Warm Glow LED

Using Arduino LEDs and Multiplexing
#1

Hello,

I am new this and I actually have a question about how i can design warm glow LED.

What's warm glow LED. It is two sets of LEDs.

The set of LEDs which are at a color temperature of 2700K are totally lit at full power delivering warm, familiar, comfortable light. But as the lamp is dimmed, the 2700K LEDs get less power while the second set of LEDs, which are at very warm 1800K are given power. As the lamp is dimmed further, the light from the two sets of LEDs continues to mix--less and less power goes to the 2700K LEDs and more and more goes to the warmer 1800K LEDs. The light output actually gets warmer and warmer with the lamp finally delivering a very warm 2200K.

Anyone have any idea how I can design a circuit to control the current that pass through the LEDs ?

Thanks in advance,

#2

Hi,

You would control the current with Pulse Width Modulation (PWM). With PWM, the current that flows through the led is fixed, but it is switched on and off very rapidly, too rapidly for the eye to notice. The % of the time the current is on versus off determines the average current and the perceived brightness.

The Arduino Uno has 6 outputs which can do PWM. However, they can (normally) only be set to 255 levels. Suggest you start by experimenting with just two 5mm leds, warm white and cool white (each with a series resistor, e.g. 220R) to see if you are satisfied with the effect. If not, it may be possible to increase the available levels.

Once you have the effect working as you want, you can think about the current requirements of the whole lamp, and how the Arduino can handle those.

Paul