# Electrical induction at a distance through coils for an LED night light

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.

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.

• 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. Nov 1, 2019 at 23:01
• @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. Nov 1, 2019 at 23:08
• the problem is you'll be lighting up other things than your intended coils. so, really, not feasible. Nov 1, 2019 at 23:23