The motor that comes with the MetroX kit does not draw more than 250mA but if you have a different motor, it could easily draw 1000mA, more than a USB port can handle! If you aren't sure of a motor's current draw, power the Metro from a wall adapter, not just USB.

Before beginning CIRC03, you should note the following things:

  • The flat side of the transistor should face the Metro.
  •  The striped side of the diode should be facing towards the bottom of the Metro
  • The resistor used in this circuit is different from the past two (CIRC01/CIRC02). Make sure the color bands read red > red > red


  1. Connect GND and 5V on the Metro to the red and blue power rails.
  2. Ensure the flat side of the transistor faces towards the Metro. Connect the Emitter (labled on the diagram above) to the GND rail. First connect the Base to the 2.2k Ohm resistor, then to the 5V rail. Leave the collector for now. 
  3. Connect the striped lead of the diode to the 5V rail, and the un-striped lead to the collector of the transistor
  4. The blue motor wire should be connected to the striped diode lead. Connect the red motor wire to the bottom (un-striped) side of the diode. 
  5. Re-read the notes above the diagram to ensure you did not make any errors while connecting components. It does not matter which way you connect the motor's leads for now.

This guide was first published on Aug 18, 2017. It was last updated on Jul 23, 2024.

This page (Wiring ) was last updated on Mar 08, 2024.

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