Blasting machine

A blasting machine or shot exploder is a portable source of electric current to reliably fire a blasting cap to trigger a main explosive charge. It is mostly used in mining and demolition.

Two blasting machines. At rear is one where the trigger works by depressing or raising the handle; at fore, one where the handle is twisted

The use of the term "machine" dates from early designs that used an electrical generator operated by winding a rotary handle or pushing down a T-handle. Modern blasting machines are battery-powered and operated by key switches and push-buttons, and do not resemble the older designs.

A typical "capacitive discharge" blasting machine works by charging a capacitor from a battery, then discharging the capacitor through an external circuit, called the firing line, to fire the blasting cap.[1] While the machine is idle, an "internal shunt" is connected across the output terminals so that any stray voltages induced in the external circuit, for example by nearby radio transmitters, are harmlessly short-circuited without triggering the blasting cap. The machines also typically include an "abort" feature to discharge the internal capacitor without firing the cap.

The first satisfactory magnetic induction blasting machine was constructed in 1878 by Henry Julius Smith of Mountain View, New Jersey.[2] Its mechanism consisted of a T-handle that was pushed down; the lower end of the handle was a rack that drove a pinion, which in turn drove a high-voltage magneto, which generated the high voltage that is required to detonate the blasting cap.