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This is Best Electronic Crowbar Circuit Diagram for AC or DC lines. For positive protection of electrical or electronic equipment, use this against excessive supply voltage. Due to improper switching, wiring, short circuits, or failure of regulators, an electronic crowbar circuit can quickly place a short circuit across the power lines, thereby dropping the voltage across the protected device to near zero and blowing a fuse. 

The triac and SBS are both bilateral devices, the circuit is equally useful on ac or dc supply lines. With the values shown for Rl, R2, and R3, the crowbar operating point can be adjusted over the range of 60 to 120 volts dc or 42 to 84 volts ac. The resistor values can be changed to cover a different range of supply voltages. The voltage rating of the triac must be greater than the highest operating point as set by R2, II is a low power incandescent lamp with a voltage rating equal to the supply voltage. 

It may be used to check the set point and operation of the unit by opening the test switch and adjusting the input or set point to fire the SBS. An alarm unit such as the Mallory Sonalert may be connected across the fuse to provide an audible indication of crowbar action. (This circuit may not act on short, infrequent power line transients).

Tthis is a very simple LED flasher circuit diagram that is powered from AC 230V mains. This Flasher can be used as a power indicator for the AC 230V mains supply. This circuit is made with few numbers of parts namely, a LED, two Resistors, one Capacitor, one Diode and one DIAC.  The DIAC act the main role to flashing the LED. DIAC is a bidirectional device. It conducts current only after its breakover voltage has been reached its threshold. Most DIACs breakover voltage is around 30 V.

When mains is connect to the circuit, the Capacitor(C1) starts charging through Diode(D1)&Registor(R1). When the voltage on the capacitor reached the DIAC’s threshold voltage, the DIAC get turn on. And LED gets Lights(flash). At the same time Capacitor(C1) goes discharges and breakover voltage of DIAC also decrease and LED turns OFF. The on off time of the LED depends on the value of Capacitor(C1)  and Resistor(R1).

Note that the flashing time of the LED shown in the animating figure is not the exact timing of ON/OFF.




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