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lostearstudio

Feb 19, 2011, 01:13 am Last Edit: Feb 06, 2015, 03:40 pm by lostearstudio Reason: erasing my account
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CrossRoads

Sounds like an interesting project.
This is a larger array I drew up recently, you can cut it down to size as needed.
I put some notes in about controlling it.
My thinking was that the Y shift registers would be set to configure the cathodes for a row, then turn an x-row on/off. set Y for the next row, turn next X-row on/off.
If you wanted a whole row, set all Ys low then turn on its x.
You don't want relays tho, keep it simpler with shift registers.

Makes sense?

You also discuss fading, for that you will need a PWM signal on the shift resister output enable so that when a row is selected, you can pulse it at 500Hz (analogWrite does that on the PWM pins) to keep it from being full on, thus looking dimmer.
I suppose that would work for Ys as well.
The problem is that the 74HC595 are not good for a lot of current. I suggest you look into TPIC6B595 from TI, good for a lot more current control.  Or something lke ULN2003 added to the 74HC595 outputs. TI is good about samples, be sure to you use your school address when requesting them. These are open collector devices so you will need a pullup on each X pin also which I didn't show.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

CrossRoads

You could also give yourself a leg up on programming by getting a pre-assembled array like this one so you could spend your time getting code working and not worry so much about getting all the diodes wired up, doing a lot of diodes on breadboard is cumersome to say the least.

http://ww.mpja.com/prodinfo.asp?number=18460+OP
they have others too, but this one had a nice clear data sheet to give you an idea.

http://ww.mpja.com/prodinfo.asp?number=16794+OP - datasheet can be found on the internet,  I have some of red & green ones. Not sure why mpja is not including links, they are usually good about that.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

CrossRoads

Ok, the way the grid works is by multiplexing.  You want 1 LED, you bring 1 Y column Low and 1 X column High.
You want a diagonal line, you hit Y1X1, Y2X2, Y3X3, etc.    You cycle thru that fast, it will look like all are on.
You want a whole row, you bring all the Ys  Low and turn on an X.
You want a whole column, you bring 1 Y low and then cycle thru the X fast.



Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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