595s and 8x8 LED matrix

george miyagi

hi
spent the whole day trying to get an 8x8 LED matrix working on the 595.
all the schematics posted around are for 7x5. Can anyone help/give advice?
tx

Newzed

Do you have ExpressPCB?· I have a schematic showing how rows are connected to a 595/2803 and columns to a 595.· I'll need your e-mail address.

george miyagi

Thanks Newzed.
sent mail to your AOL account. don't have ExpressPCB though, on a Mac :-(
g

Newzed

George, just wanted to see if I could post a bitmap of the schematic.· Jon's schematics always look good, but most of mine are pretty sad.· We'll see.



Sid

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Sid Weaver
Need a bezel for your LCD?

Newzed@aol.com

Newzed

Hey, that turned out pretty good - a little bit large but certainly clear.



Sid

Jon Williams

You left the current-limiting resistors out of your circuit.

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Jon Williams
Applications Engineer, Parallax

allanlane5

Yeah, where's the current limiting resistors? If he builds it as you've set it, he'll burn out his LED's the first time he turns it on.

Newzed

Jon, all of my LEDs are resistorized and sometimes I forget the resistor.· Also, the CE drop across a 2803 is about 1 volt at low current levels and pulsing the LEDs at a fairly rapid rate reduces the average current somewhat.· Still, curent limiting resistors are a good idea if your LEDs are not resistorized.

Thanks for bringing that up.

Sid

Newzed

Allan, I told him in a separate e-mail about the resistors.

Sid

Newzed

Here is Rev A of the LED Matrix schematic - I forgot the resistors.

Sid