LED VU Meters, Encoders and SSD1306 Displays

[TK.]

I can confirm that ULN2803 helps to get consistent brightness.

Proven in the LRE8x2x4 project:

 

For best brightness results, consider to use 8x16 matrices (each matrix outputs 8 meters, each with up to 16 LEDs), and not a 16x16 matrix, because than more meters share the same row SRs, than less time per meter to display the pattern!

 

Best Regards, Thorsten.

[ibanman555]

Great! I will look into integrating the 2803 into my circuits to assist in proper brightness. Additionally, would it help for me to provide +5 voltage to the circuits from an AC or DC power supply (toroidal) to help the current draw?

You'll need to excuse my noobiness, but what I am looking to achieve here is a meter 32 leds tall. Times 64 of those. When you say "8x16" or "16x16", you are referring to the number of LEDs high X wide, correct? Later this evening I will sketch up a diagram of what I hope to achieve using the 8 (or 3?) DOUT boards.

The reason I ask is because I can place 32 LEDs on one DOUT board. Then, Make the matrix using another DOUT board giving me 1,024 LEDs, in theory. Then add an additional DOUT board across, giving me the total 2,048 LEDs capable. So, 64 meters across, 32 LEDs tall. Is this possible, or am I configuring this the wrong way??? Thanks for your help!

[TK.]

Additionally, would it help for me to provide +5 voltage to the circuits from an AC or DC power supply (toroidal) to help the current draw?

 

The current draw isn't that high, because LEDs are time-multiplexed.

A 1A PSU should be enough, this can be delivered from a USB hub based PSU.

 

but what I am looking to achieve here is a meter 32 leds tall.

 

The firmware doesn't support LED matrices with 32 LED rows, 16 LEDs per row is the limit (and I can't change this anymore due to conceptional reasons).

 

 

The reason I ask is because I can place 32 LEDs on one DOUT board. Then, Make the matrix using another DOUT board giving me 1,024 LEDs, in theory.

 

It isn't a good idea to construct a matrix this way (and similar to the 16 LEDs per row max limit, also the column selection lines are limited to 16 for good reasons).

 

E.g. if a matrix has 8 selection lines (as proposed above), each LED row will display a pattern for 12.5% of the reload period.

With 16 selection lines (possible, but not so bright anymore), each LED row will display a pattern for only 6.25% of the reload period anymore. The pattern is still visible, but it's very dimmed.

With 32 selection lines (your idea...), each LED row will display a pattern for only 3.125% of the reload period. I guess that with such a short duty cycle nothing will be visible anymore!

 

Instead it's better to use multiple matrices (meanwhile up to 16 matrices are supported) with 8 selection lines each.

Each matrix will require 3 DOUT SRs (one for 8 selection lines, two for the 16 LED pattern)

 

Best Regards, Thorsten.

 

 

[ibanman555]

Ok. Thanks for explaining this... back to the drawing board...