E-Kill Requirements

IARC Specification

The IARC rules discuss the specifications of a safety kill switch in depth, but in short the kill switch must abide by the following design rules.

• The safety kill switch can not be dependant on computer systems and software; it must be toggle-able using only transistor level logic and analog circuitry (i.e. no PIC or AVR).
• The safety kill switch must prevent power delivery in some way from the platform's power supply to the platform's propulsion when toggled.
• The safety kill switch must have a robust connection to a ground switch that a judge can toggle. It is expected that as soon as the ground transmitter is toggled, the aerial platform will come down immediately.

Our Design Goals.

In addition to the IARC's design specifications, Pitt RAS has its own specifications for the e-kill

• The safety kill switch must be able to allow the maximum current that the propulsion systems are capable of drawing without breaking in the event of a current spike.
• The safety kill switch must have voltage protection in the event of a voltage spike across the kill switch
• The safety kill switch must be able to permit power to the propulsion systems, without wasting power on the switch.
• The safety kill switch must be simple to explain.

High Level Design

The E-Kill circuit consists of three major parts at a high level.

• An RC vehicle radio receiver, which normally drives an RC vehicle's servos.
• A dual D Flip-Flop set up to be a type of one-shot trigger.
• A circuit breaker comprised of enhancement mode MOSFETs.

The radio receiver obtains input from the kill switch transmitter. The receiver outputs a servo driving PWM signal. The PWM signal is translated by the one-shot trigger to transistor level logic which controls whether the power MOSFETs permit power or not.

Schematics

The KiCad schematics for the V1.0 drone's safety switch can be found here