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Topic: Led project (Read 2 times) previous topic - next topic

dhenry

Quote
with Shift registers you'll need to provide resistor for every common anode/cathode and transistor banks to supply power


Not necessarily.

Say a 8x8 matrix, you can put the column leds on the mcu's output pins (8), and for the rows, you drive them via hc595 (or hc164). For each display cycle (one column), you present data on the column pins, and then strobe the row just once (one CLK transition), to move to the next column. So you need 8 pins + 3 shift register pins. This approach is very useful for rectangular displays.

If you are short on pins further, you can put the columns on another shift register and you are down to just 3 pins.

I suspect the arduino commity consumes a large percentage of those maxim chips.

Boffin1

Hi Crossroads,

Have you tried the Maxim chips from Tayda ?  that price is very good, I see Mouser are quoting $13  and our cheapest price here is about $10.

If I can get them cheap enough I might try playing with multiplexing.

I always used DC latched drivers on my scoreboards to try and keep the RF reception as clean as possible - everything else is perfect -  line of sight across a field with nothing near the receiver,  antenna high, and I hide the screened SM power supply away from the receiver.

But now with my new superblinding LEDs,  (   theres a photo of a display facing straight into the sun at www.scorebauds.co.za )  I have to dim the display for overcast or evening matches or the players would be blinded !

So I am dimming the TPIC chips using the notG pins connected to a pwm output of the micro,  so I might as well try multiplexing anyway  for the alpha team names....

And whats that strip board you are using in the photo you posted?  I havnt seen that here .
With my mobile phone I can call people and talk to them -  how smart can you get ?

CrossRoads

Yes Boffin, the picture I posted in reply #5 is using 4 of 8 MAX7219's I just purchased  from Taydaelectronics for $1.25 each.
The board is a big one from dipmicro.com, 18cmx 30cm
http://www.dipmicro.com/store/PCB-UNI30H

I see they are available in that size at e-bay, search for "prototyping pcb 18cm 30cm"
~$5 each, less in higher quantities.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

dhenry

Quote
Mouser are quoting $13  and our cheapest price here is about $10.


Those prices are trying to tell you something.

Boffin1

I am  not sure what the prices are telling me, thats why I asked if Crossroads had actually bought any of the cheap ones.......

I usually find Mouser prices pretty good, but then again I have never seen Tadya before.  Its still a hell of a difference in price.

And Crossroads, I have used some much smaller prototyping boards like that once.  Your pic is very tidy on top , I can imagine the flip side  :-)
With my mobile phone I can call people and talk to them -  how smart can you get ?

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