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Driving LED DOT Matrix with ULN2803 and 74LS138

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jean12

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Hello there ,can you please help me to drive those dot matrix by proving a drive ULN2803 bebween the 74LS138 and DOT MATRIX.
I tried to do that but I failed.Please help.

without the drive the circuit operates very well in simulation but on the board with physical implementation;it doesn't work,I just see some column shifting.

See my project here attached.
 

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  • FOLDER.zip
    85.9 KB · Views: 119

If you put ULN between 54LS183 and matrix then you have to interface cathodes with ULN because ULN can only sink current. Rotate the matrix 180 degree and then flip along x - axis. Now you can connect cathodes to ULN. The data will be inverted. So, invert your matrix array elements.

Edit: I was wrong. He is shifting 0x01 at the o/p of LS138. So, you don't have to change anything with the matrix. Just put a NOT gate abd ULN between LS138 and matrix.
 
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the not get will solve the issue??
 

with post #2 above he said that the ULN is inverting the input so the LED are not working as they might so he said I have to connect a NOT gate before I put the ULN for reinverting those output.

Thanks.
 

I added the NOT gate but I got nothing right at the output(on the DOT Matrix).
can you help me to replace the 74HCT595 from (https://embedded-lab.com/blog/?p=2661) with 74LS164 so that I can scroll the text using ULN2803.

Thanks.
 

Qo of which circuit?
 

Dear jayanth.devarayanadurga, here is the complete folder for the proteus schematic and ccs c file.


Thanks.
 

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  • DOTMATRIXSCH.zip
    120.9 KB · Views: 100
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