V0.2 Hardware
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Goals
- Making the machine wireless/battery powered
- Add a safety circuit and battery monitoring
- Improving expandability
- Making the machine compact
Electronics design
- A 12 V 6000 mAh Li-ion battery directly powers the A4988 motor drivers
- Battery voltage is monitored by the Pico’s ADC via voltage divider
- A LM2596 buck converter module converts 12 V to 5 V for the Pico
- UART, I2C, SPI, and extra GPIOs are available for easy expansion such as additional micro controller (e.g., ESP32-S3), an OLED display, sensors, limit switches, a fan, or a servo
- In this setup, the Pico works as the “spine”, and a wirelessly connected PC or additional micro controller works as the “brain”
Schematics
PCB
- Double-sided (LM2596 mounted at the bottom)
Pinout
BOM
| Category | Name | Value | Package | Fusion Library | Qty | Link |
|---|---|---|---|---|---|---|
| MCU | Raspberry Pi Pico | - | PICO-PKG-TH | RPI-Pico-Eagle-lib, RASPBERRY_PICOTH | 1 | Akizuki |
| Motor Driver | A4988 stepper motor driver carrier | - | - | Eagle-Library-Pololu (unofficial), 1182-A4988 | 4 | Switch-Science |
| Protection | Mini blade fuse & holder | 32V, 15A | - | Custom made | 1 | AliExpress |
| SBR diode (Schottky) | Peak Withstand Voltage: 30V, Average Forward Current: 15A | SBR15U30SP5 | Custom made | 1 | Akizuki | |
| TVS Diode | Bidirectional, VRWM: 45 V, VBR: 50–55.3 V, Peak Pulse Power: 400 W | TVS_SMBJ45CA | Custom made | 1 | Akizuki | |
| Regulator | LM2596 buck converter module | In: 3.0 ~ 40V, out: 1.5〜35V | - | Custom made | 1 | AliExpress |
| Capacitors | Electrolytic capacitor (bulk) | 35V, 220µF | CAPAE830X1050N | C-POL-US_ECAP-8.5MM | 6 | AliExpress |
| Ceramic Capacitor | 0.1µF | CAPC3216X135 | C-US_CHIP-1206(3216-METRIC) | 3 | ↑ | |
| Resistors | Voltage divider | 33kΩ | R1206 | R-US_R1206 | 1 | AliExpress |
| Pull-down / divider | 10kΩ | R1206 | R-US_R1206 | 4 | ↑ | |
| Pin Headers | Raspberry Pi Pico connection | - | 1×20SMD, 2.54mm pitch, square | pinhead-2, PINHD-1X20_2.54-SMD | 2 | ↑ |
| Stepper connections | - | 1×08SMD | ↑ | 8 | ↑ | |
| Motor driver logic pins | - | 1×04SMD | ↑ | 4 | ↑ | |
| I²C / UART / SPI / GPIO expansion | - | 2×20SMD | ↑ | 1 | ↑ | |
| Terminal block | Power switch / Battery connector | - | 1×2, 3.5mm pitch, straight, 300V, 10A | Adafruit, 1X2-3.5MM | 2 | AliExpress |
| Li-ion Battery Pack | 12V ~6000mAh Li-ion battery with BMS | 12V, 6000mAh | 3S2P | - | 1 | Amazon |
| Stepper motor | Nema17 (W/H 42 mm) | Standard (L 37 mm) | - | - | 4 | AliExpress |
| Servo motor | SF180M | 180° | - | - | 4 | Akiduki |
Mechanical design
- Modeling strategy (F3D)
- Use external/internal components
- Ref: Fusion 360 Components and Assemblies Explained
- Component layout
- The 6000 mAh battery at the center bottom between the motors
- The minimum dimensions defined by the four motors and the battery
- Topology optimization (Grasshopper tOpos)
- Boundary: box excluding space for components
- Loads: battery, PCB etc.
- Support: Mounting points for the motors
- Ref: Topology Optimization 101