help: LED's with Auto dimming display

Thread Starter


Joined Aug 14, 2012
i'm building a digitally based, analog display clock using LED's for the display. also, a microcontroller is used ( ATmaga168). i need the LED's to be Auto dimming (reduces the intensity
of the LED display when the environment is darkened and restores
brightness in normal light). actually im kinda lost at designing such circuit. should i use a photo resister? is it possible to use shift registor?? any idea will be useful. thanks in advance..


Joined Sep 9, 2010
How are you controlling the current supplied to your LED display? Dimming is easy if you are using PWM control - you can just decrease the duty cycle and thus the average current and brightness.

Detecting the light level is easy with any LDR (light dependent resistor). I usually see a CdS cell used for this, so I suppose that's the cheapest way to do it.