Rongge

The Simple Electrification Unit circuit is intended for carrying out harmless experiments with high-voltage pulses and functions in a similar way as an electrified fence generator. The p.r.f. (pulse repetition frequency) is determined by the time constant of network R1-C3 in the feedback loop of op amp IC1a: with values as specified, it is about 0.5 Hz. The stage following the op amp, IC1b, converts the rectangular signal into narrow pulses. Differentiating network R2-C4, in conjunction with the switching threshold of the Schmitt trigger inputs of IC1b, determines the pulse period, which here is about 1.5 ms. The output of IC1b is linked directly to the gate of thyristor THR1, so that this device is triggered by the pulses. The requisite high voltage is generated with the aid of a small mains transformer, whose secondary winding is here used as the primary. This winding, in conjunction with C2, forms a resonant circuit. Capacitor C3 is charged to the supply voltage (12 V) via R3.When ...

The consumer unit (or ‘electricity meter’) cupboard in some older houses is a badly lit place. If the bell transformer is also located in this cupboard, it may be used to provide emergency lighting by two high-current LEDs. These diodes are powered via a small circuit that switches over to four NiCd batteries when the mains fails. The output voltage of the bell transformer is rectified by bridge B1 and buffered by capacitor C1. The batteries are charged continuously with a current of about 7.5 mA via diode D1 and resistor R2. Circuit diagram: LED Lighting For Consumer Unit Cupboard Circuit Diagram The base of transistor T1 is high via R3, so that the transistor is cut off. When the mains voltage fails, C1 is discharged via R1; when the potential across it has dropped to a given value, the battery voltage switches on T1 via R3 and R1, provided switch S1 is closed. When T1 is on, a current of some 20 mA flows through diodes D4 and D5. The light from these LEDs is sufficient to enabl...