark isn't visible in
daylight - it has to be VERY dark!

In all other respects the unit appears to be working perfectly well
and the spark isn't apparent during daylight but can anybody tell me
what could be causing the spark or is this normal? I had checked the
bell push very carefully before securing everything in place and the
connections appeared to be good.

Thanks in advance,

Daz
 
F

Funfly3

Jan 1, 1970
0
perfectly normal
Kroma said:
Hello,

I recently installed a wired doorbell and it works very well indeed.

However... I was leaving the house in the dark (and it was VERY dark)
this evening and pushed the bell push in order to hear how loud the
doorbell would be to callers. I was shocked to see that the bell push
briefly lit up as I released the button. As it is not an illuminated
bell push (I have the unit installed with batteries) and owing to the
fact that the light had a blue tint, I am assuming that the light I
saw was in fact a spark within the bellpush. There was no spark as I
pressed the button - only on release. In fact the spark isn't visible in
daylight - it has to be VERY dark!

In all other respects the unit appears to be working perfectly well
and the spark isn't apparent during daylight but can anybody tell me
what could be causing the spark or is this normal? I had checked the
bell push very carefully before securing everything in place and the
connections appeared to be good.

Thanks in advance,

Daz
perfectly normal for a battery doorbell its caused by back EMF
http://www.physics.brown.edu/physics/demopages/Demo/em/demo/5j1023.htm it
can give you quite a shock
 
R

Ross Herbert

Jan 1, 1970
0
Hello,

I recently installed a wired doorbell and it works very well indeed.

However... I was leaving the house in the dark (and it was VERY dark)
this evening and pushed the bell push in order to hear how loud the
doorbell would be to callers. I was shocked to see that the bell push
briefly lit up as I released the button. As it is not an illuminated
bell push (I have the unit installed with batteries) and owing to the
fact that the light had a blue tint, I am assuming that the light I
saw was in fact a spark within the bellpush. There was no spark as I
pressed the button - only on release. In fact the spark isn't visible in
daylight - it has to be VERY dark!

In all other respects the unit appears to be working perfectly well
and the spark isn't apparent during daylight but can anybody tell me
what could be causing the spark or is this normal? I had checked the
bell push very carefully before securing everything in place and the
connections appeared to be good.

Thanks in advance,

Daz

When asking questions like this it is best if you give make/model
and/or operating principle (or the sound it makes).

Here's my guess. If the doorbell is battery powered and uses a
solenoid to strike one metal gong or bar when the button is pressed
and then retracts under spring tension to strike another metal gong or
bar on releasing the press button (produces the ding - dong sound),
then the sparking at the button is most likely due to back emf from
the solenoid. Nothing to worry about....
 
K

Kroma

Jan 1, 1970
0
Ross Herbert said:
When asking questions like this it is best if you give make/model
and/or operating principle (or the sound it makes).

Here's my guess. If the doorbell is battery powered and uses a
solenoid to strike one metal gong or bar when the button is pressed
and then retracts under spring tension to strike another metal gong or
bar on releasing the press button (produces the ding - dong sound),
then the sparking at the button is most likely due to back emf from
the solenoid. Nothing to worry about....

I'm sorry my info was a bit scant.

It's a Byron wired doorbell of the 'ding dong' chime bar variety. It's
battery operated. Does that still sound normal?

Thanks,

Daz
 
D

Dave Plowman (News)

Jan 1, 1970
0
As it is not an illuminated
bell push (I have the unit installed with batteries) and owing to the
fact that the light had a blue tint, I am assuming that the light I
saw was in fact a spark within the bellpush. There was no spark as I
pressed the button - only on release.

Perfectly normal with DC. That's why an AC switch has a lower rating
current wise on DC.

The effect is rather like how a basic car ignition works. Build up a flux
in an inductor, which a doorbell is to a certain extent, and then switch
off the current. The flux collapsing produces a high voltage. In an
ignition system you use a transformer (coil) to get an even higher voltage.
 
D

Dave Plowman (News)

Jan 1, 1970
0
It's a Byron wired doorbell of the 'ding dong' chime bar variety. It's
battery operated. Does that still sound normal?

Yes - the solenoid is almost a pure inductor.
 
T

**THE-RFI-EMI-GUY**

Jan 1, 1970
0
If it worries you, you can put a diode ( 200-400V PIV) across the
solenoid coil so that it is reverse biased when the solenoid is
energized. When you release the button, the diode will be forward
biased and will absorb the back EMF. There is a slight possibility this
mod might slow the solenoid release, interfering with the tone, You
have to try it to see.
Yes - the solenoid is almost a pure inductor.

