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Registered Member #2860
Joined: Sun May 16 2010, 06:59AM
Location:
Posts: 5
Hi all, I'm working on Witricity and there is a problem. When I try to put a second multi-turn copper ring near the single turn source coil, system performance becomes even worse. I have no idea what to do. Could someone can help with me ? I have a photo that one multi-turn copper ring is working as follow
Registered Member #531
Joined: Sat Feb 17 2007, 10:51AM
Location: Burlington, Vermont
Posts: 125
zxshow wrote ...
Hi all, I'm working on Witricity and there is a problem. When I try to put a second multi-turn copper ring near the single turn source coil, system performance becomes even worse. I have no idea what to do. Could someone can help with me ? I have a photo that one multi-turn copper ring is working as follow
It's not entirely clear to me what your setup / question is but... Bear in mind that the technique is nothing more than link coupled high Q resonators. Ignore the obtuse approach that the MIT group took to explaining the operation, it will simply confuse things.
The MIT group had two resonators - one resonator was loosely coupled to the single turn 833A power oscillator, the other resonator was loosely coupled, also via a single turn I believe, to the lamp (load). The resonators were, in turn link coupled to one another. Think of it as dual Tesla coils in which the secondaries are magnetically coupled to each other.
Registered Member #2860
Joined: Sun May 16 2010, 06:59AM
Location:
Posts: 5
scott fusare wrote ...
zxshow wrote ...
Hi all, I'm working on Witricity and there is a problem. When I try to put a second multi-turn copper ring near the single turn source coil, system performance becomes even worse. I have no idea what to do. Could someone can help with me ? I have a photo that one multi-turn copper ring is working as follow
It's not entirely clear to me what your setup / question is but... Bear in mind that the technique is nothing more than link coupled high Q resonators. Ignore the obtuse approach that the MIT group took to explaining the operation, it will simply confuse things.
The MIT group had two resonators - one resonator was loosely coupled to the single turn 833A power oscillator, the other resonator was loosely coupled, also via a single turn I believe, to the lamp (load). The resonators were, in turn link coupled to one another. Think of it as dual Tesla coils in which the secondaries are magnetically coupled to each other.
You appear to have a single resonator?
Regards
Scott N2BJW
Really thank you. But I still don't know how to do. Could you discribe in details or send me some information to study ?
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
zxshow wrote ...
Grenadier wrote ...
So if I'm understanding you correctly, when you add another coil the lamps get dimmer? That just sounds like loading to me...
Yes that's right! Mit guys use two multi-turn ring. According to mu results, only one is needed.
Hi zxshow,
In short, just putting random coils of wire near your transmitter and receiver side is ofcourse pretty unlikely to do any good at all. The coils are resonators that have to be tuned just like tesla coils. The reason you seem not to need another helical resonator near the transmitter is that you already have one - it's the output tank circuit of whatever tube oscillator you're using - and it's capable of carrying enough reactive power to make your oscillator alone a formidable wireless power-transmitter. You could change the parameters of it's tank circuit for impedance matching (more turns, less capacitance) to get the Q and power throughput higher, but it's generally considered easier to magnetically couple another resonator to the first one to perform this job.
You need to consider though that putting those two resonators in close magnetic coupling will make whole oscillate at a completely different frequency, and this system will not anymore be in tune with your receiver! Hence you'll need to re-tune your receiving resonator by adding more turns or compressing it up so it's f0 goes lower. I'd also advise to try using a few-turn coil with a tap (aligator clip or etc.) for your light bulb and play with the tap a bit until you find the bright spot.
Registered Member #2860
Joined: Sun May 16 2010, 06:59AM
Location:
Posts: 5
Marko wrote ...
zxshow wrote ...
Grenadier wrote ...
So if I'm understanding you correctly, when you add another coil the lamps get dimmer? That just sounds like loading to me...
Yes that's right! Mit guys use two multi-turn ring. According to mu results, only one is needed.
Hi zxshow,
In short, just putting random coils of wire near your transmitter and receiver side is ofcourse pretty unlikely to do any good at all. The coils are resonators that have to be tuned just like tesla coils. The reason you seem not to need another helical resonator near the transmitter is that you already have one - it's the output tank circuit of whatever tube oscillator you're using - and it's capable of carrying enough reactive power to make your oscillator alone a formidable wireless power-transmitter. You could change the parameters of it's tank circuit for impedance matching (more turns, less capacitance) to get the Q and power throughput higher, but it's generally considered easier to magnetically couple another resonator to the first one to perform this job.
You need to consider though that putting those two resonators in close magnetic coupling will make whole oscillate at a completely different frequency, and this system will not anymore be in tune with your receiver! Hence you'll need to re-tune your receiving resonator by adding more turns or compressing it up so it's f0 goes lower. I'd also advise to try using a few-turn coil with a tap (aligator clip or etc.) for your light bulb and play with the tap a bit until you find the bright spot.
Marko
Thanks Marko. Your suggestions really give me some new ideas ! I didn't make any Tesla coils so I don't know how to tune it. "You could change the parameters of it's tank circuit for impedance matching (more turns, less capacitance) to get the Q and power throughput higher, but it's generally considered easier to magnetically couple another resonator to the first one to perform this job. " I don't understand wht's this mean?
I'm still not clear the role of the two multi-turn coil. The receiving one can carry more reactive power than single turn. However, the other one near the source seems to be redundant.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
i did recall reading somewhere that one major problem with WiTricity is proximity effects on the transmitter. AFAIK there is a workaround, but it would require tuning the RX tank as well which doubles the complexity.
Interestingly, one possible option is waveshaping, by using lots of small highly directional coils and slightly altering the relative phasing like a PA radar system or ultrasound, the field could follow the RX around a room without actually moving the coil (!) i think a similar system is used on some WiFi access points being sold now.
-A "Bother!" said Pooh, as the Phoenix failed to enter Warp...
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I'm working on Witricity and there is a problem
