| 摘要 |
Pulsating coded light energy is identified in a firing unit which converts the light energy to electrical energy which is stored in a capacitor 12 and then transferred to an ignition resistor 68 of a detonator. A light bulb 9 and an LED 15 are energised with pulsed D.C. and are respectively coupled to a solar cell 10 and a photodiode 16. Each D.C. pulse causes cell 10 to convert light energy into electrical energy at a voltage insufficient to activate resistor 68 and this electrical energy is stored in an inductor 24. Each time a transistor 30, controlled by diode 16, turns off a high voltage spike is generated and the energy inductor 24 is transferred to capacitor 12. When the voltage on capacitor 12 reaches a predetermined level, a zener diode 37 turn on FET 45 to discharge capacitor 12 through ignition resistor 68. The system only operates within a given range of frequencies and duty cycles of the pulsed light energy. If the frequency or duty cycle is too low a capacitor 31 will not charge up so that an inverter 29 then provides a low impedance across capacitor 12 to inhibit activation of ignition resistor 68. The upper frequency limit depends on the frequency response of photo diode 16 and the time constant of the inductor circuit. The light energy may alternatively be coded by wavelength instead of by pulsating frequency/duty cycle. <IMAGE> |