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"

The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there's probably a time
when he's only partially mad. And this is the time when he's
going to throw his best parties.
 
P

petrus bitbyter

Jan 1, 1970
0
Kroma said:
Hello,

I recently installed a wired doorbell and it works very well indeed.

However... I was leaving the house in the dark (and it was VERY dark)
this evening and pushed the bell push in order to hear how loud the
doorbell would be to callers. I was shocked to see that the bell push
briefly lit up as I released the button. As it is not an illuminated
bell push (I have the unit installed with batteries) and owing to the
fact that the light had a blue tint, I am assuming that the light I
saw was in fact a spark within the bellpush. There was no spark as I
pressed the button - only on release. In fact the spark isn't visible in
daylight - it has to be VERY dark!

In all other respects the unit appears to be working perfectly well
and the spark isn't apparent during daylight but can anybody tell me
what could be causing the spark or is this normal? I had checked the
bell push very carefully before securing everything in place and the
connections appeared to be good.

Thanks in advance,

Daz

Every time you interrupt a current flowing with a mechanical switch you will
have sparks. Even when you switch on you can have sparks due to the
contactbounce. During daylight you will not see them but you can often hear
them through an AM radioreceiver. Your lightswitches in the house will also
spark although you may not see them. They can can for instance ignite
gasexplosions (if there is gas in the room of course.) Doorbellswitches will
spark even more because of doorbells contain coils and the back EMF will
give a high voltage pulse when you switch off. You can try to reduce the
sparking by placing a capacitor over the switch. But there's no reason to
worry. Millions of doorbellswitches are sparking every day and you only
realize it because you saw it in the dark.
BTW. Did you ever put off a shirt or a pully (wool or synthetic, cotten
hardly sparks) and hear the crackling of *that* sparks? You can even see
them when its dark enough.

petrus bitbyter
 
K

Kroma

Jan 1, 1970
0
Thank you for your in-depth replies everybody! I have now stopped panicking
and will leave the doorbell as-is!

Thanks again,

Daz
 
A

Arfa Daily

Jan 1, 1970
0
Kroma said:
Thank you for your in-depth replies everybody! I have now stopped
panicking
and will leave the doorbell as-is!

Thanks again,

Daz
To add to Dave's excellent analogy of the car ignition system ( or at least
the old Kettering ignition that used to be fitted, rather than the new
fangled electronic variety that they now have ), you can suppress the
contact arc by fitting a capacitor of somewhere between 0.1 and 1.0uF and
rated 200 to 400v, across the bell-push contacts. The sparking that occurs
is the exact reason why such a capacitor ( also known in the motor trade as
" The Condenser, mate " ) is fitted across the points in the distributor
head. There is a school of thought, however, that with intermittently used,
unplated contact sets, such as are to be found in bell pushes, it's a good
idea to let them spark, as this keeps the oxide layer, which inevitably
builds up on the contact faces, ' punched thru ' to clean contact metal.

Arfa
 
D

Dave Plowman (News)

Jan 1, 1970
0
To add to Dave's excellent analogy of the car ignition system ( or at
least the old Kettering ignition that used to be fitted, rather than
the new fangled electronic variety that they now have )

Still the same principle of cutting off the current flowing in an
inductor, though, - it's just that the mechanical switch in the form of
points has been replaced by a more sophisticated electronic one.
, you can suppress the contact arc by fitting a capacitor of somewhere
between 0.1 and 1.0uF and rated 200 to 400v, across the bell-push
contacts. The sparking that occurs is the exact reason why such a
capacitor ( also known in the motor trade as " The Condenser, mate " )
is fitted across the points in the distributor

IIRC, it also formed a tuned circuit to improve efficiency.
 
A

Arfa Daily

Jan 1, 1970
0
Dave Plowman (News) said:
Still the same principle of cutting off the current flowing in an
inductor, though, - it's just that the mechanical switch in the form of
points has been replaced by a more sophisticated electronic one.

And the coil has been replaced by a quad unit that doesn't require a
distributor ...

;-)

IIRC, it also formed a tuned circuit to improve efficiency.

Very probably. Years ago, I built many electronic ignition units for
friends, based on a circuit published in Practically Witless magazine. That
had a CTV 0.47uF 1000v boost resevoir capacitor in the output, effectively
placed in series with the coil. It was charged to a high voltage, then
dumped into the coil by a thyristor, controlled by the points. This caused
the coil to ring as an LC tuned circuit with the cap. This resulted in a '
long ' spark, which was basically AC, thus having the effect of making the
plug electrodes last much longer, as no metal migration took place. The plug
gap was increased to around 50 thou as I recall, to take advantage of this
massive long AC spark. I also seem to recall that this circuit still pushed
a comparitively significant current through the points, via a resistor, to
overcome the oxidation insulation problem that I mentioned. It was essential
that a new set of points was fitted at the same time as the ignition unit,
otherwise, the engine would soon come to a stop due to the quick oxidation
of the ( already ) burnt points surface.

