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Topic: Driving many leds with multiple 595 and current (Read 2045 times) previous topic - next topic

demym

Hi,

i have a project in which i drive many leds using the 595s and arduino... each lead has its limiter resistor (220ohm)...

but i've read that the 595 is not able (for its current limitation) to drive more than 4 leds.... is there a way to interpose a 'driver' between 8 leds and each 595 that makes me bypass the current limitation ?

Consider that the project would drive several sets of 595+8leds each, and that i have a separate board for each 595+8leds set.

I'm already using ULN2803 to also drive relays in the same project; can the ULN be used with leds too ?

thank you very much

larryd

No technical PMs.
The last thing you did is where you should start looking.

CrossRoads

Or use a shift register that can sink (connects to cathode side of LEDs) high current amounts, up to 150mA continuously from each output - TPIC6B595.
Operates just like 74HC595.
Shift in a 1 to make an output go low, just as if you had 74HC595 and ULN2803.
http://www.ti.com/lit/ds/symlink/tpic6b595.pdf
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.

sensai

I haven't yet seen CrossRoads wrong, even when I can't understand his technical "gibberish" which I have to spend hours researching numbers and cross referencing information from one source to another, merely to come up with a picture of what he was explaining LOL. You can always take it on faith with his expertise …
And that being said Max7219 drives a lot of LED's, and easy to use, even for someone like me.

demym

Thanks to all for your answers.

Crossroads idea of using a TPIC6B595 is very interesting.. but i don't think i'll be lucky enough that it would be pin-compatible with 74HC595, right ? :-)

I already have some boards done (a few ones)... i'll eventually re-design them with either TPIC6B595 ora 595+ULN (preferring the first one for reduced IC number).

Thankks very much, appreciate your help





CrossRoads

No, none of TPIC-6-6A-6B-6C-6D-595 variants are HC595 pinout compatible.
The 6C and 6D595 are 16 pins like the HC595, but different pinout.
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

#6
Mar 08, 2014, 03:18 pm Last Edit: Mar 08, 2014, 03:20 pm by CrossRoads Reason: 1
2 more, and the HC595
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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