'Stay Safe' LED display (created in response to Covid-19).
- 1 x 5mm DC Jack socket
- 1 x L7805CV 5V voltage regulator
- 1 x 10µF electrolytic capacitor
- 1 x 100µF electrolytic capacitor
- 1 x Ardiuno Nano ATmega168 5V 16MHz
- 1 x Momentary switch / push button
- 1 x 10KΩ resistor
- 1 x ULN2803A Darlington Array
- 1 x Piezo buzzer
- 3 x 1x3 headers
- 1 x 1x2 headers
- 7 x 4608X-102-331LF resistor network ( each with 4 x 330Ω elements)
- 39 x 3mm yellow LED
- 39 x 3mm green LED
- The system is powered via a 12V power supply which is connected to pins 1 and 2 of the 5V regulator (U1) via the 1x2 header block.
- A 100µF electrolytic capacitor is connected across the input of Q1, and 10µF electrolytic capacitor is connected across its output.
- VIN of the arduino is is connected to the output of Q1 (pin 3), and ground.
- The buzzer is connected to D6 of the arduno, and ground.
- The push button is connected between D2 of the arduino and 5v (U1 pin 3). D2 also has a 10KΩ pull-down resistor to ground.
- D8 and D9 of the arduino connect to input pins 1 and 3 of the darlington transistor IC (Q1).
- Q1 com pin connects to 12V. Q3 gnd pin connects to ground.
- Q1 outputs are pin 2 (stay LEDs) and pin 4 (safe LEDs) and these are connected to the first 2 pins of a 1x3 header, with 12V connected to the 3rd.
- Stay LEDs are connected 13P3S formation, each chain running through a 330Ω resistor. +ve connection to 12V (via header block).
- Safe LEDs the same.
- -ve connection of Stay LEDs is to pin 2 of Q3 (via header block).
- -ve connection of Safe LEDs is to pin 4 of Q3 (via header block).
Download the following code and upload it to the Arduino:
https://github.com/alicraigmile/stay-safe/tree/master/src/stay-safe
See https://www.arduino.cc/en/Guide/ArduinoNano#toc5
My arduino was a clone and so I needed drivers for the USB serial interface - https://github.com/adrianmihalko/ch340g-ch34g-ch34x-mac-os-x-driver
Power it up and watch the display.
Pushing the button changes between 3 patterns. The buzzer will sound to tell you which pattern is active.
'Stay safe' is inspired by the work of so many - from local and national government, the NHS, emergency services and further afield - who looked out for us during the Covid-19 pandemic.