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further reducing matrix backpack brightness
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further reducing matrix backpack brightness

by rob_ on Wed Dec 05, 2018 5:30 pm

I have a couple of 'Adafruit 16x8 LED Matrix Driver Backpack - HT16K33 Breakout' connected to four 'Miniature 8x8 Yellow LED Matrix' supplied from 5V.

I find even with setBrightness(0), they are brighter than I wish (although it definitely has an effect).

Is there any way to reduce the brightness of the LEDs further in a controlled way such that all are equally bright?

Presumably the PWM won't go any lower, is there a way to control the current supplied?

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Re: further reducing matrix backpack brightness

by adafruit_support_carter on Wed Dec 05, 2018 8:22 pm

That's the lowest the PWM can controllably go. The lowest setting is 1/16 (see below). If you are driving the display with 5V, you can switch to 3.3V and that will make it a little dimmer.

ht16k33_dimming.jpg
ht16k33_dimming.jpg (71.61 KiB) Viewed 96 times

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Re: further reducing matrix backpack brightness

by rob_ on Thu Dec 06, 2018 6:24 pm

Thanks, but I don't have easy access to 3.3V (Nano) and the driver may be less well behaved outside its defined operating conditions. Adding a neutral density filter in front of the matrix might be a better option than a 3.3V regulator.

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Re: further reducing matrix backpack brightness

by SteveMann on Sat Feb 16, 2019 8:42 pm

adafruit_support_carter wrote:That's the lowest the PWM can controllably go. The lowest setting is 1/16 (see below). If you are driving the display with 5V, you can switch to 3.3V and that will make it a little dimmer.

ht16k33_dimming.jpg


How do I control the brightness?
I stumbled on the answer - by experimenting.
Code: Select all | TOGGLE FULL SIZE
 alpha4.begin(0x70);                             // pass in the I2C address of the alpha-numeric display
 alpha4.setBrightness(1)

Is this documented anywhere? What is the range for Brightness(x) ?

Steve

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Re: further reducing matrix backpack brightness

by adafruit_support_carter on Mon Feb 18, 2019 3:27 pm

There is a currently on going effort to do some house keeping on all the Arduino libraries. Part of this will be to add automated documentation as described here:
https://learn.adafruit.com/the-well-aut ... ry/doxygen
Once that is done, each library / repo will have an online reference.

This is a huge effort with no guarantee of when a specific library / repo will be taken care of. So just keep checking back.

Until then, it's either covered in a Learn guide, or shown in an example, or if all else fails, check the source code.
https://github.com/adafruit/Adafruit_LE ... pack.h#L60

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Re: further reducing matrix backpack brightness

by SteveMann on Tue Feb 19, 2019 1:41 am

adafruit_support_carter wrote: or if all else fails, check the source code.


Which would be GREAT if your programmers would learn what a comment is.

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