PAGE 147 OF 150 · PROJECTS
Build an LED Christmas Star Chaser
Chaser patterns suit festive decorations.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
The design
Cut a star shape from card or plastic and place ten LEDs around the outline. A 555 clock and a 4017 counter light them one after another to make a chase.
Power
Use 9 V or 12 V for the 4017, since a CMOS 4017 at 5 V supplies only a few milliamps from each output. Alternatively, buffer each output with a small transistor.
- One 330 to 470 ohm resistor per LED.
- Change the 555 timing parts to adjust speed.
- Use diffusing paper to soften the LED dots.
Hang the finished star away from heat and from anything flammable.
REMEMBER
Check the counter chip can drive the LEDs at your supply voltage.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
Explore LED clocks, stopwatches and electronics at cosycom.com.