A blow gun is aimed at the chest of a monkey who hangs from electromagnets. A dart is launched pneumatically with a bike pump. A thin tin foil switch is broken by the dart and causes the monkey to fall. The metal dart will impact loudly onto a metal plate on the chest of the monkey. Monkey, blow gun, dart, foil and electromagnets are stored in mechanics.
Power supply is in general use.
Set the current at approx two amps. Test fire many times.