For circuits using TTL ICs the supply voltage is a great concern and a slight increase in supply from the rated 5V may damage the IC. Using fuses alone does not solve the problem because a fuse may take several milliseconds to blow off and that’s enough time for the IC to get damaged.
Circuit diagram with Parts list.
- Assemble the circuit on a general purpose PCB.
- If 1A Bridge is not available, make one using four 1N4007 diodes.
- The trip voltage can be varied by varying the values of D2 and R2.
- All capacitors must be rated at least 25V.
- The transformer T1 can be a 230 V AC primary, 12v secondary, 2A step-down transformer.