Electric timer increasing capacitor charging time - to chieve long delay, has solid state switch presenting high impedance in off state and low in on state

摘要

The electrical timer has a capacitor for generating a long time delay. The circuit contains a low leakage loss capacitor with a charge-discharge network. The branch with the capacitor has a two way solid state switch and a field effect transistor. This switch is normally open and in this mode will present a high impedance. When switched to the conducting or closed mode the impedance is low. A train of control pulses of fixed duration controls the time delay while the state of the charge on the capacitor is measured. The rectangular pulses are converted to a direct current which is used to charge the capacitor.