Arduino Fruit Machine - LED Displays

I bought an old fruit machine (slot machine) from eBay and stripped it down into separate components.
In this video, I'll show you how to use the 1.8" 7-segment common cathode LED displays (http://www.farnell.com/datasheets/99300.pdf), which were used to display the cash payout value at the top of the machine. Using a handful of cheap components, it takes just three GPIO pins on the Arduino to control these LEDs to display any value you want.

These are nice big, bright displays but, since they have a forward voltage of 5.55V, they can't be powered by simply writing a digitalWrite(HIGH) from an Arduino pin. Instead, I'll be using two transistor array chips:
- A UDN2981 will act as a current *source* to the anodes of the appropriate segments
- A ULN2803 will provide a current *sink* from the common cathodes of each display

The outputs on these two chips will be set by two, daisy-chained 74HC595 shift registers. Using just three pins on the Arduino (latch, clock, and data), a single byte value will be sent to each register, where the '1' bits in the first byte determine the display cathodes to connect to ground, and the '1' bits in the second byte determine the segment anodes to connect to the 12V current source. By iterating over the displays quickly and setting the appropriate segments on/off in sequence ("multiplexing"), persistence of vision will make it possible to display any value across the displays.

Download the wiring diagram and the Arduino code from: https://github.com/playfultechnology/arduino-fruitmachine

For more projects, please check out https://www.patreon.com/playfultech

Видео Arduino Fruit Machine - LED Displays канала Playful Technology