DE3239628

A short circuit proof driver and alarm circuit for a solenoid actuator in a glassware forming machine is disclosed. Power to the solenoid is switched from a power source by a VMOS enhancement mode power transistor. Under normal operating conditions, the power transistor will be operated in saturation, whereby very little voltage is dropped between the drain and the source. When a short circuit condition occurs in the solenoid or connecting cable, the power transistor will be pulled out of saturation and the amount of voltage drop will become significant. Circuitry is provided for limiting current flow through the power transistor to a value somewhat above the maximum normal load current. The components of the system are selected to operate properly in the short circuit condition, thereby preventing the accidental activation of a solenoid in the glassware forming machine. A detector circuit senses the increased power dissipation across the power transistor and generates a signal to an alarm circuit to generate an alarm signal. The alarm signal can be used by an operator to determine which solenoid has failed.