Driving 4 LEDs and 4 Relays with a ULN2803?

[BlueBill]

Any thoughts on problems driving (sinking) 4 LEDs on the 5V rail and 4 Relays on the 12V rail with the same ULN2803? (diode clamp on 12V rail)

[johnwasser]

Since the 5V and 12V supplies go to the same Ground there should be no problem sinking either or both.

[MarkT]

Yup, the diodes only needed on the relay windings so that should be fine.  Don't forget current-limiting resistors for the LEDs.