Introduction: 12v Universal Flasher Circuit

When we bought our second hand car, there was a flasher ckt attached to the horn of car. it was so annoying for me to have a flashing horn so i removed the flasher ckt and saved it for another purpose.

This is the universal 12vdc flasher for flashing any kind of 12vdc load(heavy or light) easily

In this project I have made ckt diagram and PCB design accordingly

Also I have attached PCB layout and ckt diagram pdf files

Step 1: Components Required

  • 12v Dc Relay
  • SC945 NPN Transistor (must see picture for pinouts)
  • Polarized Capacitors x 2 (16v, 22 uF)
  • Resistors x 4 (4.7kilo ohm)
  • Three pin terminal block (picture for reference)

Step 2: Circuit Diagram and PCB Files

At first i thought to make PCB and then upload it on instructables but due to Covid-19 situation i can't some components

the size of the PCB is about 1.5 x 1 inch

These are the actual size pcb pdf files.

You can print it out and paste on on simple pcb board

checkout the link for homemade pcb

Step 3: Working and Conclusion

Checkout the video of circuit working.

in this video i have shown a car`s indicator bulb flashing


  • it can be operate on 12v dc supplies adopters or even directly from car or motorcycle`s battery without any rectifier
  • it can flash almost any 12v load easily and also heavy loads like car horn, Halogen bulbs, etc

The only annoying thing is the clicking sound of relay so its good for outdoor purposes