Laser Sign

Use some lasers to write on the wall!

You need:

8 laser leds (you can buy them for 4 euros here).

two-coil stepper motor

small mirror

arduino nano

4 power NPN transistors, 4 power PNP transistors, 8 1k resistors. Wires

support

Build a dual H bridge, using the above schematics, which I obtained from here. (Thanks Kerry Wong!)

Connect 8 of the lasers to the arduino (1 i/o pin for each laser) and fix them to something solid (I used a scrap PCB).

Mount everything on some support (I used an old ethernet switch).

Here is the code I used. At the very least you should assign the correct pins you used to connect the lasers and the hbridge.

You can control it with an android phone using an OTG cable (you can build one yourself using the above schematics from here) and a serial terminal app (I’m using this one). Set the speed to 9600. Whatever you type in the app will be echoed on the wall.