Arduino & 74hc595 question

Other Hardware General Electronics
2
  1. How much current does a 74hc595 need? 20mA or 70mA?

the 595 itself needs very little to function, most can handle around 35ma per output pin max, but a max of 70ma for the entire package

  1. If 70mA, can 5V arduino pin supply 350mA? What is the maximum current draw from arduino?

Input / Output pins that run though the chip can handle a max of 40ma, 200ma for the entire package (maybe 250 I dont remember). The voltage supply could supply 350ma, but you would be getting close to the edge.

  1. Can arduino sink all the current from LEDs? 32*8.5mA =~ 275mA?

if your running it though the i/o no, same as above, if your running it direct to ground yes