Arduino Powered Writing Telegraph

This is an Arduino powered short of writing robot that writes string of text on a strip of paper. The idea for this came to me from a pretty old article (linked here) (though only in Russian). I love this as the ways it write using dots gives the retro feeling and it's so satisfying. The main article suggests servo motor to move the pen, but I have lots of L293d drives and some stepper motors from old DVDs drivers,So I modify a bit to make it work for me.

• arduino (nano/pro mini) smaller is better for portability
• A solenoid
• A transistor (like bc547)
• stepper motor and drivers (also need the linear rails from DVD drivers)
• wood, I have used woof for the encloser, you can 3D print, or a transparent acrylic one will look cool
• HC-5 /6 bluetooth module
• A switch to act as limit switch (with lower actuation force )
• soldering supplies
• A type-C female port for power

First create a Rectangle using wood and glue, this will be base for out x axis, mount two piece of wood to each side as standoffs for guiding rails, glue a base for the stepper motor beside these standoffs and add connect the sliding parts to the stepper motor, a rigid piece of wire can also be used to slide on stepper motor.

For moving the paper, I am using two rubber circular "things", those are rotated directly by the shaft of stepper motor. The paper slides in b/w those two-circular thingy. One thing to pay attention here is to avoid any oil or grease on all of these parts. Clean the stepper motor with alcohol as it has some short of lubricant on the shaft.

The connections are simple, just two stepper drivers, and a solenoid and the
Bluetooth module. Take a look at attached pic of the circuit diagram. Make sure that you code works fine before soldering the Rx and Tx pins to Arduino. Don't forget the limit switch.

You can check the code by intentionally calling printString() method in setup(), the code has commented line.

You can get the code and the android app to use the telegraph from my github page. Install the app on your android smartphone. You can also change the name of your Bluetooth module using AT commands to give more personalised touch, google it to know more.

This step is all about aesthetics, close the sides of the encloser (I have used cardboard), oil the wood and also grease the linear rails. The position of solenoid is litter hard to setup, it’s all about try and error.

And yeah, you would probably have a working telegraph, if any problem persist comment section is open, use it to the fullest:)