Electrical Puzzle!

[jeraldo]

I have an old French bell, probably a doorbell or phone bell extension. It has a striker and two bells working off 2 x 500 ohm things (resistors?). I'd like to know what voltage it would take to make it work. The connection is via two exterior metal terminals so it clearly won't be a big voltage. I tried a 9v battery which moved the striker one way or another depending on the + and - connection, but it stopped and wouldn't continue moving left and right to ring the bells continuously. Any thoughts? Would like to wire it up to my doorbell which works of a voltage reducer but don't want to do anything remotely dangerous!

[bhg481]

It sounds like you need an AC power supply for it because of the reaction when you used DC from a battery.
There are bell transformers on Amazon, some of which are multi output voltage. If 9V moved the striker enough to ding the bell I'd go for a 4/8/12V output transformer and see which voltage is best.

http://www.amazon.co.uk/s/ref=nb_sb_ss_i_1_8?url=search-alias%3Daps&field-keywords=wireless%20doorbells&sprefix=doorbell%2Caps%2C329

[jeraldo]

Thank you Mark. I've just connected it to the output on the existing (quite old) transformer and it rang permanently! I assume it's because one wire comes out of the transformer to the bell and one goes direct to the bell from the push with the other going from the transformer to the supply. I might be able to figure it out now but your guess at 12v looks right to me! Many thanks again.

[bhg481]

What you need to have is one wire from the output of the transformer to the bell, one from the other terminal on the bell to the bell-push and one from the other terminal on the bell-push to the second output terminal on the transformer. When you press the bell-push the bell should ring and then stop again when you release the bell-push.