A simple traffic light implemented using ATTINY85. Lights cycle between configurations and user can move to the next one by pressing a button.
I used big, 10 mm LEDs. The green one has ~3.15V forward voltage and thus the second battery. You don't need it for regular LEDs.
BOM:
- ATTINY85 in DIP package;
- 8-leg DIP socket;
- 10 mm LEDs: red, yellow, green;
- 1k, 1k, 330 ohm resistors;
- tactile switch with a pull-up resistor;
- an ON-OFF switch;
- 2x CR2032 battery;
- 20 mm wide PCB.
Consists of multiple parts for 3D printing in PLA. Print with 20% infill, without supports. See case/ for Fusion 360 files and exported STLs.
I wanted to make ATTINY85 replaceable and over-engineered a bit.
Case Assembly BOM:
- 2x M2.5x20 flat-head screw (DIN 965);
- 4x M2x12 flat-head screw (DIN 965);
- 4x M2 hex nuts;
- 2x M2.5 threaded insert, height up to 10 mm (goes into the base);
- 2x M2 threaded insert, height up to 6 mm (goes into the lights back);
- 2x office clip 🙂 (cut and bend to make CR2032 contacts).
The code is a PlatformIO project. It basically cycles between states after a timeout. The states are as follows, with possible actions marked with colors:
User can manually move to the next state by pressing a button (the red cycle).
μC will enter deep sleep after 10 minutes since last button press.
The light runs on a single CR2032 cell capacity (about 220 mAh), so it should consume minimal amounts of energy. Current optimizations are:
- Deep sleep after 10 minutes (commit 0f1c727)
- Disabled ADC (commit dee5303, blog post)
- Unused pins set to
LOW(commit dee5303, forum post) - Custom fuses settings (commit 2d93b48, fuse calculator)
- disabled Brown-Out Detection which does some voltage comparisons
- 1 MHz clock speed from diving 8 MHz by 8
Remember to set fuses from PlatformIO! It doesn't happen automatically during upload.