Since I keep forgetting what pins I used for the ‘595 ICs which drive my 16 segment LED clock, here the pinout:
1: Vcc 2: GND 3: /SCK 4: NC 5: SER 6: NC 7: /RCK 8: NC 9: 10: NC
Since it’s HC595, Vcc is 2 up to 6V
And while on this topic, the 16 segment has this order when sending a 16 bit stream:
t-s-r-n-m-k-p-u-h-g-e-f-d-c-b-a.
Bit 0 is t, bit 15 is a.