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February 4, 2020 09:22

I would like to make a Circuit to power an LED (but with different colour LEDs) using radio waves as a power source how can I do this ?

I want a circuit design for a wireless signal scavenger to power a low power LED. The principle frequency would be  from a normal home wi-fi  router signal. Is it possible to do this without a battery in the circuit, if not would a small hearing aid battery suffice.

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February 14, 2020 09:00

Are you thinking of those antenna LEDs that were popular on cell phones in the early 2000s, the ones that would flash briefly when they received a call? If so, you'll have your work cut out for you because even if you put this LED right on top of your Wifi router's antenna you will have a tough time collecting enough energy to light the LED. That's because the RF energy from the router is broadly distributed, both in frequency and in time - as in extremely short low energy pulses. It was far easier to make a tuned circuit to pick up on the burst of high power GSM signal transmitted by a 2G phone when it pinged the cell tower to let it know it was on the network. And even then, the LED was a brief, dim flash. If you're hoping to put this LED across the room from the router, you've *really* got a challenge on your hands.

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February 12, 2020 08:57

Ok, I'm no electrical engineer but you are walking down Mr. Tesla's path. The problem with using radio waves as a power source is that the energy transmitted falls off as an inverse square of the distance of the receiver to the transmitter. If what you want to do is power LEDs from broadcast RF then there are youtube videos on how to do it. essentially you construct an induction coil (antenna) sized to the target frequency and you should be able to meter potential at the ends of the antenna contacts. If you want to drive the transmitted power then using two parabolic satellite antennas so that you can contain the RF in a tight beam is an area of experimentation. Also look up masers for something truly dangerous. Just remember, if wireless power transmission was a thing there would be tech all over the place using it. And no wireless phone charging doesn't count because your phone's induction coil has to be within a millimeter of the transmitting coil. Any kind of distance and it's big energy time. Remember Tesla's big tower of doom. It went nowhere.

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February 11, 2020 08:56

I would guess that no one would come looking for you for stealing a little power from a radio wave. But, you should know that all radio waves have owners. The concept of charging a battery wirelessly is perfectly fine so long as it's after the electric meter. Just something to think about.

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February 12, 2020 08:55

@edempco just an FYI, No one 'owns' radio waves. Some broadcaster may own the content being transmitted and may have rights to the frequency on which it's being transmitted but the transmitted energy itself is unownable. As long as you do not interfere with the broadcaster's ability to transmit you can do anything you want with the 'radio wave energy'. Miniscule thought it may be.

February 7, 2020 09:01

It can be done, but the power levels are very low and you may get a glow from an efficient LED but I don't know how useful it will be as it depends on what you want the LED to do. Again a small hearing aid battery, well two in series unless of the 3V type will work but for how long is it required?
I tried to find some recent articles on wireless signal harvesting and there were a few, this probably gave the most information.
https://www.researchgate.net/publication/50282448_Investigation_of_RF_Signal_Energy_Harvesting but remember photos can be deceiving in how bright something appears! But the publication may help you in the details of the requirements.
Another article mentioned they generated 5V 10uA which indicates the area you will typically be working in.

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