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Topic: driving 8x8 LED using 2 74HC595 (Read 12 times) previous topic - next topic

retrolefty

#5
Jul 13, 2010, 01:10 am Last Edit: Jul 13, 2010, 01:10 am by retrolefty Reason: 1
Quote
OMD No resistors! I'll burn in HELL!


Probably not, but your Arduino's processor chip indeed might.  ;)

Lefty

fatalkeyv

#6
Jul 13, 2010, 05:37 am Last Edit: Jul 13, 2010, 05:39 am by fatalkeyv Reason: 1


(DS is connecting to Pin 12 sorry)

ive posted my schematics as you requested. i dont have any software so i made it using MSpaint =P

is there anything wrong with my circuit?

mrmeval

#7
Jul 13, 2010, 07:54 am Last Edit: Jul 13, 2010, 07:54 am by mrmeval Reason: 1
I won't comment further in the matrix, have only worked with shift registers.

You can save some digital pins chaining the serial on the 595's together. You would unlatch them so there is no output, serial out the data to them then latch them. Using that you can daisy chain them to run more 8x8 displays and you'd not run out of digital pins on the Arduino. Once you've written a function the code is easy to read and maintain.

So far I've strung together 32 of 595 chips. I switched to HEF4794 due to it's higher current.

If it was designed by man it can be repaired by man.

Grumpy_Mike

Quote
is there anything wrong with my circuit?

Not so far but it will depend on your software. When you write the multiplexing make sure that 2803 is the one that you put only one zero on at a time and put the data for that row on the top 595. This is the inverse of normal multiplexing. It is needed because the 2803 can sink enough current for 8 LEDs but the 595 can only source enough current for one LED.

s3n4te

#9
Aug 01, 2010, 08:05 pm Last Edit: Aug 01, 2010, 08:51 pm by s3n4te Reason: 1
Quote
... make sure that 2803 is the one that you put only one zero on at a time and put the data for that row on the top 595.


What do mean by that? Do mean that 1 led can only be turned on at a time?

Or do you mean that each pin on the 595 can only handle 20mA on each pin, and that I can only turn on 1 darlington pair at a time?

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