Go Down

Topic: 74LS164P shift register, in sinking configuration? (Read 2 times) previous topic - next topic

dhenry

Quote
did I just happen to pick a wuss of a shift register that can't do 8 LEDs,


Yes.

Quote
and need to switch to a heavier one?


Depends. You can put a npn on each output line to buffer; or you can switch to a beefier one.

CrossRoads

TPIC6x595 is good for sinking higher currents; i.e., connect to cathode end of LED, anode to +5, with current limit resistor as well sized for your LED Vf.
Check them out at avnet.com and TI.com
6595
6A595
6B595  << I use this one a lot.
6C595
6D595 << this one with 100mA/pin drive would be fine for 20mA LEDs as well.
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.

Grumpy_Mike

Quote
which consumes about 20 mA from what I hear

An LED only consumes what you let it consume, this is determined by the resistor. At 8mA it will be perfectly bright enough.

Boffin1

Quote
At 8mA it will be perfectly bright enough.


Might be OK outdoors in UK , but might not cut it in real sunshine :-)     

But the brightness of available (  economical )  LEDs seems to double every few months so it is getting less of an issue .

With my mobile phone I can call people and talk to them -  how smart can you get ?

mmelendeze

#9
Jan 09, 2013, 08:09 pm Last Edit: Jan 09, 2013, 11:29 pm by mmelendeze Reason: 1
:smiley-mr-green: Found myself an LED display (A-503GA) from an old PC chasis, only it's common anode: http://www.datasheetdir.com/A-503GA+LEDs

So in order to drive it with a shift register, the shift needs to work in sinking mode.

Can this be done with a 74LS164P? How would the hardware part go? Just invert the current direction and LEDs, so that the current flows into the IC output pins?

DS for the 74LS: http://www.alldatasheet.com/datasheet-pdf/pdf/246762/RENESAS/HD74LS164P.html

Go Up