- 5x LED i2c Backpack
- 6x Jumper Wire - 0.1", 4-PIN, 12"
- Laser module
- Light Sensor
- 1x Arduino
20 Male headers pins, for i2c connector block
- 6x AA rechargable batters
- 1x Battery Holder for 6 AA Batteries
- 9v connector clip (tinned ends)
- Mini Breadboard
- Wire for connecting sensor, laser and wiring harness to the breadboard
- Black electrical tape to hold wiring harness pin headers together
- 3D printed or laser cut structure
~6v to the Arduino VIN pin and the LED backpack, using the breadboard
The LED backpacks have uniqie i2c addresses set (70-74) using solder on the back.
Any backpack compatible with the Adafruit library should be ok, check voltages!
The headers pins are split into 6 pin segments and then every pin on every individual segment is joined together using solder. The harness connects the +V, GND, SDA & SDC from the Arduino to all the LED backpacks in parallel.
This wiring diagram is as viewed from behind the lap timer, left to right order is important (see below):
- Connect SCL (yellow) to the I2C clock - on Arduino UNO thats Analog #5, on the Leonardo its Digital #3, on the Mega its digital #21
- Connect SDA (green) to the I2C data - on Arduino UNO thats Analog #4, on the Leonardo its Digital #2, on the Mega its digital #20
- Connect GND (black) to common ground (i.e. battery and Arduino)
- Connect VCC+ (red) to power - 5V is best but 3V also seems to work for 3V micro controllers.
The light blue/cyan blobs represent where solder needs to be applied to bridge the connections in order to set the I2C address, this is where the order is important, if this is back to front the numbers of the laptime will be displayed in reverse order.
Please install the 2 Adafruit libraries required by following the instructions here
The sketch can be found here.
It has some wiring information and also information relating to which pins, on different types of Arduino's, map to interrupt numbers in software.
The Arduino Sketch uses an interrupt handler triggered by pin voltage change to detect the break in the laser beam.