Ive installed LED downlights in my room, these : https://www.screwfix.com/p/lap-fixed-led-downlight-contractor-pack-white-370lm-5w-220-240v-10-pack/728fj

they are controller via a smart dimmer switch, this : https://www.amazon.co.uk/gp/product/B07BKXMS6C/

they work fine, dim up and down but the lowest brightness is 10% (is still super bright), using the smart app you can set them to 1% which is much better

as the lights are all wired one to the next, to the next, i just wondered if i could permently reduce the current flow by using an inline resistor or an inline dimmer to lower the effective brightness? Basically so when the switch thinks the lights are at 10%, the power they are actually recieveing is more like under 5% brightness?

Im not an electricial so please dont shout at me if im asking for the impossible!!!


  • 1
    \$\begingroup\$ These are 220-240V lights, so they are not wired in series. \$\endgroup\$
    – user253751
    Aug 10, 2020 at 14:17
  • \$\begingroup\$ yes they are 240V, they are wired in parallel \$\endgroup\$
    – Ashley
    Aug 10, 2020 at 14:35
  • 1
    \$\begingroup\$ Right, the reason 240V (and 120V) LED bulbs don't dim well is because there is a circuit inside the bulbs which converts 240V AC into 12V DC for the actual LEDs. If you put a resistor in series with the actual LEDs, it would probably work, but you'd have to open up the bulb which is strongly not recommended (you'll break it). \$\endgroup\$
    – user253751
    Aug 10, 2020 at 14:41
  • \$\begingroup\$ LED strips don't contain this circuit (the circuit is in the controller) so they could be dimmed by putting resistors in series - but you don't need to, because dimmers for LED strips go all the way down to 0% \$\endgroup\$
    – user253751
    Aug 10, 2020 at 14:42
  • \$\begingroup\$ I know you can also get 12V LED lights but I don't know how they work. \$\endgroup\$
    – user253751
    Aug 10, 2020 at 14:48

1 Answer 1


What you want is not possible, these lights work from mains voltage (240 V AC) which the LEDs in the lamp cannot handle. So there's a power converter circuit present that transforms the 240 V AC into a (much lower) DC voltage (at a high current) that the LEDs can handle.

For dimming usually some form of PWM (switching on/off faster than human eyes can see) to reduce the power to the LEDs. Other dimming schemes are possible also.

You cannot control the dimming other than through the remote control because a smaller input voltage (for example 180 V AC) would be compensated for by the electronics. Or the circuit would just stop working properly.

The lowest setting at which the LEDs will work is determined by the design of the circuit that powers the LEDs. You can only influence the lowest setting by changing that circuit and that isn't something a beginner can do. It might not even be possible for an advanced engineer to do that as the components (chips) that are used might determine the lowest brightness setting.

So if you really need these lamps to output less light you will need to replace them with ones that have a lower light output (like 2 W instead of 5 W).

  • \$\begingroup\$ Great answer--practically impossible to address electronically but a quick fix with some small light filters over the lenses if you're willing to also live with a reduction in peak light output at 100% power. \$\endgroup\$
    – nvuono
    Aug 10, 2020 at 17:28

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