Replacing an analog potentiometer with a digital potentiometer

Thread Starter

MattPurland

Joined May 1, 2020
1
Hi All,

My limited knowledge is making it hard for me to find a suitable replacement for a pot used to control the backlight of an LCD. The LCD in question is the following:

https://github.com/DFRobot/Wiki/raw/master/DFR0550_Schematics.pdf

I believe R6 is what I'll be replacing (it's one of those dial types). I'm unsure if the voltage (19.2v) needs to be considered as, from what I can tell, most digipots only work with ±5v. Also it's 500r, but most digipots are 10k. The current pot reduces the brightness to about half, ideally I'd like to reduce the brightness completely.

I'd ideally like a non-volatile digipot so I can 'save' the value on shutdown. I've not found anything that matches my requirements based on my limited understanding.

In terms of the interface, 3-wire serial (SPI) would be ideal.

Can anyone recommend a suitable replacement?

Thanks in advance!
 

jpanhalt

Joined Jan 18, 2008
9,435
Welcome to AAC.

What's the voltage drop across the backlight? The maximum voltage to which the pot will be exposed needs to be considered, and low voltage is a problem with many digital pots. A cheaper and often easier way is simply to use the MCU to PWM control a BJT or mosfet switch.
 
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