PAGE 082 OF 150 · TIMERS, FLASHERS & DIMMING
What Is PWM?
Pulse-width modulation varies the on-time fraction.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
What PWM means
Pulse width modulation switches a signal fully on and off very quickly. The share of time spent on is the duty cycle.
Numbers
- Duty cycle = on-time ÷ total period × 100 percent.
- Average voltage = duty cycle × supply voltage.
- A 5 V signal at 40 percent duty averages 2 V.
Frequency is how many on-off cycles happen per second. Because the LED is either fully on or fully off, it always receives its full designed current when lit, which keeps colour stable.
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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