Igniting detonators connected in series - using ignition machine with circuit for avoiding shunt failures and limiting charge voltage of ignition capacitor dependent upon applied resistance of series connected ignition circuit

摘要

The ignition machine has a switch formed as a thyristor, a voltage limitation section, a locking to secure an adequate charge voltage and a timer with a switch-off time of less than 4 ms. The voltage limitation section involves an additional current source (14) feeding into the current circuit (RL), an analogue-digital converter (15) separable form the load resistance (6), a timer (17), a latch (16) and a digital-analogue converter (19), the output of which is connected to an addition circuit (20) connected to the voltage limiter (7). A divider and an additional addition circuit as well as a comparator are connected to the output of the d-a converter (19). The comparator's second input is connected to a shunt and its output is connected, via a time delay element, to the thyristor (5). ADVANTAGE - Charge voltage automatically limited to lowest value according to number of detonators. Recognises short circuit as soon as signal is delivered.