🥇Cordless phone made from cans

A new take on an old toy, the tin can cordless phone takes last year's technology and pushes it into the present!

Just yesterday I was having a serious phone conversation, when suddenly my banana phone stopped working! I got very upset. Well, that's it - the last time I miss a call because of this stupid phone! (Looking back, I have to admit that I was probably too angry at the time.)

It's time for updates. And here it is - a new cordless phone from a tin can! A new, improved pseudo phone for all my communication needs!

Jokes aside, the project is really working. And here's how I made it.

Tools and materials

For the project, you will need quite a few electronic components and a couple of tools.

Tools:

Drill.
Metal scissors.
Hot glue gun.
Round nose pliers.
Hammer with a round head.

Materials (all in duplicate):

DFduino Uno R3
Gravity IO Expansion Shield (not necessary)
Analog sound sensor (microphone)
386AMP Audio Amplifier (speaker)
Battery compartment 6AA Battery Holder with round DC Barrel Jack (and 6x AA batteries)
NRF24L01+PA+LNA with antenna.
Push button.
Aluminum coffee can.
Connecting wires.

Preparing banks

Before connecting the electronics, you need to prepare the banks. We drill two holes in them - one for the antenna, the second for the button.

I started with the hole for the antenna. To begin with, I put the antenna board inside the can to measure how far from the wall the hole should be. I then marked out the spot for the hole with an erasable marker because I wanted to remove it after work. Then, with a tap, I marked out a place for the future hole. This will help drill in the next step.

The hole size will depend on the antenna you are using. I just matched the drill to the size, comparing it with the size of the thread where the antenna is wound.

I got 5,5 mm.

OK, put on safety goggles!

Having picked up the diameter and marking the hole, drill it. It is better to do this at high speed, but do not press hard. Tin is thin and tends to burr - be careful with sharp metal. Use metal shears and round nose pliers to trim the edge.

After that, you can proceed to the hole for the button. With him, things are a little different.

I work with what I have, so I decided to try again to make a hole with a drill and round nose pliers. But it would be much more convenient to do this with a Forstner drill. Here's how I did it.

First, I unscrewed the plastic nut from the button. Then I placed the nut where I needed to make the hole and marked its inner diameter. Then I drilled five holes and used scissors to remove the material and make the hole look round.

After that, with the help of a hammer and round-nose pliers, I hammered the edges inward and bent them - see photo. I recommend using a hammer with a round face. I used the regular one because there is no other.

Now you can screw in the antenna and button. Beware of sharp metal edges!

Hot melt time

It's time to glue all the components. First, turn on the glue gun and let it warm up. Then use glue to stick the antenna board to the jar. I also advise you to cover the metal part of the antenna sticking out with glue so that it does not short out with the can.

I recommend using as much glue as possible so that nothing is short on the jar. If you hear a crackling or squeaking sound during the test, something is probably in contact with the can.

Glue the Arduino Uno to the bottom of the jar and then connect the batteries. This is the most difficult part - I recommend applying glue to the edges, and then placing it so that the antenna looks up and the batteries are in the opposite part of the can. Batteries will be the natural center of gravity.

I glued the speaker on one side of the battery holder, and the microphone on the other. The reasons are aesthetic considerations and the desire to neatly lay the wires.

We connect electronics

When everything is firmly glued, it's time to connect the wires. Wire the components according to the diagram. Below is a list of connected contacts.

Antenna board:

MI -> MISO
MO -> MOSI
SCK -> SCK
CE -> Pin 7
CSE -> Pin 8
GND -> GND
5V -> 5V

Comment: NRF24L01 is a great thing, but it is very sensitive to nutrition. Connect it to 3,3V only - unless you're using an add-on board like I did. Connect to 5 V only with an additional board, otherwise burn the antenna.

Analog sound sensor:

Gravity Pins -> A0

Audio amplifier:

+ (speaker input) -> 9 or 10 (left or right channel)
- (speaker input) -> GND
Gravity pins -> D0

Switch:

NO -> A1
COM -> GND

A brief explanation of how the circuit works.

We use the library RF24Audio, so the microphone, speaker, switch and antenna must be connected in a strictly defined way:

The signal pin of the microphone always goes to pin A0.
Switch (reception / transmission) - on A1.
The audio amplifier can be turned on anywhere, the main thing is that it has power. The audio cable must be connected to pins 9 and 10.
Antenna pins CE and CSE are connected to pins 7 and 8 only.

Uploading the code

thanks RF24Audio library the program is extremely simple. Literally 10 lines of code. Take a look:

    //Include Libraries
    #include <RF24.h>
    #include <SPI.h>
    #include <RF24Audio.h>

    RF24 radio(7,8);    // Радио использует контакты 7 (CE), 8 (CS).
    RF24Audio rfAudio(radio,1); // Аудио использует радио, номер радио назначить 0. 
         void setup() {        rfAudio.begin();    // Инициализировать библиотеку.
    }

To upload the code, you need to install the Arduino IDE, download this code and open it. Make sure the programmer is set to AVR ISP in the tools menu and the board is set to Arduino UNO. Make sure you have selected the correct COM port.

Now connect the Arduino and the computer with a USB cable, and click the "upload" button on the top left. The code should load and you should hear a soft buzzing sound.

Try pressing the button and listen to see if the pitch of the buzzing sound has changed. At the top of the IO Expansion HAT board, the LED should turn off.

If so, then the program is working and everything is connected correctly.

Can testing

To check, you need to turn on both banks. Press the button on one of the cans and say something into the microphone. Do you hear sound from another can? Try this with another jar.

If the sound passes, then you have succeeded! If you have interference problems or hear buzzing, check for grounding problems. I can recommend wrapping the antenna with electrical tape.

After that, test the range of work - if there is nothing in the way of the signal, it should go for a distance of about a kilometer!

Conclusion

Congratulations, you've made it to the end of the project! Great job!

Source: habr.com

Cordless phone made from cans