LED LIGHTING FOR CHRISTMAS
RAJ K. GORKHALI sing light effects for decoration on festive occasions is a normal practice. Designers are coming up with varieties of electroniccircuits to fill the imagination of users. Here is an easy-to-assemble circuit for christmas decoration as shown in Fig.1. It comprises four transistors, eighteen LEDs, a few resistors and two capacitors.Transistors T1 and T2 are configured as an astable multivibrator, which means one of the two transistors is always conducting. Thus the combination produces clock pulses. The values of time-constantsformed with R6-C2 and R8-C1 pairs have been selected to produce a lowfrequency clock that is visible to human eye. The collectors of transistors
IVEDI S.C. DW
T1 and T2 are connected todriver transistors T3 and T4. These are used to light up two rows of LEDs connected in parallel with alternate clock pulses. The frequency at which LED1 through LED9, and LED10 through LED18, alternatelylight up is about 2 Hz. You can easily change this frequency by changing the values of capacitors C2 and C1. Resistors R2 and R4 are used to set the current through the LEDs. Red (LED1 through LED9)and green LEDs (LED10 through LED18) are used for simulating christmas decoration effects. For the brightness variation, you can change the values of resitors R2 and R4. Take any general-purpose PCBand cut it into a star shape. Thereafter, assemble the circuit and solder the colour LEDs onto it such that it looks like a christmas star.
Fig.2: Christmas Star
Fig.1: LED lighting circuit forChristmas
Alternatively, you can design the PCB in circular shape with a festive white lacquer finish on component side and conductor tracks on the other. Place the control circuit at the centre ofthe PCB board, with LEDs mounted along the outer edge as shown in Fig. 2. Along this edge, there are three circular tracks: The middle one is the positive supply, which goes to the anodes of all...