How to controll more than one LED with one potentiometer?

Thread Starter

arisfren

Joined Nov 19, 2020
2
Hello. I'm working on a 4 digit digital wall clock and I want to add a potemtiometer to controll the brightness of displays. I'm using a common cathode 7-segment LED displays and each cathode is connected directly to outputs of a demultiplexer which controlls what display is currently on (I'm making basically the same display that Ben Eater made in this video)
I'm planning to add a potentiometer to dim all displays at once, but I have no idea on how to do it without using Arduino. Is it even possible?
Thanks in advance for helping.
 

Sensacell

Joined Jun 19, 2012
2,820
You will need to implement a duty-cycle (PWM) modulation scheme to control the brightness, a linear solution is going to be awkward.

Perhaps you can make a PWM generator and control the EEPROM OUTPUT ENABLE line to PWM the LED's
 

Thread Starter

arisfren

Joined Nov 19, 2020
2
You will need to implement a duty-cycle (PWM) modulation scheme to control the brightness, a linear solution is going to be awkward.

Perhaps you can make a PWM generator and control the EEPROM OUTPUT ENABLE line to PWM the LED's
Just tested it with an Arduino and it worked!
Thanks a lot for help
 
If you were to use individual digital pots, individually addressable by an MCU, it should work fine. A single pot can then be used as an input to one of the ADCs on the MCU. If you use digital pots, make sure it's on the low side, otherwise the voltage on the pots will be too high.
 
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