How to Build a Remote Kill Switch

Contributors: Nate
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System Requirements

Here are the design requirements for my system. These should fulfill the kill switch safety requirements of the A+PRS rules.

  • If user presses the green button the system should energize the cut-off relay allowing power to flow to the motor.
  • If user presses the red button the system should de-energize the cut-off relay shorting the + and - of the motor causing the motor to brake.
  • If user presses the yellow button the system should assert a signal pin. This will be connected to the master controller to let it know that the race is in “yellow flag” mode.
  • If the vehicle fails to hear from the remote after a certain length of time the vehicle should go into safety-shutdown (de-energize the cut-off relay causing engine to brake).
  • If the remote fails to hear a response from the vehicle (out of range), then go into disconnect mode (blink all three LEDs).
  • If the link is re-established, then start in safety-shutdown mode.

I broke the killswitch system into two parts: the Vehicle Control Unit that lives on the vehicle and the Remote Control Unit that the human holds in their hand.

Remote control electronics

The electronics in the hand held remote (RCU)

Vehicle Control Electronics

The electronics on the vehicle (VCU)