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Ancient (school) electric bell

Discussion in 'General Electronics Discussion' started by basham, Oct 8, 2011.

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  1. basham

    basham

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    Oct 8, 2011
    I have just acquired an ancient electric bell in France, which may have come from a school or lycée. The cast bronze bell is 15 cms tall and slender, a bit like a cow bell, and the heavy duty cast iron case has the letters CBD cast into it. However, the bit which is really foxing me is the power supply. The man I bought it from appeared to know little or nothing about it, and told me that the twin and earth cable attached was for a normal 220V supply. I tried connecting it to the mains and it immediately tripped out the entire electricity supply to the house.
    A look inside the case elicits the following information. The incoming supply is connected to what appears to be a capacitor, which is marked T.E. 650 V - 12/48. This means nothing to me but might give someone cleverer than me (almost anyone) a clue as to the required power supply. The other clue is that the electromagnet has twin coils, each carefully labelled with a 50. The early power supply in France was 120 V in some parts, but the bell could even have worked on direct current from batteries I suppose.
    Any helpful information or suggestions would be much appreciated.
     
  2. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    old bell

    Hi basham.
    I have some idea, but another member more experienced than me probably could take it further.

    Any way you mention twin and earth, does that connect to a transformer in the bell unit, or does the cable connect at all, the capacitor marked TE 650 V 12/48 sure has me baffled, is it a can type capacitor, be it an old card or board type casing, or is it a different type / shape of capacitor, energized electromagnetic installations are normally mains direct, or stepped down, is there a circuit board in there connections etc. A picture or two would give some more detail, the 50 you mention could be the coils property's, resistance maybe, DC power is common to the coils, is there diodes or a rectifier. Lots of questions,

    Some pictures would help, i dont know if another member out there can elaborate further on just your description, maybe.
    Dave. :)
     
  3. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    Possible but unlikely that it is a telephone bell. The telephone system puts out an AC signal through a capacitor to ring the bell.

    If it is a DC bell, then there will be a contact to interrupt the current as the bell vibrates.

    What tripped the supply? I doubt if it could trip the entire house due to overcurrent. It more likely that it tripped due to earth leakage. Check the resistance between the power leads and the earth wire, any connection at all means the insulation is faulty. This should preferably be done at high voltage but an ordinary meter may give some indication.

    Measure the resistance between the power wires, this may give some indication of the working voltage.

    Duke
     
  4. basham

    basham

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    Oct 8, 2011
    Thank you for the replies. There are, in fact, contact points which I didn't mention, simply because I didn't realise they were significant. What I take to be a capacitor is about 5 cms square and about 1 cm thick. Presumably the presence of the contact points means that it was DC powered, probably through a mains transformer. I'll try to organise a photo shortly.
     
  5. basham

    basham

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    Oct 8, 2011
    [​IMG]
    Further to my ancient school bell thread, herewith a link to a photo.
     
  6. davelectronic

    davelectronic

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    12
    Dec 13, 2010
    Your link does not work.
    Dave. :)
     
  7. duke37

    duke37

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    771
    Jan 9, 2011
    If the bell has contacts it was probably run on batteries, perhaps as low as 2V. The capacitor is there to reduce the sparking of the contacts.

    In your reply, Go Advanced and attach the photo directly. This saves everyone time and effort.

    Duke
     
  8. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    Whats the twin and earth for, dont think charging circuits existed in the old days, although i might be wrong, i would like to see the bell it sounds interesting.
    Dave. :)
     
  9. basham

    basham

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    Oct 8, 2011
    I'm afraid I'm struggling to attach my photo. What exactly do you mean by Go Advanced?
     
  10. davelectronic

    davelectronic

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    Dec 13, 2010
    You could upload a picture using an on line application like photo bucket, you upload from your pc files the picture you want, it goes in an online album, then you copy and paste the IMG code. I will post a link to photo bucket. And a picture example from my files.
    Dave. :)

    [​IMG]

    http://photobucket.com/
     
  11. basham

    basham

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    Oct 8, 2011
    I'm probably being incredibly thick because I still can't quite see how I can get the image in my Picasa web album to appear like the image Dave has posted, but the link below does appear to work.
    [​IMG]
     
  12. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    Electric bell

    There is no link i can see, i had one or two problems when i wanted to start uploading images. Ive also got picasa, but its easier to upload a picture from an online app. There is photo bucket, and another could image shack, ive never uploaded straight from my pc to the forum, if you join photo bucket you can upload the images to that site, they give you options for a code link, for uploads of the picture to web sites forums etc, i copy the IMG code for the pictures address destination and post it.
    Dave.
     
  13. basham

    basham

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    Oct 8, 2011
    Ok. Thanks. It looks like joining photobucket is my best option. But just in case it works this time I'll try attaching the picasa link again..[​IMG]
     
  14. duke37

    duke37

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    771
    Jan 9, 2011
    All I get is a little red cross which does nothing.
    At the bottom of the message you type in you have the option of 'post quick reply' or 'go advanced'.
    In 'go advanced' you can click on a paper clip and attach a photo from your computer or elsewhere.
     
  15. basham

    basham

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    Oct 8, 2011
    First attempt at a photobucket link. [​IMG][/IMG]
     
  16. basham

    basham

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    Oct 8, 2011
    Looks like it didn't work. Why is it that when I type my reply the link appears in full, but when I post the reply the link disappears and becomes a box with a red cross in it? Any ideas?
     
  17. basham

    basham

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    Oct 8, 2011
    Herewith another attempt at attachment DSC00029.JPG
     
  18. duke37

    duke37

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    Jan 9, 2011
    That's better.
    The capacitor seems to be connected across the input to reduce interference.
    The coil wire looks to be quite fine so the operating voltage is not likely to be very low.
    The bell can run on DC and perhaps AC.
    The voltage necessary needs to be determined experimentally.
    The wire colours are the standard european mains colours, this does not mean that it was ever connected to the mains.

    Duke
     
  19. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    Electric bell

    I agree on the wiring being European standard, but i cant see a capacitor in the picture, not a problem, i would measure the coils resistance, there seems to be a solder join in the green coil wires, and its not covered or insulated from the case.

    This again may have no bearing on the working of the unit, i cant see a step down transformer anywhere, but that could have been in another location, lots of variables, the cable thickness and wiring would lead me to believe its mains wired, but if its tripped out your RCD MCB i would not reconnect to the mains.

    There are what looks like to brass adjusters with locking nuts, or thats what they look like, if the mechanical movement is stuck, and i dont know if it is, then it would draw larger currents and possibility trip your mains supply out.

    The only other reason for tripping the MCB is an earth fault, or damaged coils, have a sniff, i am not joking burnt electronics smells can linger for ages, measure the coils resistance, as there wired.

    Then use the buzzer on the casing, its metal of course try to find an earth fault ( part of the circuit coming in contact with the casing.

    Another possibility is what or how is the earthing of the french supply work, different to ours i dont know, something to look at.

    Neutral is still part of the power circuit, but on the return to the supply lines. you might have to isolate neutral and earth, depending on how the circuit is wired, never try to power it with no earth attached.
    Dave. :)
    PS, look closely at the live connection and use a meters continuity between live brown wire, and green and yellow wire earth. if the buzzer sounds part of the live circuit is going to ground and the case / chassis exterior.
     
    Last edited: Oct 10, 2011
  20. duke37

    duke37

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    771
    Jan 9, 2011
    I assume that the metal box on the left is a capacitor. A blue wire semms to go towards the blue inout wire and the brown input wire has an extension under the blue wire presumably to another connection on the capacitor.

    Capacitor value and voltage rating would be interesting.
     
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