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Electrical System
/tech/electrical/
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Electrical Parts:

  • Arduino Uno microcontroller
  • CNC stepper motor shield with DRV8825 stepper motor drivers
  • Nema 17 Stepper Motors (12V 0.4A)
  • Servo motor - hobby grade

![block diagram]({{ site.baseurl }}/assets/images/electrical_block_diagram.png)

The Arduino receives instructions from a computer over serial. It drives the steppers with a CNC stepper motor shield with DRV8825 stepper motor drivers.

Decisions:

We chose to use Nema 17 stepper motors because they are a good compromise between cost, size, and performance. The end-effector is not very heavy, and with counterweights the motors zoom it around the board with ease. We are pleased with the precision and speed of these motors.

We use a standard CNC stepper motor shield with DRV8825 stepper drivers. This is a standard way to drive stepper motors with Arduino. The DRV8825 is controlled with two pins, one is used to indicate direction, the other triggers a step.

You can read more about the stepper motors and shield [in this blog post]({{ site.baseurl }}/2017/11/17/Stepper-Driver-Update.html).

A hobby grade servo is good enough for our tool changer. We control it using PWM.