Mutchus

Crowbar circuits are so-called because their operation is the equivalent of dropping a crowbar (large steel digging implement) across the terminals. It is only ever used as a last resort, and can only be used where the attached circuit is properly fused or incorporates other protective measures. A crowbar circuit is potentially destructive - if the circuitry only has a minor fault, it will be a major fault by the time a crowbar has done its job. It is not uncommon for the crowbar circuit to be destroyed as well - the purpose is to protect the device(s) attached to the circuit - in this case, a loudspeaker. Description There's really nothing to it. A resistor / capacitor circuit isolates the trigger circuit from normal AC signals. Should there be enough DC to activate the DIAC trigger, the cap is discharged into the gate of the TRIAC, which instantly turns on ... hard. A TRIAC has two basic states, on and off. The in-between state exists, but is so fast that it can be ignored for a...

The circuit diagram shows the over voltage protection as a feature of LM317 linear voltage regulator.Over voltages come from several source or factors which are usually in the form of transients. Transients are represented in spikes which are short and fast disturbance or change in the voltage and current component. It only occurs in circuits containing conductance and capacitance. The causes are typically from power outages, short circuits, tripped circuit breakers, lightning spikes, inductive spikes and other malfunctions from power company.  As an example using a 12V battery source, the LM317 voltage regulator can be used to obtain 6 Volts. To protect any device from over voltage, there are ways such as adding relays or a zener diode. A relay switch functions by opening or closing under the command of another circuit. But finding a relay that would limit the output from 6 V to 12 V is not easy. Fortunately, zener diodes are more abundant. A 6.2V zener diode rating can be used t...