PAGE 089 OF 150 · TIMERS, FLASHERS & DIMMING
Knight-Rider Style Scanner
A scanning light sweeps back and forth.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
The effect
A scanner lights LEDs one after another from left to right, then back again, creating a moving dot.
How to do it
- Use a row of six to ten LEDs on a microcontroller or shift register.
- Step forward through the LEDs, then step back without repeating the end ones.
- A step time of 50 to 100 milliseconds looks natural.
Smoother look
Leave the previous LED partly lit using PWM to make a fading tail. Red LEDs complete the familiar look.
REMEMBER
Switching an LED on and off quickly can look like steady dimmer light.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.
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