Using an electric bell

[jeraldo]

Hi. I have an old French telephone bell which has two terminals on the outside then some stuff on the inside which are presumably coils of some kind. You can tell I'm not technical! The only clue is that it is 500 ohms. My question is - can I use this as a doorbell passing a small current from batteries through it? If not, would I need to by-pass the gubbins inside somehow? It's so nice an item, it really begs to be used practically. Any help appreciated.

[Graham-W]

It's probably like this http://www.gcsescience.com/pme6.htm
Try putting 6 volts across the terminals and see what happens. You may have to clean the contacts inside and also they sometimes the contacts need adjustment.

[beso]

Old telphones used quite high voltages to ring,

The energy to run the bell was provided by a small generator wound by a handle.The high resistance would also suggest a reasonably high voltage device. I doubt it will work on batteries.

[jeraldo]

Thanks both of you. I'll give it a go. Might be able to sort something out!

[Buenchico]

Many early bells worked by passing an ALTERNATING current around one or more coils. The magnetising effect would then alternately attract and repel a metal bar, which struck the bell, thus making it ring.

I suspect that passing a DIRECT current (from a battery) across the terminal won't make the bell work but (as long as you keep to a low voltage) there's no harm in trying.

Chris

[beso]

Yes, The little generators were AC and a substantial voltage. You would not want to touch the ringing current.

With DC you will normally just get one bing.

[heathfield]

Phone ringing voltages are normally between 50v and 80v, varying from 20Hz (USA) to 60Hz (Parts of Europe). Getting a transformer that would provide these levels of voltage from UK mains might prove tricky. There's also the safety aspect; if you were to hook up a push-button on your front door, and the insulation failed - well, getting a shock from ringing voltages isn't much fun! (Personal experience).