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AEM40940 – Energy Harvesting Power Management IC
Anybody have experience running a prop with one of these
Looking for input on how efficient it is and distance it has to be from wireless source to be of any use. Does it have to be within 10 feet of Wi-Fi hub etc..
The inverse square law will make it drop off pretty fast. An isotropic radiator that generates 100mW (e.g. wifi router) would have a power density at 10 meters of approx.
0.1 / (4 pi 10^2) = 80 microwatts per m^2. That's about -11 dBm, compared to the stated -17dBm limit of the aem10940 device. Still, even if it can extract 80 microwatts, that amount of power is potentially only enough to operate a Prop 1 in RCslow (3 volts * 5 microamps = 15 microwatts).
There was company at the Sensors Expo in San Jose last month that had an impressive demo running a bright LED on harvested RF. The LED and a couple of other parts was mounted on a board about 12cm longish if I remember correctly.
edited July 18
All sounds a bit scammy to me.
Sure you can move energy around using RF. That is what radios do.
As Tracy points out the energy available becomes very small very rapidly with distance.
The antenna is as important as any high efficiency chip connected to it.
I notice the demo at the sensors expo is a 12cm or so antenna in very close range to the transmitter. Kind of a party trick.
, Did you say 80 microwatts per m^2 ?
I'd love to see a Propeller powered from a WiFi router 10 meters away. Even with a 1 meter square antenna array !
My current project is based on the prop running with RCslow on three AAA batteries. I'm 7 months in to testing and all is going as planned to make the calculated run time (goal is 1 year). I was wondering if something like this could extend the run time 5 to 10 years. I want to keep my off the shelf lithium batteries. I have been thinking about adding this as a primary power source and only go to the batteries when no RF energy is available. Sounds like it would be very hard to predict how efficient this would be since it must be so close to the RF source. I still my experiment with it once I get this version wrapped up. Thanks for the input!
Perhaps an antenna tuned to AM or FM broadcast station might be more versatile? They certainly show up
on an RF spectrum analyzer readily if any old bit of wire is coupled to its input.