ADWSystems
Member
So here's the scenario:
I have a circuit that requires +12VDC and +9VDC. Although I could use +12V for everything there are two catches. First, it powers an Arduino Uno and +12V is at the upper input voltage limit, secondly the ripple on the +12V supply is reflected in the attached sensor readings. I can't use straight +9 because of the +12V components (mainly relays) elsewhere in the circuit. The plan from the start was to add a separate 7809 based power supply (just a couple of caps and the chip). The ripple from the power supply is about +/- 0.5V at 7ms (~142Hz). How do I size the caps for the 7809 to reduce the ripple as much as practically possible?
I have a circuit that requires +12VDC and +9VDC. Although I could use +12V for everything there are two catches. First, it powers an Arduino Uno and +12V is at the upper input voltage limit, secondly the ripple on the +12V supply is reflected in the attached sensor readings. I can't use straight +9 because of the +12V components (mainly relays) elsewhere in the circuit. The plan from the start was to add a separate 7809 based power supply (just a couple of caps and the chip). The ripple from the power supply is about +/- 0.5V at 7ms (~142Hz). How do I size the caps for the 7809 to reduce the ripple as much as practically possible?