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I have these 230V AC indicator LEDs, which I'm using in a project to indicate when I have various switched circuits live.

Due to space constraints, the switched lives of these LEDs are routed through a ribbon cable (DuPont 40-wire, 28AWG). This has the nasty effect of multiple LEDs lighting (dimly or brightly) when only one is directly powered.

I presume this is due to induced currents in the adjacent wires; LEDs require very little power to light.

I also have 12/24V DC versions of the indicators, but am very space-constrained. If I can light the LEDs with DC, I wouldn't suffer induction issues. However, all the circuits I've seen to detect the 240V live are too big - I have nine indicator LEDs.

Is there a simple and compact way to prevent the LEDs from glowing unless they are directly powered??

Notes

  • I have tried placing a 1/4W 100kΩ resistor across the L/N for the LED, and a 22kΩ resistor, but neither had any perceivable dimming effect when the LED was off.

  • Placing a resistor (from 22kΩ - 1MΩ) in series with the live had no effect.

  • When 'unpowered', the voltage drops from 240V 50Hz to ~72V 50Hz.

  • Routing the live through a standalone wire prevents the capacitive coupling (thanks @brhans for correction).

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  • \$\begingroup\$ Hi and welcome to EE. You can edit your additional info into the question for consistency. Also if you could add pictures of the mounted LEDs and the ribbon cable as well, it'll be helpful. \$\endgroup\$
    – MiNiMe
    Commented Oct 19, 2023 at 20:34
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    \$\begingroup\$ I'm not immediately aware of any common ribbon cable that's rated for use with 230Vac. Do you have a link to a datasheet for the cable you're using? If it's just plain old 0.05" pitch ribbon-cable, and you have a single neutral and multiple lives, then you likely have significant capacitive coupling (not induction) between adjacent lives in the cable. You could probably reduce that significantly by running individual neutrals alongside each switched live, but you'd still be playing with fire (possibly quite literally) if the cable isn't rated for that voltage. \$\endgroup\$
    – brhans
    Commented Oct 19, 2023 at 20:44
  • \$\begingroup\$ @brhans Thanks; as each LED pulls a maximum of 20mA I would think there was no issue in using a ribbon cable? The ribbon is 28AWG DuPont wire, so it should be capable of carrying up to 1A. I crimped the ribbon myself, so I could use higher gauge wire, or replace the ribbon with individual wires. \$\endgroup\$
    – thargy
    Commented Oct 19, 2023 at 21:29
  • \$\begingroup\$ @MiNiMe it's just a standard DuPont 40-wire 28AWG cable, it's about 100mm long, and in pretty rainbow colours. I'm not sure a photo would add anything. The LEDs are panel mount (as shown in the amazon link). If updated the initial question with my notes as requested. \$\endgroup\$
    – thargy
    Commented Oct 19, 2023 at 21:34
  • \$\begingroup\$ It's not its current rating I'm concerned about, it's the voltage rating of its insulation. \$\endgroup\$
    – brhans
    Commented Oct 19, 2023 at 21:36

1 Answer 1

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Thanks for the help. Ultimately, I removed the ribbon cable and replaced it with lots of 20AWG wire with spade connectors.

I then left the wires in a nice, uncoordinated mess to reduce the chance of capacitive coupling, and the LEDs no longer glow.

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