Prop Phone Ringer - Page 1
Forum section: electronics / beginners

author: PoLoMoTo
author_rank: Newbie
timestamp: November 10, 2013, 12:07:55 am
content: So I'm trying to make a circuit to make a phone ring and ideally stop ringing when the handset is picked up.I put to together this circuit:http://www.techlib.com/electronics/telephone.htmlI'll attach my Element14 parts list as soon as the site comes back up...But it only seems to power the phone because I can hear myself blowing into the mic but it doesn't ring. I think the problem is being caused be something on the first inverter, all of the others are reading + or - 12v except for that one which is fluctuating between 5-15v. The output to the phone is 12v no fluctuating at all.I'm also kinda confused with the transformer I got, a Hammond Manufacturing 166G9,http://www.mouser.com/ds/2/177/5c0018-19-57926.pdf, it has three wires on one side that I don't really know what to do with and the data sheet mentions a rectifier so I'm not sure if that means its built in or not.Thanks in advance for your assistance.

author: clockbiscuit
author_rank: Contributor
timestamp: November 10, 2013, 10:36:00 am
content: Very interesting. This circuit may be more complicated than it needs to be as you don't require anything to be done with the audio into or out of the phone. Its my understanding a high voltage is used for the phone ring signal (likely because back in the day it was electrically demanding for phones powered from the phone line directly). Unfortunately I am not totally familiar with the logistics of this and just what that signal should be. What can you measure on the output of your circuit when you are trying to make the phone ring? 12v DC?

author: Jon86
author_rank: Frequent Contributor
timestamp: November 10, 2013, 10:51:19 am
content: The third output is going to be a negative voltage, just use two wires off the transformer, the middle and left or right.There's never a rectifier built in, if you need one you'll have to put it in.

author: Stonent
author_rank: Super Contributor
timestamp: November 10, 2013, 11:00:55 am
content: Stick an old cell phone inside a real phone and wire the receiver button to hit the end button. Load a ringtone that sounds like a real phone on it.

author: Psi
author_rank: Super Contributor
timestamp: November 10, 2013, 11:11:30 am
content: Quote from: Stonent on November 10, 2013, 11:00:55 am+1

author: SeanB
author_rank: Super Contributor
timestamp: November 10, 2013, 11:26:40 am
content: Just make the cadence circuit by itself and see if it runs, then use the detector you have to drive a NPN transistr which drives a PNP that disconnects power to the 4069 inverter. Most likely the inverters are not running because of leakage through the board because of either components leaking or flux residues causing unwanted currents. Bigger value film capacitors and lower value resistors will make the oscillator more stable, along with proper board cleaning.You need the right cadence frequency and the ring frequency needs to be 25Hz. In old phone offices this was made with a ring of 3 relays with RC delays on the coils to get the right frequency.

author: dfmischler
author_rank: Frequent Contributor
timestamp: November 10, 2013, 11:56:08 am
content: And old phone ringers in the USA expected to see around 90 V RMS at 20 Hz.Telephone ringing circuitsRing Voltage Tech Bulletin

author: G7PSK
author_rank: Super Contributor
timestamp: November 10, 2013, 04:35:43 pm
content: Telephone ring circuits require around 90 volts in the uk as well with a minimum of around 40 volts required at the phone. It's usually around 20 to 25 HZ as well