“An automatic pencil sharpener machine that works using linear motion. You can sharpen any pencil just by pressing a button and it will take care of the rest, including gathering up all the rubbish into a container.
Components
- Attiny84, for the micro-controller.
- Nema 17 stepper motor, to drive the linear motion.
- A4988 stepper motor driver, with 100µF-1000µF capacitor across the motor power pins.
- 12V power supply, with at least 3A max rated current.
- LM2596 DC-DC step up/down converter, to convert 12V to 5V. 12V is required for the motors, 5V for the micro-controller.
- MCP1700, 5V voltage regulator, to ensure the Attiny84 has a consistent and smooth voltage. 1000/100µF and 100,000pF capacitors are soldered directly on the MCP1700 to deal with voltage spikes.
- 12V DC motor, the one used has a max speed of 500 RPM.
- IRF3708 MOSFET, to be able to control the DC motor using a micro-controller.
- 1N4004 Diode, to be placed across the DC motor to prevent negative voltage spikes if the DC motor is rotated when the circuit is off.
- Sliding switch, as an on and off switch.
- 2 buttons, to control the stepper motor, left and right controls.
- 8mm L30cm lead screw, for the linear motion.
- 8mm L30cm smooth rod, for the linear rail for the linear motion.
- Pillow block bearing, for the lead screw.
- SCS8UU linear bearing, for the smooth rod.
- SK8 rod support (x2), for the smooth rod.
- D19L25 5x8mm flexible shaft coupling (x2), one to attach lead screw to stepper motor and one to attach pencil to DC motor.
Optional:
- Potentiometer, this will be used to fine-tune the speed of the stepper motor, so it does not move too fast towards the sharpener.”