1st of all I am a Noob here to shift registers. I was looking at the web site http://www.instructables.com/id/Led-Cube-8x8x8/?ALLSTEPS and was wondering what the chip 74HC138 is used for. Couldn't you just series the shift registers in series together to drive transistors to achieve the same results. I am wanting to build a led display that will use a 6x20 led matrix. I was wanting the capability of driving all leds at once. Thanks in advance for the help.
'138 selects the layer that will be turned on during the multiplexing.
Yes, can add another shift register to control transistors. That's how I would do it.
6x20 - would typically still be multiplexed.
Drive 6 anodes using cd74ac164,
Sink current from each column using three TPIC6B595s.
What you are saying you would not use the 74hc138 in this application.
I would not use '138, no.
Thanks for the guidance now comes the schematics and prototyping fun!
I am going to use the 74hc595 to drive the leds on the anode side can I use the 74hc595 to drive transistors to sink the cathodes.
Poor choice.
74Hc595 is only rated for 70mA total - so you only get 8-9mA per output.
cd74ac164 good for 24mA per output.
Why double up on hardware for the outputs?
Use TPIC6B595 instead, like a 74HC595 & transistor drive in one package.