Miniature self contained firing system

Abstract

Each of first and second switches, preferably ganged, have first and second operative relationships. In the first operative relationship, the first switch is connected across a firing device to prevent the firing device from being energized. In the first operative relationship, the second switch is connected across an energy storage device (e.g. capacitor) to prevent the capacitor from being charged. In the second operative relationship of the second switch, the capacitor is charged by an energy supply device (e.g. battery). In the second operative relationship of the first and second switches, the capacitor is connected in a circuit with the first device and a third switch (e.g. transistor). The transistor is normally nonconductive to prevent the capacitor from discharging through the firing device with the first and second switches in the second operative relationships. When the transistor becomes conductive with the first and second switches in the second operative relationship, the capacitor discharges and fires the firing device. The transistor becomes conductive when a triggering signal is introduced to a pair of terminals. The triggering signal may be filtered by a low pass filter (e.g. inductance and capacitance) to prevent noise from passing. A device (e.g. zener diode) limits the triggering signal amplitude. The filtered triggering signal charges the capacitance in the low pass filter. The capacitor charge causes a second transistor to become conductive, thereby producing a voltage across an impedance. This voltage triggers the first transistor to the conductive state to provide for the firing of the firing device.