I'm working on creating a compact RF energy harvester that's only a few inches wide, which would power an LED using only the ambient RF signals around us—like those from mobile towers, WiFi, and radio broadcasts. I'm totally avoiding any batteries, solar panels, or direct external power sources, and I also want to keep it aesthetic, avoiding rod antennas in favor of a coil design to mimic the look of an arc reactor. The goal is for the LED to stay dimly lit or pulse continuously. Is this even realistic, or am I aiming too high? I could really use some advice on the coil design, matching circuit, and diode choice. Has anyone here successfully lit an LED just from ambient RF?
3 Answers
You might want to focus on harvesting from local AM and FM stations, as they could provide stronger signals. It could help you get enough power to light up the LED, even if just intermittently. This doesn't guarantee success, but it's probably the best shot!
Honestly, I’d be surprised if you can keep an LED lit continuously without being near a strong transmitter. Ambient RF energy is usually really weak—typically just microwatts per square centimeter. To even see a faint light, you'd likely need at least a milliwatt of power. Pulsing it could lower the requirement, but you'd still need a Joule thief circuit or something to make it work. I'd recommend measuring the RF levels in your area to set realistic expectations!
You could potentially harvest energy with a coil and a capacitor, but you really need to tune your circuit to a specific frequency. For example, in urban environments, tuning to 2.4GHz can be effective since that's where many signals like WiFi are. Remember, you'll need to be relatively close to the source. There’s definitely multiple methods to achieve this, but that's the first approach that comes to mind!