90 vdc 25 cps Oscilator

Question

I have a Question, I want to test my telephone bell for loudness, I understand that the bell rings on 90 VAC 25hz, or 25 cycles per second. I would like to buid a simple Full, sign wave Oscelator that will put out 90 VAC at 25 CPS. so I can test the bell. I want it to be solid state.. using house curent, not a battary. Thank you Richard scott my email > r172scott@hotmail.com 
 Attachments:

jvdberg@ieee.org · Accepted Answer

To create a 90 VAC 25hz signal for telephone bells can easily be accomplished using a sine wave generator, a 5 Watt audio amplifier and a step up transformer. Because the frequency is lower than the mains frequency, the transformer needs more turns than a 60 Hz transformer. A transformer designed with a primary winding for 230V and a secondary winding for 12V could be used to step up the 5Volt 25Hz from the audio amplifier to 90 VAC. For the sine wave generator you can use a standard test instrument or build a wien bridge or RC generator. The volume control of the amplifier can be used to set the output voltage to the desired value. If the frequency of the oscillator is variable, you can change both frequency and amplitude to test the behavior of the telephone bell.

shabaz · Answer

Hi Richard, (Presuming there is some reason not to plug the bell into a phone line to test the loudness (assuming it is approved): This site is great for information on what you need, down the page it provides details of the frequency and voltage to expect (it won't be exactly 90V, it could be far lower, and the frequency is different depending on country). Also, for modern phones the frequency won't make a difference, you could just use a mains transformer and use 50/60Hz. It will only affect mechanical bells. Anyway, that site refers you to an astable multivibrator which would then need to be powered by DC which you can derive from your house supply using a power supply. The astable freq calculations are on Wikipedia if you'd like 25Hz.