8*8 dot matrix display

[hulkGuy]

My circuit diagram can't work at all,who could please tell me what's going wrong with my design...SOS!!!

 

[hulkGuy]

64 dot matrix display

just now forgot to press add attachment...My circuit diagram can't work at all,who could please tell me what's going wrong with my design...SOS!!!

=>resistors that used in the circuit are 100ohm and 1k ohm
=>transistors code....2N3906
=>multiplexer code...74LS138
=>capacistor...0.1uF

 

[john1]

well the matrix looks right,
the PNPs look right,
the 138 is a 3 to 8 way decoder
i havent checked the connections,
or the logic to the bases,
which wants to be high i think to shut the transistors,
which seem to be wired as emitter followers,

i have a feeling that the 138 gives a logic signal high,
but i will have to check ...

the straight output from the port
is only capable of a signal output,
but i would think it could operate an LED alright.

If the circuit here is ok,
then i would suspect the program feeding the port ...

 

[john1]

just had a bit of a look at 74-138 info,
yes the outputs are 'normally high'
and are taken low according to the binary input.

Only one of the outputs goes low at a time,
and should make its associated transistor conduct.

That seems fair enough for the column of 8 transistors.

As for your rows of 8 port outputs,
the appropriate row would have to go 'High'
to light an LED.

That you would have to check for yourself.

See what others say, there may be other things
to check as well.

Regards, John