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How do I dim the backlight on 20x4 character LCD with backpa
Moderators: adafruit_support_bill, adafruit

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How do I dim the backlight on 20x4 character LCD with backpa

by c15571 on Wed Jan 19, 2022 7:55 pm

I am using the 20x4 white on blue LCD character display (Product ID: 198} with the I2C/SPI character LCD backpack (Product ID: 292) On a Raspberry PI Pico (Product ID: 4864). I have everything connected and it is working perfectly.

There is one thing puzzling me though. How can I adjust the brightness of the backlight while using the backpack? The headers used to mount the backpack to the display block the ability to wire in the potentiometer that is included with the device.

Am I missing something?

Could I remove the pins from the header at position 15 and 16 on the backpack and add the necessary wiring to support the potentiometer?

Thanks in advance for the help.

TonyC

c15571
 
Posts: 14
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Re: How do I dim the backlight on 20x4 character LCD with ba

by adafruit_support_bill on Wed Jan 19, 2022 8:13 pm

The pot packaged with the display is normally used for contrast. But there is a contrast trim-pot built into the backpack.

It should be possible to do some surgery on the board to wire the spare pot in series with the backlight. But the range of adjustment is likely to be very limited as it is a 10K pot.

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Re: How do I dim the backlight on 20x4 character LCD with ba

by c15571 on Wed Jan 19, 2022 8:55 pm

adafruit_support_bill,

I missed that the pot was for contrast rather than brightness in the docs, thanks.

What value for the pot would give a better range?

TonyC

c15571
 
Posts: 14
Joined: Mon Nov 28, 2011 8:48 pm

Re: How do I dim the backlight on 20x4 character LCD with ba

by adafruit_support_bill on Wed Jan 19, 2022 9:19 pm

How low do you need to go? Something like 100 ohms would give you substantial dimming. 1K ohms should take you down to a very dim glow - if not completely off.

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Re: How do I dim the backlight on 20x4 character LCD with ba

by c15571 on Wed Jan 19, 2022 9:37 pm

adafruit_support_bill,

Not sure how much I want to dim it. The values you gave me certainly help. I will try one. If it isn't dim enough, I'll try the other.

Again, thank you for your quick response.

TonyC

c15571
 
Posts: 14
Joined: Mon Nov 28, 2011 8:48 pm

Please be positive and constructive with your questions and comments.