- #1
md5fungi
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I'm part of a Senior Design project involving Wireless Energy Transfer. We are trying to power a standard red LED as a demo, via resonant inductive coupling. Our setup is as follows:
We have a 40.64 cm diameter transmitter coil (magnet wire) with 6 turns, hooked up to a signal generator. Our receiver coil has a 2 cm diameter, with 21 turns. We measured the respective resonant frequencies of these two coils, and used 522 pF of equivalent capacitance in parallel with our load (LED) to tune the receiver's resonant frequency to match the transmitter's.
We placed the receiver coil inside the transmitter coil on a table with our signal generator at the resonant frequency. The result was a very very dimly lit LED, and it became brighter when we moved the receiver coil outwards, i.e closer to the transmitter coil. When we look at the output waveform on an oscilloscope, we get ~ 5 V peak-to-peak, and when we rotate the receiver coil so that it is perpendicular to the transmitter coil, the amplitude drops quite a bit, which seems to indicate that resonant inductive coupling is occurring.
The thing is, we're not quite sure why the LED is barely lit. Adjusting the capacitance on our receiver coil does not seem to help, and changing the frequency only makes it dimmer. We are guessing that very very little current is going through our LED, which is why 5 V does not suffice to turn it on. We have tested the LED by hooking it up directly to the signal generator, and it lights up quite brightly.
Any ideas why we are getting such poor efficiency? Even when the receiver coil is very close to the transmitter the LED barely lights up...
Note: We got the LED to bright up very lightly when untwisted the twisted pair of alligator clips we used to connect the receiver coil to the LED. This would seem to indicate that the alligator clips were forming a loop and coupling with our other two loops, however, and that is not what we want.
This is our setup. We've tried this with and without that resistor, we just did that because we thought it might increase the Q:
We have a 40.64 cm diameter transmitter coil (magnet wire) with 6 turns, hooked up to a signal generator. Our receiver coil has a 2 cm diameter, with 21 turns. We measured the respective resonant frequencies of these two coils, and used 522 pF of equivalent capacitance in parallel with our load (LED) to tune the receiver's resonant frequency to match the transmitter's.
We placed the receiver coil inside the transmitter coil on a table with our signal generator at the resonant frequency. The result was a very very dimly lit LED, and it became brighter when we moved the receiver coil outwards, i.e closer to the transmitter coil. When we look at the output waveform on an oscilloscope, we get ~ 5 V peak-to-peak, and when we rotate the receiver coil so that it is perpendicular to the transmitter coil, the amplitude drops quite a bit, which seems to indicate that resonant inductive coupling is occurring.
The thing is, we're not quite sure why the LED is barely lit. Adjusting the capacitance on our receiver coil does not seem to help, and changing the frequency only makes it dimmer. We are guessing that very very little current is going through our LED, which is why 5 V does not suffice to turn it on. We have tested the LED by hooking it up directly to the signal generator, and it lights up quite brightly.
Any ideas why we are getting such poor efficiency? Even when the receiver coil is very close to the transmitter the LED barely lights up...
Note: We got the LED to bright up very lightly when untwisted the twisted pair of alligator clips we used to connect the receiver coil to the LED. This would seem to indicate that the alligator clips were forming a loop and coupling with our other two loops, however, and that is not what we want.
This is our setup. We've tried this with and without that resistor, we just did that because we thought it might increase the Q: