Driving LED DOT Matrix with ULN2803 and 74LS138

[jean12]

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.

 

[jayanth.devarayanadurga]

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.

 

[jean12]

the not get will solve the issue??

 

[jayanth.devarayanadurga]

Sorry, he is moving 0 at the o/p of LS138. When it is working why you need ULN and NOT gate? What is the problem with the design?

 

[jean12]

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.

 

[jean12]

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.

 

[jayanth.devarayanadurga]

Q0 of one stage is connected to A and B pins of next stage for cascading.

 

[jean12]

Qo of which circuit?

 

[jayanth.devarayanadurga]

Q0 of LC138 is connected to A and B (serial data pins) of next stage.

 

[jean12]

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


Thanks.