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george miyagi
06-14-2005, 02:02 AM
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
06-14-2005, 02:07 AM
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
06-14-2005, 02:20 AM
Thanks Newzed.
sent mail to your AOL account. don't have ExpressPCB though, on a Mac :-(
g

Newzed
06-14-2005, 04:02 AM
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 (mailto:Newzed@aol.com)

Newzed
06-14-2005, 04:04 AM
Hey, that turned out pretty good - a little bit large but certainly clear.



Sid

Jon Williams
06-14-2005, 07:44 AM
You left the current-limiting resistors out of your circuit.

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Jon Williams
Applications Engineer, Parallax

allanlane5
06-14-2005, 07:51 AM
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
06-14-2005, 07:52 AM
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
06-14-2005, 07:54 AM
Allan, I told him in a separate e-mail about the resistors.

Sid

Newzed
06-14-2005, 08:24 AM
Here is Rev A of the LED Matrix schematic - I forgot the resistors.

Sid