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AC or DC????????????

K

Kim Sleep

Jan 1, 1970
0
I recently acquired a beautiful antique doorbell from Russia, and there are
absolutely no markings on the electromagnets.
Is there a way that I can tell the voltage (this I can probably ascertain
from applying increasing amounts of voltage), but how can I tell if its AC
or DC?. I've researched bell voltages from the 50's, and they seemed to vary
quite a bit, and also seemed to be dc, almost as often as they were ac
(looks like standardization of doorbell voltages came much later)
Thanks for any help.
Kim.
 
J

John Miller

Jan 1, 1970
0
Kim said:
I recently acquired a beautiful antique doorbell from Russia, and there are
absolutely no markings on the electromagnets.
Is there a way that I can tell the voltage (this I can probably ascertain
from applying increasing amounts of voltage), but how can I tell if its AC
or DC?. I've researched bell voltages from the 50's, and they seemed to vary
quite a bit, and also seemed to be dc, almost as often as they were ac
(looks like standardization of doorbell voltages came much later)
Thanks for any help.

A DC bell will have to have a contact that breaks when the magnet is
activated. Trace the wires, and you should have your answer.
 
N

NRen2k5

Jan 1, 1970
0
Well, they make interrupter-type actuators for both DC and AC bells.
In fact, many such products are labelled for use on either AC or DC.

The important thing to observe is the actuation of the bell ringer and
the degree of arcing at the interrupter contacts. Assuming your bell
is a typical interrupter-type, in which the current through the
electromagnet coil is interrupted by contacts mounted on the clapper
arm that are pulled open for each stroke of the clapper, I'd suggest
just supplying the bell with a variable voltage supply, either AC or
DC, whichever you want to supply to the finished installation, and
increasing the voltage until you get a pleasing, reliable ringing
action with the least arcing at the contacts. I'd try both AC and DC
and see which seems to give the best actuation with the least arcing.
In a simple bell with only an electromagnet and interrupter contacts,
you won't hurt it by trying both.

You will inevetably get arcing (unless there is some sophisticated
suppression provided, which I doubt), because the contacts are
interrupting the current flow through an inductor (the
electromagnet), and the collapsing magnetic field induces a voltage
in the coil that increases until something breaks down - hopefully
(and normally) as a spark at the gap at the interrupter points and
not an as a damaging arc between winding layers inside the
electromagnet coil. Excessive voltage will lead to more frantic
clapper actuation and more arcing because the interrupted current is
higher with a higher voltage. You just want to achieve a reasonable
balance between reliable, pleasant sounding operation and minimal
arcing for longest contact life.

Don't worry. Hope this helps.

awright

How about using an optical relay? Wouldn't contact life be almost a non-issue, then?

- NRen2k5
 
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