How to Build a Remote Kill Switch

Contributors: Nate

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.