These ignition units were so good ( remember the commercially available "
Sparkrite " models - three of them as I recall ) that when I took one off of
a car that I was about to sell, the engine, which had been running
perfectly, turned out to be so far out of tune, that it wouldn't even start.

I guess all modern cars now have something along these lines, which accounts
for why, in conjunction with the automatic self tuning engine management
sytem, modern engines can go 20,000 miles between services, and start first
flick of the key, under all weather conditions.

Arfa
 
D

Dave Plowman (News)

Jan 1, 1970
0
And the coil has been replaced by a quad unit that doesn't require a
distributor ...

But still coils. So the same principle. ;-)
Very probably. Years ago, I built many electronic ignition units for
friends, based on a circuit published in Practically Witless magazine.
That had a CTV 0.47uF 1000v boost resevoir capacitor in the output,
effectively placed in series with the coil. It was charged to a high
voltage, then dumped into the coil by a thyristor, controlled by the
points. This caused the coil to ring as an LC tuned circuit with the
cap. This resulted in a ' long ' spark, which was basically AC, thus
having the effect of making the plug electrodes last much longer, as no
metal migration took place.

Capacitive discharge.
The plug gap was increased to around 50
thou as I recall, to take advantage of this massive long AC spark. I
also seem to recall that this circuit still pushed a comparitively
significant current through the points, via a resistor, to overcome the
oxidation insulation problem that I mentioned. It was essential that a
new set of points was fitted at the same time as the ignition unit,
otherwise, the engine would soon come to a stop due to the quick
oxidation of the ( already ) burnt points surface.

It got round one problem but caused others? At least you could switch it
back to points if the electronics failed. As they often did.
These ignition units were so good ( remember the commercially available
" Sparkrite " models - three of them as I recall ) that when I took one
off of a car that I was about to sell, the engine, which had been
running perfectly, turned out to be so far out of tune, that it
wouldn't even start.

Yes - dwell angle is important with points to give the coil enough time to
build up the correct flux. Not so with CD.
I guess all modern cars now have something along these lines, which
accounts for why, in conjunction with the automatic self tuning engine
management sytem, modern engines can go 20,000 miles between services,
and start first flick of the key, under all weather conditions.

Well, many modern cars will do 100,000 miles without the ignition system
being touched in any way - long life plugs. If it doesn't break first, of
course. Servicing consists more of just changing some fluids and filters.
 
A

Asimov

Jan 1, 1970
0
"Kroma" bravely wrote to "All" (23 Sep 05 10:45:42)
--- on the heady topic of "Doorbell button spark"

Kr> From: "Kroma" <[email protected]>
Kr> Xref: core-easynews sci.electronics.repair:342888



Kr> Hello,

Kr> I recently installed a wired doorbell and it works very well indeed.

Kr> However... I was leaving the house in the dark (and it was VERY dark)
Kr> this evening and pushed the bell push in order to hear how loud the
Kr> doorbell would be to callers. I was shocked to see that the bell push
Kr> briefly lit up as I released the button. As it is not an illuminated
Kr> bell push (I have the unit installed with batteries) and owing to the
Kr> fact that the light had a blue tint, I am assuming that the light I
Kr> saw was in fact a spark within the bellpush. There was no spark as I
Kr> pressed the button - only on release. In fact the spark isn't visible
Kr> in daylight - it has to be VERY dark!

Kr> In all other respects the unit appears to be working perfectly well
Kr> and the spark isn't apparent during daylight but can anybody tell me
Kr> what could be causing the spark or is this normal? I had checked the
Kr> bell push very carefully before securing everything in place and the
Kr> connections appeared to be good.

Kr> Thanks in advance,

Kr> Daz


When the button is closed some energy is stored outside the wire just
like an electromagnet. When the button is released that collapsing
magnetic energy induces charges in the wire. However the switch
contact is open leaving only air which has a very high resistance. The
induced charges generate a high voltage which ionizes the air path and
allows a current to flow. The longer the wire the greater the voltage.
The resulting spark is like a mini thunderstorm.

A small network called a snubber, which consists of a resistor and
capacitor in series, can be placed across the arcing contacts to
safely dissipate the stray inductive energy and eliminate sparking.

A*s*i*m*o*v

.... Chico of Borg: "Resistance? Atsa no good!"
 
Top