I'm playing with a strip of APA102 LEDs.

When VCC is disconnected, but GND, Data, and Clock are left connected, some of the LEDs faintly blink red, which I'm guessing is due to residual power from Data/Clock coming from my microcontroller.

When I add a capacitor however, this completely goes away.

As I understand it, capacitors help regulate power by filling in gaps in voltage should they come up. But how does it work when there isn't any power flowing?

  • \$\begingroup\$ You'll need to share your schematic if you want us to understand how there can be data and clock signals present when power is off. \$\endgroup\$
    – The Photon
    Dec 14, 2019 at 6:27
  • \$\begingroup\$ The strip has 4 pins. I mean power off as literally disconnecting only the VCC pin. I'm hooking up a toggle switch to this. \$\endgroup\$
    – House3272
    Dec 14, 2019 at 6:30

1 Answer 1


No, capacitors do not regulate voltage when power is off. Your terminology is incorrect.

What capacitors do is serve as a short-term charge reservoir which provides charge when the voltage droops which helps keep it up, and absorbs charge when the voltage spikes which helps keep it down.

They are, however, finite reserves of charge and need to be replenished from a power supply.


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