This is my first post and also my first project with the arduino. I did a workshop so I understand the basics of the platform,
but I am new to this, so if you can help me clarify my thoughts or the feasibility of this it would be great!
I'm doing a theater play, and I wish to make 3 telephones ring, instead of using sound samples.
The 3 phones are of the rotary kind, with bells. In my research I've found out that the phones are fed with -48v of DC,
and the signaling is made with a more or less 105-volt RMS 20-Hertz sine wave. (from wikipedia) and that must be AC.
I live in Portugal, and we have 220v - 50Hz AC.
I must have a way to convert the 220v - 50hz AC to the 105-volts 20Hz
then have that go through 3 relays that would be controlled by the arduino.
Once I get the hardware part done I think I can solve the triggering, through software (Max/MSP, Ableton Live, APC40 etc..)
I've red a MAKE article on the garduino and I can adopt the schematic with the relay they have there which is simple enough.
But how do I make a 20Hz signal with 105Volts? do I use a transformer?
Can I use the output of a soundcard and generate the signal from there( :~ )?
And if do I need to have the -48v of DC or just hammer it with the ringing pulse?
Thanks in advance
Gonçalo Alegria
research links
gear/software i already have for this
Laptop -> ?
Arduino Duemilanove
Akai Apc40
M-Audio - Axiom 25
Ableton Live Intro
Max/MSP
you might be able to find the coil that rings the bell and rewind it with less turns of wire to be able to control it with lower voltage. then you could control it just like any other low voltage solenoid, just pulse it with whatever voltage you wind the coil for.
I don't know if the ringer would ring at 50hz with same pulse as with the 20Hz, I got a sample that I was studying and the ringing is in sync with an sinusoid LFO/VCO at 20Hz...
But I will be disassembling one of the phones tomorrow and test it with that option as well. (hopefully won't die)
You can make one of these with a simple step up transformer and H bridge.
If you get a 220V to 24V small mains transformer and drive the secondary of this like it was a motor with 5V and a H bridge at 20Hz then you will get enough out to ring your phone.
I made many of these in the 70s also as stage props.
I would advise you to also have an arrangement where you can bypass the receiver hook circuit because sometimes actors do not replace the receiver correctly and then it won't ring on the next cue.
I will try to use the arduino to do this. I have (want) to control the 3 phones. So the amp solution is not in anyway practical. I know I can have the arduino control at least 3 relays.
I do want it to be safe for the actor that is going to pick up the phones.
If I reduce the voltage with the resistor will it be safe for him in case something happens?
If can offer some advice based on our telephone system in NZ (and Britain).
The frequency just makes the ringing sound more urgent. (Ours was 32Hz from memory) The ringer is a pair of solenoids, ie mechanical, so it has limits.
It takes about 80-90v AC, but if you look, the bell mounting holes are not in the centre, so you can rotate them to optimise the ringing volume, based on the incoming ring voltage.
The bells are different, to give a dual tone effect
A simple step up crude oscillator driving through a 50 or 60 hz mains transformer will be fine. Because you can't generate much power, there should be no need for a resistor.
If you make 3, and have them connected seperately to each phone, then you use the arduino to do the ringing sequence. Which may include having more than one ring at the same time (for future)
Party lines in NZ used a different ring sequence to identify who it was for. one ring pause one ring = x, or two rings pause two rings = y etc.
The phone line is 48v DC, and the exchange detected the phone being picked up by, and operated a relay. This made the ringing stop, so that you didn't get an earful of ringing noise.
You can use the switch connected to the lever under the handset to disconnect the bells, otherwise you need to train the actor to wait until it stops ringing...not a natural thing to do waiting until the noise stops to pick it up.
Grumpy_Mike:
You can make one of these with a simple step up transformer and H bridge.
If you get a 220V to 24V small mains transformer and drive the secondary of this like it was a motor with 5V and a H bridge at 20Hz then you will get enough out to ring your phone.
I made many of these in the 70s also as stage props.
I would advise you to also have an arrangement where you can bypass the receiver hook circuit because sometimes actors do not replace the receiver correctly and then it won't ring on the next cue.
This is an old thread but the information given by Grumpy_Mike was exactly what I needed!
With this information it was just straight forward to make a "wireless" analog telephone for the stage that can ring as needed.
Thank you!
(hopefully won't die)