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The matrix does not work

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New Member
The attached circuit diagram and hex file I received from my friend. It works well with the Proteus. But when practically created, it does not work. Anyone can guess what is the reason for it. I have only the circuit and the hex file.



Well-Known Member
Most Helpful Member
I can't comment on the hex file but the schematic may have some problems.

There are no resistors to limit the current to the LEDs.
Three LEDs are fed per NPN transistor so the one with the lowest Vf will light and the other two may not.
Each port pin has to sink the LED current - can the ports handle a total of 24*LED current?


Tony Stewart

Well-Known Member
Most Helpful Member
If Common Anode then switch must have Rce or RdsOn to drop < 0.1V with all on.
Then other side must be current regulated..
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