Simplest way to replace a variable resistor with a digital equivalent

Thread Starter


Joined Aug 23, 2016

Newbie here.

I currently have a LED driver with a dimming function that is controlled via a variable resistor and connected via low and wiper on the variable resistor.

I would very much like to replace this with a digitally controlled equivalent. I am looking at something like the AD5220. But I am unsure how to wire the pins.

I know:

- and + for power to AD5220
A and wiper for output to LED driver
But how to move wiper?

I want to control this so that the wiper can be moved "up or down" in either direction via a signal pulse, which is the bit I am struggling with.

Any help much appreciated.



Joined Nov 18, 2016
Chip enable = Low on pin 7.
Up = High on pin 2. Down = Low on pin 2. Pull pin 1 low to clock the IC.
"Two pins with the remarkably unimaginative names “A” and “B” provide access to the ends of the ladder, while a third pin, known as the Wiper, can be connected internally with any of the taps. Although the resistance between the Wiper and A or B changes in small, discrete steps, the transition is smooth enough for many purposes, such as adjusting the volume on a stereo."


Joined Sep 22, 2012
I'll suggest changing to PWM drive, all the power, none of the heat.
If your range is simple (>10% <90%) a 555 pair works well (1 cadence, other duty cycle).
For real 0 - 100%, I use a micro with it's timer module.
Either way, pending load use a real FET driver.
Light loads can use transistors, but on big loads. the junction voltage drop will be a problem.
I've designed Many of these, from treadmill motor speed to LED illumination control.