You Say Wireless Power, I say Evanescent Wave Coupling.

Because that’s what it is and it sounds so much cooler!  In this quick hack I managed to power the Christmas lights on the balcony by transmitting the power through the glass door rather than leaving it open with a cable leading out there.

So it’s coming up to Christmas now (you can tell because the supermarkets have started putting up their easter specials) and, while I sit here in my nice cosy lounge finishing the caviar and a glass of Chandon, I ask myself if I could be any more decadent.  Perhaps I should get some Christmas lights out on the balcony and leave them on all night to show the neighbours how much more electricity I can afford to waste than they can. <end sarcasm>.


I would like to have some lights on the balcony though, if only a few, but there are no power outlets there and the idea of leaving the door open all night so I can sling an extension cord out there seems a bit silly.  Since I can’t be trusted with power tools, drilling a hole or installing an outlet is off the cards too.  What am I to do?

Why not just push the power through the glass door!?

Simple enough.  Push power in from one side and collect it on the other.  If you’ve got the image of some wires gaffa taped to the glass and think it’s ridiculous, you’re right.  I tried, it doesn’t work and the neighbours now think I’m weird.  But let’s take a look at a working model of what we want to achieve.  For example, the wireless charging for my mobile phone goes through the plastic casing of both the phone and the charger.  There’s not much power going through there, but it’s enough for a sanity test.  Fortunately I’ve got a spare wireless charge circuit or 2 laying around that I bought for about $5 each from Bangood a while back.

Wireless Charger Circuit

Now I wasn’t fond of that wire crossing over the coil and thought it would sit nicer against the glass if I just gently drilled a hole through the plate and passed the wire around the back.

Broke it

Did I say gently?  I meant almost put a drill through my thumb as that brittle little bastard shatters in the first second of drilling.  So not the best execution, but it still achieves the goal and I was able to route that wire around the back.  A little double sided tape to secure it to the glass door and we’re ready for a quick test.

Charger in place

Throwing my phone up against the glass outside yielded a successful coupling and the phones started charging fine.  Next up is adding our intended load to the circuit.  Some Christmas lighting.  I had a string of fairy lights that run off 3 volts, so the charge circuit should be able to light those up pretty easily.

Fairy Lights

To get the power to the lights, I harvested the receiving coil from a broken Nexus 5 case.  It’s a simple as cutting the battery pack off the fairy light string and soldering the lights onto the receiving coil terminals.

Coil and Lights Connected

Pretty obvious what to do next.  Stick that to the outside of the glass door over the transmitting coil

Everything In Place

And finally power that sucker up.


Booyah!  Pretty damn simple.  Power transmitted through the glass to power the outside lights.  The door stays closed and locked and I get lights outside.  Now I have to admit I threw this together pretty quick so it’s not perfect.

As you can see, the lights are flickering and they’re actually not supposed to.  This could possible be that the glass is too thick or I damaged the transmitting coil more than I thought when I tried to drill through the plate.  Either way, it’s looking to be running low on power.  But it proves that it can be done and merely needs to be done with more care and the correct value coils etc. for the application.

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