The trainer is based around an Atmel AVR ATtiny48 connected to 8 LEDs via 74HC595 shift register. The MCU can blink the LEDs in a timed pattern, or interface with additional hardware (buttons, sensors, etc.) All of MCU pins are broken out to headers, and all of the '595 pins can be controlled by software including PWM of the '595 output enable for dimming.
The board includes several surface mount footprints:
- SO-16 (1mm pitch)
- TQFP-32 (0.8mm pitch)
- 0805 (80x50 mil)
- 1206 (120x60 mil)
Also included are a DC power jack for 5V in and breakout headers for power and ICSP.
Workarounds: The regulator isn't needed if the input supply is suitably regulated (e.g. 5V).
- Do nothing. The regulator will be reverse biased and pass current through a diode drop.
- Bridge pins 1 and 2 of P4. This bypasses the regulator and the reverse protection diode.
- Bridge pins 2 and 3 of U2. This bypasses the regulator but keeps the diode.
Bill of materials
- (1) 2mm DC power jack
- (1) Atmel ATtiny48-A
- (1) Microchip MCP1700T3302E/TT 3.3v regulator
- (1) NXP 74HC595D-Q100 shift register
- (1) 1206 0.5A schottky diode (AVX SD1206S040S0R5 or similar)
- (2) 0.1uF 0805 capacitors
- (2) 1.0uF 0805 capacitors
- (8) 1kOhm 0805 capacitors
- (8) LED 0805 SMT (OSRAM LG R971-KN-1 or similar)
- (1) 3x2 ICSP male header
- Optional: (1) 1x4 header for power breakout
- Optional: (4) 1x8 header for ATtiny48 breakouts