Arduphono

I've had an old BT phone for a while now, and recently bought a cheap one in a market. I finally decided to put some time into converting it to stand-alone use, using an arduino. The result is in the video below.

The internals comprise an Arduino Uno and a 'Music Player' shield. There's also a prototyping shield with some custom circuitry on it.

The original dialler mechanism has two GPIO lines on the Uno attached to it, the code uses these to decode the numbers that are dialled. The 'on hook' switch is also attached to a GPIO line, this is used to detect 'on hook' or 'off hook' and put the code into one of two modes.

The bell solenoids have been rewired from their original series configuration and have been attached to a GPIO line each via some power transistors. 

The music shield is wired to the earpiece in the handset, this is used to play various tracks on an SD card inserted in the shield.

The two modes of operation are either 'on hook' which is when the phone delays and rings, and the 'off hook' mode which is when it waits for dialled numbers. 

Dialled numbers are commands to the phone:

112 moves to the next track on the SD card

2DR is a command that delays for D seconds in 'on hook' mode and then rings the bells for R cycles.

3DR is the same as 2DR except that the delay is in minutes not seconds.

The music player shield is frankly rubbish. It is  an MP3 player chip with GPIO lines wired to all the manual controls. There's no detection of the track being played and all you can do is turn it on and off and move to the next track. And adjust the volume. It barely works for the Arduphone. I have a long recording of a dialtone as the first track, so that is what you hear when you pick up the handset after turning the phone on. It does run out after a while, though, and will then move to the next track.

The ringing circuit was tricky as it is driven from a high voltage in the real phone environment. I had to drive a power transistor with four GPIO lines to get enough current to provide a kick to the clanger which would actually ring the bell. This area could be improved.

I think if I get round to doing a second version then I'll have to update the music shield, but this version is quite a lot of fun eveb with it's problems.