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Why this 8X8 Matrix not working?

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Hello!

Why the ULN2803 outputs are not working? The inputs are responding

The ULN2803 has eight NPN Darlington open-collector transistors so its outputs can drive only LED cathodes.
Examine the polarity of your LED matrices and invert the 1,2,3, ... 8 pins instead of the A,B,C, ... H
(to do this in their properties window switch on the 'Edit all properties as text').
The 12 v for the ULN is unnecessary in this case ...

And ... modify also your SW to well handle the new polarity.
 

The ULN2803 has eight NPN Darlington open-collector transistors so its outputs can drive only LED cathodes.
Examine the polarity of your LED matrices and invert the 1,2,3, ... 8 pins instead of the A,B,C, ... H
(to do this in their properties window switch on the 'Edit all properties as text').
The 12 v for the ULN is unnecessary in this case ...

And ... modify also your SW to well handle the new polarity.

How to invert the pins? Can you show me hoe to do that?

Did you see that the inputs of ULN2083 is varying (blinking) but the outputs are not varying.

I checked. The top pins of led matrix from left are A,B,C,D,E,F,G,H and the bottom pins from left are 1,2,3,4,5,6,7,8.

How should be the connection. Why is that the ouptputs of ULN2083 is not varying?
 
Last edited:

How to invert the pins? Can you show me hoe to do that?
Did you see that the inputs of ULN2083 is varying (blinking) but the outputs are not varying.
I checked. The top pins of led matrix from left are A,B,C,D,E,F,G,H and the bottom pins from left are 1,2,3,4,5,6,7,8.
How should be the connection. Why is that the ouptputs of ULN2083 is not varying?

Because the matrix pins 1,2,3, ... 8 are ANODES now and the ULN cannot give positive voltage to open the leds.
Solution 1:
Y-mirror all matrices (a lot of work because full new wiring is needed)

Solution 2 (as I wrote above):
- right click on the matrix then "Edit properties"
- select 'Edit all properties as text' at bottom
- change the {INVERT=A,B,C,D,E,F,G,H} line to {INVERT=1,2,3,4,5,6,7,8}
- click OK
- make the above for ALL matrices ie modify them to Common Anode at top pins and Common Cathode at bottom pins

Then the LEDS lit now (SW was not examined ... modify if needed)
The ULN outputs are LOW or 'float' (not shown now, to see them apply 1000 Ohm pullups on every ULN outputs :))
 

I did as you said but still its not working.
 

Attachments

  • 8X8 LED MATRIX v3.rar
    21.4 KB · Views: 99

It is working but not displaying any alphabets

Your circuit (and also the software) is a row-scanning system for 8x8 led matrices (8 Common Cathode rows !!).
But the connection of the matrices is wrong, since the rows and columns are reversed.

In case of the used Proteus device (MATRIX-8x8-GREEN) the A,B,C,...H pins are the Common Cathode ROWS (horizontal lines)
and the 1,2,3, ...8 pins are the Common Anode COLUMNS (vertical lines) if the invert property remains the original A,B,C.....
So you must redraw the whole matrix from scratch:

- first delete all matrices
- then place ONE new MATRIX-8x8-GREEN device and then Y-mirror it, that the column pins (1,2,3, ..) pointing upward, toward the HC595 outputs
- now select this as a block, and - using the Block-Copy function - put all matrices to their right place
- now create a full new wiring so that the A, B, C ... pins are connected to the ULN outputs, and the 1,2,.. pins to the HC595 outputs.

Other:
- The applied row selector circuit (the 4017) is not a lucky solution, since it does not allow the "all lines switch off" , which will be needed.
- The software has not been studied, so may be also problems with the X direction (X-mirror of the matrices may need), and / or the HC595 chain must be reversed

Look at my working circuits on the forum!

Good luck!
zuisti
 

Thanks, but where are the links to the working circuits?

Hi;
You can see all my posts (click on my name then "View forum posts")
I already posted here many projects, full with source but only for Proteus. For example (PIC16 and 7x5 matrices):

- the oldest, from 2007 (a little complicated):
https://www.edaboard.com/posts/898313/#post898313

- newer and simpler:
https://www.edaboard.com/posts/1004936/#post1004936

- the newest and simplest (recommended as a start point):
https://www.edaboard.com/posts/1125963/#post1125963

- but read this too:
https://www.edaboard.com/posts/1126105/#post1126105

I cannot help more (no time) ...
zuisti
 

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