A circuit that can be used to flash two Christmas stars alternatively is given here. The IC1 NE 555 is wired as an astable multivibrator here. When there is a positive pulse from the output of IC1, the transistor Q1 conducts and the relay K1 gets activated. The lamp L2 connected via the N/O contact of the relay glows. When the output pulse of the IC goes low, the Q1 goes OFF and the relay gets deactivated. Now the lamp L2 extinguishes and the lamp L1 connected via the N/C contact of the relay glows. This cycle continues as long as there is power supply for the circuit. The timing of the lamps can be adjusted by varying the preset R2.

Circuit diagram with Parts list.



  • Assemble the circuit on  a good quality PCB.
  • Power the circit from a 9V DC power supply.
  • The preset R2 can be used to vary the timing of lights.
  • The IC1 must be mounted on a holder.


  1. Any one have PLL 15 watt FM exciter???