Electronics

For the basic usage of the robot arm, we need 3 type of boards: REF control board 42 motor control board (for NEMA 17 motors) 20 motor control board (for NEMA 8 motors)

And we will dive into the details of each board in the following sections.

REF

• REF board render image

• REF board front side and back side spec

Hardware specs

Main processor	STM32F405RGT6
Main processor features	Arm® 32-bit Cortex®-M4 CPU with FPU, Adaptive real-time accelerator
Main Processor memory	1 Mbyte of Flash memory, 196 Kbytes of SRAM
Minor Processor	ESP32-PICO-D4
Minor processor features	single 2.4G Hz Wi-Fi and Bluetooth combo chip
Communication interfaces	3 x CAN bus, 1 x UART, 3 x GPIO, 1 x USB TYPE-C
CAN tranceiver	SN65HVD232DR
USB processor	CP2102
Display	OLED 128x80 screen
Programming interface	SWD
Buck module	ME1336 (5V), LP2992 (3V3)

• Project files (Altium)

Operating limits

Power supply	9V minimal, 12V maximal voltage
On board operating voltage	3.3V, 5V
Current	Max 2A

Motor-20 & Motor-42

Motor-20 and Motor-42 boards are basically the same but with some minor differences.

• Motor-20 board render image

• Motor-20 board front side and back side spec

• Motor-42 board render image

• Motor-42 board front side and back side spec

Hardware specs

Processor	STM32F103CBT6
Processor features	Arm® 32-bit Cortex®-M3 CPU core – 72 MHz maximum frequency
Communication interfaces	2 x CAN bus
CAN tranceiver	SN65HVD232DR
Stepper drivers	TB67H450FNG
Stepper drivers features	PWM, 50V, 3.5A max
Programming interface	SWD

Operating limits

Power supply	18V minimal, 24V maximal voltage
Current	Rated current 2.5A, maximal current 3.6A

Physical properties

Dimensions

• REF board (mm)

• Motor-20 board (mm)

• Motor-42 board (mm)

3D CAD models

• REF board
• Motor-20 board
• Motor-42 board

Connections

The connection diagram is shown in below. This is a series connection and each PCB has 4 lines (VCC, GND, CAN_H, CAN_L) connect to it.

Connectors

• REF
  • SH 1.0 2P (CAN bus)
  • SH 1.0 3P (SWD)
• Motor-42
  • SH 1.0 2P (CAN bus)
  • SH 1.0 3P (SWD)
  • PH 2.0 2P (POWER)
• Motor-20
  • SH 1.0 2P (CAN bus)
  • SH 1.0 3P (SWD)
  • Dupont 2P (POWER)

Attach driver to stepper motors

This step is crucial in the construction of the robot arm.

The encoder, a magnetic sensor, is soldered onto the center of the PCB. To ensure accurate homing and control of the stepper motor, magnets need to be attached to the motor axis. The quality of this installation directly affects the functionality of the system.

Magnets

!!! The magnets need to be radial magnetization !!!

• Motor-20: D5 x 1.5 * 5 (mm)
• Motor-42: D7 x 1.5 * 2 (mm)

Isolation

• Motor-20 isolation sheld
• Motor-42 isolation sheld

Installation

Let's take Motor-20 for example. Here is the full view of all the components. Use fast dry glue to glue magnet to the end of stepper motor axis.

Then, let's install isolation shield and motor driver on the back of the motor.

Repeat this process to all the motors and we're ready to go to wiring and test.

Wiring

Follow this diagram to wire your Motor driver board to REF control board.

After sucesssful wiring of the robot it should look something like this.

• Wiring with 3 Motor-42 boards

• Wiring with 3 Moto-42 boards and 3 Motor-20 boards

• 3 motors testing video

• Full setup testing video