How the led works5/9/2023 This is where we get the terminology pulse width modulation. When we change the duty cycle we are changing, or modulating the width of the pulse. As you can see from the graph the lamp is transitioning from 0% brightness to 100% brightness and then back to 0%.Īs we are repeatedly sending an on and off signal to our light, we can say that we are continuously pulsing it. If we take our flashing lamp and then plot the cycle of on and off, it will look something like this. Therefore the lamp would appear to be half as bright as it actually was when switched on continuously. If the lamp is spending 50% of the time switched on and 50% of the time switch off, the brain would interpret the brightness as half of the total brightness. Once the brain is unable to perceive the pattern of switching on and off, it starts to average out the pattern and interprets it as brightness. What this means is if you were to look at a lamp that was flashing at an increasing rate, there would come a point where the lamp was flashing so quickly it would appear to always be on. Persistence of vision is somewhat of an optical illusion, whereby light entering the eye is perceived to be still present for some time after the the light ceases to enter the eye. It uses the same principle that a television uses to produce a motion picture. This is the magic technique that we can use to dim a LED.ĭon’t let the technical jargon in the name worry you, the concept of PWM is very simple. In this article we will cover the basics of pulse width modulation, or PWM.
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