Issue with Bluetooth rotary phone project

Hello all,

What I am trying to do is make an Android device pair with an old 1950's Western Electrics rotary phone, similar to Sparkfun's discontinued model.

https://www.sparkfun.com/products/retired/8929

I need to be able to:

Dial and receive calls on the rotary phone, whenever the android is close enough to pair, just like a standard bluetooth headset.

I have an Elegoo Uno R3 and HC-05 connected together, and I am able to read data through the Serial monitor in the IDE coming from the Bluetooth terminal app on the Android. I am also able to read the dial through the serial monitor by connecting it to the arduino with jumpers and the library.

I am unsure of how to connect the Ground, power and two receiver wires coming from the headset to which pins on the Arduino.

I hope that makes sense as this is my first project and I have a very limited electronics background. I have googled extensively and found lots of wiring diagrams that show which wires are coming from the headset but none that explain how that can be translated to readable information by the arduino and sent through the HC-05 to a phone.

Thank you for any help and I hope I've provided enough information.

HC05 is not full duplex I see issues there already

What I am trying to do is make an Android device pair with an old 1950's Western Electrics rotary phone, similar to Sparkfun's discontinued model.

Can I just clarify, do you have a modern reproduction rotary phone similar to the Sparkfun one, or do you have an actual, vintage 1950s phone?

If the former, I'm sure someone here can help.

If the latter you might like to consider that Bluetooth wasn't even an idea in someone's head, let alone a working product in 1950.

Or am I missing something here?

It is an actual old phone.

Not sure what you mean, there are dozens of finished versions of what I am trying to build.

I am trying to replace all the old components with an Arduino, an HC-05 and possibly a new mic and ear piece if needed.

Sorry I didn't specify.

It is an actual old phone.

Then it didn't have Bluetooth when it was made.

Not sure what you mean, there are dozens of finished versions of what I am trying to build.

Then they must have been modified with modern circuitry added.

Wolframore,

Does that mean that the module can't communicate two ways at the same time?

If so, can I fix this with a different bluetooth module, or an audio shield of some kind I could attach to the handset?

yes full duplex means you can hear and talk at the same time. I would look into how bluetooth headsets with mics are made

I'll look into that thank you for the reply.

Are you trying to transfer audio using HC-05 and arduino?

Maybe post a wiring diagram of what you intend to do.

(Even if the diagram has fundamental flaws, it will give a better understanding of what you are trying to do, so don't be shy)

wolframore: HC05 is not full duplex I see issues there already

And the old phone handset has the carbon microphone and the electromagnetic ear piece in series so you can hear your voice a bit when you talk into the mike.

Paul

I remember taking those apart for my science fair project... dad didn't think that was so great :D

The HC05 bluetooth module operates on SPP (Serial Port Protocol) only, as far as I know. That is you can use it to transmit/receive serial data.

To transmit and receive audio signals via bluetooth you need a different type of bluetooth module.

See this bluetooth tutorial for information about the various protocols.

John, thanks for the reply

I am going to try a RN-52 module on a breakout board from Sparkfun. I am hoping to wire the handset of the old phone directly to the board.

I'd prefer to replace the microphone and speaker by modern equivalents, for starters. That'll save you quite some headaches.

The wire connecting to the phone having only two conductors is not a limitation: build all the electronics into the handset, and use the wire to the hand set to power the project.

The easiest way to do this would be if you can find a ready made Bluetooth device that has microphone and speaker built in. I don't really see a use for the Arduino or any microcontroller in this project, tbh.