Rectenna Lectenna Wireless Power Transmission

Wireless Power Transmission

To make a battery-less, wirelessly powered LED rectenna (Lectenna) energy harvester you just need a few components.

First you need a 1SS106 Diode, but this diode MUST have a little “H” on it for Hitachi. I bought a bunch of these little Schottky diodes that the eBay and Amazon listers said were made by Hitachi. I bought the “boutique” $5 diode from the UK. None of them had the little white “H” on them and so, none of them worked for this project.

Finally, I got fed up and started opening customer fraud complaints and a single dude on eBay (in China) said he had some “H” marked diodes and would send them. After 2.5 months of this I finally received a bag of these “H” diodes that actually worked. If you’re going to order off eBay or Amazon use the message function and tell the seller you must have “1SS106 Hitachi Diode with the white H on them” as nothing else will work. All the other 1SS106 diodes will fail to function! There are surface mount versions of similar diodes that will work, but they are literally smaller than the exclamation point at the end of this sentence and are super hard to pick up with tweezers is nearly impossible!

The other half of the circuit you need is a low CURRENT LED bulb. Just go on Digikey and get a bunch of Avago HLMP-D150 bulbs. They work, they are very low current, they are very cheap and they are red.

Ignore the two wires going to the old wifi router antenna (that's a later experiment). Notice how the flat side of the LED is OPPOSITE the banded end of the diode.

Again, notice how the flat side of the LED is OPPOSITE the banded end of the diode. Negative to positive.

Here's a pic of the two little guys twisted together. I put some dabs of solder at each end, only because I didn't want them falling apart when I took it around other people's gear.

Now what? Bend the legs of the red LED flat. This is your dipole antenna. It’s good at picking up microwave oven leaks and 2.45GHz wifi waves.

Next, put these two diodes (1SS106 & HLMP-D150) together so that the leg of the LED that has the flat side is connected to the side of the Schottky diode that has no marking. The LED has a leg near a flattened side. The Schottky diode has a leg near a banded end. You do NOT want these two legs to touch.

On diodes, one end will have a thick black or white stripe. The other end will have nothing. The end with the stripe is the NEGATIVE cathode wire. LEDs will have a flat spot on the base of the bulb or a shorter leg wire that means it’s the NEGATIVE cathode wire. FOR THIS EXPERIMENT WE WANT TO CONNECT ANODE TO CATHODE!!!!!  So we want the flat side of the LED connected to the NON-banded side of the diode.

You twist the two legs on one side together. Then the other.

Put this near a working router with 2.45Ghz (as opposed to just 5Ghz) band running and it will light up. I used an old Net Gear router that wasn’t hooked up to the internet. I just plugged the router into the AC wall outlet, turned it on then held down the padlock WPS button for a few seconds until the router went into the WPS easy connect mode which only then made the LED flash.

Lectenna in a dental floss container.

If you touch the metal wire legs of this energy harvester, you’re actually touching the antenna. This will make the light go out. So, you can try holding it by the bulb or just find a little plastic tube or bag or better yet just tape it to a piece of paper or a wooden stick and then you can poke it all around different equipment: routers, older cellphones, leaky microwave oven doors, etc.

On my Xfinity Arris “gateway” that is a modem and wireless router combined it blinked and lit up, but not as much. You have to lay it right on top of the bridge, near the rear of the box.

The best way to light these was one of those white TPLink Wi-Fi extenders that look like a kid's nightlight.

Someone was throwing away a BUNCH of wifi routers and they gave me about a dozen of this little black detachable, 90-degree bendable wifi antennas. I’m going to attach one of those antenna’s to this device to see if I can get farther away and still have the bulb light up. Right now it has to be touching either of the routers to light up, and it has to be in the correct spot on the router too!

There are a lot of ways of making a rectifying antenna (rectenna). Most involve intricately cutting tiny, flat sheets of copper into square cutout maze-like shapes. A Hitachi Schottky diode is easier: just make sure it has the “H” on it.

There are a lot of ways of proving your rectenna is working. Most involve satellite dishes and frequency analyzers and tons of fancy equipment. This way just blinks an LED for you to see it’s working.

I bought from China eBay user Hifiic and initially got Schottky diodes without the “H” on them and they didn’t work. I left feedback (negative, my first ever negative) about counterfeit. The dude(?) sent me a bag of real ones with the “H” and those were the only ones that worked. If you order from them, in the message to seller on the order page make sure you say “HAS TO BE “H” ON THE DIODE OR ELSE IT WON”T WORK!!!!” and they’ll hook you up hopefully. The UK seller LittleDiode sent me something which also didn’t work for way, way more money. To be fair, this is an oddity in the diode market: it’s the right case and product number, but only the older “H” diodes will work.

I also bought some smaller, surface mount diodes that should theoretically work, but they are so, so, so tiny I can barely see them. I would have to solder them because they are rectangles with pads (no wire legs sticking out) so I’d need to by one of those ultra-thin soldering irons with the microscope attached to even work with these. I’ve seen people take the insulation of a thin copper wire and pull the copper strands apart and then solder that tiny single copper strand (the width of a human hair) onto a surface mount diode.

That’s how they make fingernail NFC powered LED lights: seriously, they’re even smaller and they are glued to a person’s fingernails and they are lit up by the NFC (near field communication) waves coming out of a cellphone (you know: the “tap” to pay thing). Crazy blinking lights on your fingernails!!!! I have some of those (cheap from Amazon) and I have a test/development board NFC USB reader device ($10) coming that will hopefully light them up—since my current phone doesn’t have NFC. Which is probably a good thing: I can’t imagine not passing by a vending machine if I had tap-to-pay on my phone. Plus, I’m a dude so it’d look weird if I glued this microchip lights onto my fingernails.

I'll update later, there is a vicious thunderstorm happening now.