PAGE 030 OF 150 · COLOURS, SIZES & TYPES
Flashing LEDs
Built-in circuitry makes some LEDs blink without outside parts.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
How they work
A flashing LED contains a tiny integrated circuit next to the chip that switches current on and off, usually once or twice a second.
Using one
- Check the datasheet for supply range. Many work from about 3 to 5 V.
- Higher voltages often need a series resistor.
- Respect polarity, since the internal circuit can be damaged by reverse voltage.
Limits
The flash rate is fixed, so it cannot be changed or dimmed with PWM. For adjustable blinking, use a timer circuit or microcontroller with an ordinary LED.
REMEMBER
Colour is set by the semiconductor material, not by the plastic lens.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.