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I have 3 decorative candle based night lights, and as an enthusiast project I decided to use LEDs instead of candles to modernize them and make them cooler.

enter image description here

I don't want to use batteries, and I want to be able to just connect them to a wall socket. Then it hit me that it would be way cooler to just place these lights somewhere, and have them emit light wirelessly if that's at all possible.

My reasoning was that LEDs generally require very little power and having these lights emit just a little light would be acceptable. Now I am not an expert at this, but I thought it was possible to implement.

So I want to have 3 coils connected to 3 LEDs in these lights, and have a single, bigger coil "base" powered through a wall socket underneath or behind these three. As the source is AC it should continually induce a current in the 3 light coils and keep the LEDs on.

So here are the parameters:

  • Source is 220V/50Hz
  • Max distance of each light from the source is 30cm
  • Everything else is variable. I am open to suggestions on what kind of LED or other light source to use, what kind of coil to use, etc.

And questions:

  • Is this practical at all?
  • How big should the coils be for each light, and the "base" coil?
  • Is it better to work with the 220v source, or use a transformer to bring down the source voltage and then have it flow through a coil? (Sounds a bit silly, I know)
  • What type of LED would be suitable for a current that can be induced at this distance?
  • Should I worry about other electrical devices close to the "source"? How do I protect them from the electromagnetic field?

Open to all ideas, thanks.

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    \$\begingroup\$ for any variable or non-very-close distance, this isn't really practical. "inductive power transfer" is just fancy for "a transformer, minus the core"; imagine how inefficient a transformer is if you moved the coils 30cm apart! You'll be better off with actually harvesting power. But: you need to start designing things somewhere. We can't tell you how dim an LED is still "bright enough", and we can't tell you how many hours per day your lamp needs to work. \$\endgroup\$
    – Marcus Müller
    Nov 1, 2019 at 23:01
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    \$\begingroup\$ @MarcusMüller I'm fine with inefficiency in this particular case. I may be wasting 100 watts to light up 3 small 0.2 watt LEDs and it would be fine. I am open to anything, because I don't know what kind of voltage I can get at this distance, so if anyone can calculate anything and give me an estimate that would be appreciated too. \$\endgroup\$
    – TheAgent
    Nov 1, 2019 at 23:08
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    \$\begingroup\$ the problem is you'll be lighting up other things than your intended coils. so, really, not feasible. \$\endgroup\$
    – Marcus Müller
    Nov 1, 2019 at 23:23

1 Answer 1

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For anyone interested, this YouTube video is a good resource for doing what I was asking. It shows you what you can achieve in practice, and is enough to answer almost all of my questions.

https://www.youtube.com/watch?v=4UmVLfFNx7U

It is completely feasible, you can do it safely with a simple transformer at typically low voltages and amps (9V to 12V @ 1A to 2A), a few coils, and a few LEDs. I'll post results after finishing the project.

EDIT:Another similar video: https://www.youtube.com/watch?v=Kj0dq8m_iBc

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  • \$\begingroup\$ Your example uses an oscillator. With the same complexity you could use the modern small scale Tesla coil variant named Slayer's Exciter. With it you could make fierce enough electric fields which make fluorescent lamps to glow. Search for it. Nikolai Tesla himself dreamed of practical global wireless electric power transmission. Tesla was a brilliant engineer, but he didn't understand radio waves which spoiled the system. \$\endgroup\$
    – user136077
    Nov 3, 2019 at 17:32
  • \$\begingroup\$ @user287001 You have to use one form of oscillator or another to create AC voltage out of DC and use of a single transistor to create an oscillator is straightforward enough. If I can find ready-made coils that would be great. Thanks for the tip. \$\endgroup\$
    – TheAgent
    Nov 3, 2019 at 17:46

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