by Theo Demetriades
Project Overview
This project uses an Arduino Uno to control a row of 6 LEDs on a waving wand to display letters. Columns of the letter are flashed in quick succession to create the illusion that the parts of the image appear at the same instant.
Tools and Materials
- Arduino Uno
- Prototyping board
- 3D Printer
- Soldering iron
- Wire
- 430 and 10k ohm resistors
- 100nF capacitor
- 595 shift register
- A3144 Hall effect sensor
- Small magnet
- Plastic ruler
- Duct tape
- Hot glue gun
- Wooden dowel rod
Step-by-Step Instructions
3D print casing for LEDs and Hall sensor.
Solder LEDs and Hall sensor to 9 ends of a ribbon cable. Each LED needs its own wire for its anode, but their cathodes are soldered to a single ground rail. The Hall Sensor needs leg 1 soldered to a wire connected to +5V, leg 2 soldered to the common ground, and leg 3 soldered to another separate wire to be connected to the input pin of the Arduino microcontroller. After soldering the individual wires, use a hot glue gun to insert the LEDs and Hall sensor into the casing, then solder the common ground rail.
Use duct tape to attach the casing to the top of a plastic ruler. Attach the small magnet to the end of the wooden dowel rod and tape the rod to the ruler with some spacing in-between.
Use a pluggable terminal block to connect the ends of the ribbon cable to the prototyping board.
Build the circuit from the circuit diagram on the prototyping board. Each of the first six outputs from the 595 shift register are passed to a 430 ohm resister before being connected to one of the wires controlling an LED. A pull-up resistor is used for the Hall effect sensor, meaning it output a high signal by default, and flip low when triggered. The capacitor is used to filter output noise.
Connect the Arduino Uno to your PC, and upload the sketch. Wave the plastic ruler back and forth such that the hall sensor passes the magnet near the middle of its swing. Adjust timing variables as needed.
