Color Changing Led

Thread Starter


Joined Feb 22, 2008
I have an electric scooter and it's charger has an LED indicator, when the battery is not fully charged it emits red light and when it get fully charged the same LED turns green, how that is done ?, I know that it uses a different frequency for both color but how, after all an LED runs on D.C. so where does the frequency come in to picture?


Joined Jan 28, 2005
It sounds as though what is being used is a dual LED. Such an LED is actually made up of a green LED and a red LED. These dual LEDs come in two pinout styles. One style has two pins with the two LEDs connected in parallel. In this style LED, the color displayed depends on the direction the LED is being driven. Then there is the three terminal style which has the LEDs connected up in parallel. These can be driven in several ways to achieve selective illumination of the two LEDs housed in the package.

In either of the two cases mentioned above. The LED can be driven with a DC level to select the desired color. No frequency is necessary.

That said, these dual LEDs can be driven with a PWM signal to achieve a blending of the red and green to access a broader range of colors.