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Miniature wireless power demonstrator

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Elecric eng

Tue Nov 02 2010, 12:49PM

Registered Member #3354 Joined: Sun Oct 24 2010, 09:48AM
Location: Tulkarm-Palestine
Posts: 10

Hi guys,

I fixed the problem with the relay ( by shorting between common pin and NC pin )and the led switched on .. but h still have no currant driven by the source !!
really I need your help .. any advice??

dustinthwnd

Fri Nov 05 2010, 07:48PM

Registered Member #3397 Joined: Fri Nov 05 2010, 07:36PM
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Posts: 1

Hey Marko,
I am trying to reproduce what you have made, but I wanted to first start with the simple, old circuit diagram.

I am very very new to this stuff but was wondering if you could help:

1). What do the MOSFET's and diodes do in the circuit?

2). What are Ugg and Udd exactly?

3). What is the circuit grounded to?

Thanks in advance!

Elecric eng

Sun Nov 07 2010, 09:43AM

Registered Member #3354 Joined: Sun Oct 24 2010, 09:48AM
Location: Tulkarm-Palestine
Posts: 10

Elecric eng wrote ...

Hi guys,

I fixed the problem with the relay ( by shorting between common pin and NC pin )and the led switched on .. but h still have no currant driven by the source !!
really I need your help .. any advice??

hello everyone,
I replaced my Mosfets with another ones .. but this time the citcuit drawn very high currnt from the power supply and both Mosfets heated up quickly !!
what would mosfets heat up while it could handle 50 A as recorded in the datasheet??

Thanks again ..

hanys

Mon Nov 08 2010, 01:34PM

Registered Member #3307 Joined: Tue Oct 12 2010, 12:18PM
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Posts: 4

There is no way the mosfet could handle 50 A!! 12V x 50A gives 600 W while the max power dissipation of transistor (irfn44) is 110 W. with 50 A it would melt in less then a second. You would heave a perfekt cooling system with it possible only in laboratory conditions. No radioator with FAN cooler would help

kiat

Tue Nov 09 2010, 12:52PM

Registered Member #2115 Joined: Fri May 08 2009, 01:17PM
Location: Singapore
Posts: 46

the fets have a drain-source ON resistance, so power dissipated = Id^2*R(ds)on. But anyway, semiconductors very rarely run close to their rated current ratings due to overheating.

In the circuit the mosfets should only switch a few amps at most- very far away from 50 amps.

Elecric eng

Thu Nov 11 2010, 09:38AM

Registered Member #3354 Joined: Sun Oct 24 2010, 09:48AM
Location: Tulkarm-Palestine
Posts: 10

hanys wrote ...

There is no way the mosfet could handle 50 A!! 12V x 50A gives 600 W while the max power dissipation of transistor (irfn44) is 110 W. with 50 A it would melt in less then a second. You would heave a perfekt cooling system with it possible only in laboratory conditions. No radioator with FAN cooler would help

kiat wrote ...

the fets have a drain-source ON resistance, so power dissipated = Id^2*R(ds)on. But anyway, semiconductors very rarely run close to their rated current ratings due to overheating.

In the circuit the mosfets should only switch a few amps at most- very far away from 50 amps.

I see ...
My Mosfet rated power is only 50W ... which mean that only 3-4 amp max current could pass it .. but as Marko said that about 20A comes to the coil loop .. is this mean that i need mosfet with higher rated power (110W as hanys said) to solve the problem of mosfets heating (of course also using heat sinks)???

kiat

Thu Nov 11 2010, 02:24PM

Registered Member #2115 Joined: Fri May 08 2009, 01:17PM
Location: Singapore
Posts: 46

The area where high current circulates is between the caps and the copper pipe in a parallel resonant LC tank. It presents a high impedance to the mosfets so power only flows when power is wasted in the LC tank. (eg the light bulb can be seen as a parallel resistor since its coupled to the transmitter coil). So when the light bulb is disconnected the only power that flows is the power needed to overcome the resistive losses in the LC tank.

Hence, the mosfets will only carry current when a load is seen by the transmitter coil. At most a few watts if your just driving some bulbs.

tzyy

Fri Nov 26 2010, 05:22AM

Registered Member #3443 Joined: Fri Nov 26 2010, 05:13AM
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Posts: 1

Hello guys

First of all, nice project you did that Marko. Your youtube video is nicely done.

I'm currently working on a wireless energy transfer project too. My design will be transmitting energy at 10Mhz(similar to MIT's idea) but in much simpler design. I've not construct any circuits in real yet but I've basically designed the whole idea.

My Colpitts Osillator design will be using: (

with C1 and C2= 5.6pF, L=9.09x10^-5 (r=0.3m, a=3mm, N=6).

I have seen a lot people designing with low frequency(~1Mhz), but I'm aiming for a bigger transmission range. I have not decided which transistor I should use as I'm not familliar with Colpitts Oscillator and there's limited source out there.

Does anyone has any clue what kind of transistor should I be using to achieve a 10Mhz circuit? MOSFET has a limit of ~2Mhz that's why I've to look into Colpitts Oscillator.

Feel free to give me some suggestions or point out any difficulties I will be facing with this design as I'm still at the begining stage of the project.

Thanks :)

Zxdave10

Wed Feb 02 2011, 05:44PM

Registered Member #3664 Joined: Wed Feb 02 2011, 05:35PM
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Posts: 1

Hello, Im doing a similiar project to marko and strider(more like strider). I used a network analyzer to discover the resonant freq of the coils. I am trying to use an impedence analyzer to find the characteristic impedance of each coil. Has anyone ever used empro to model wireless power? I am new to using empro and am having some issues.
Thanks

epilot

Wed Feb 09 2011, 01:10PM

Registered Member #2986 Joined: Fri Jul 09 2010, 10:17PM
Location:
Posts: 1

Hrello Marko,

Just have a question for you please.

I want to gather the stuff of your design (That's a really nice job thanks for sharing it) and make a such device.

But my question:
Is your circuit (shown at post NO 1) capable to lighten just 4 or 5 LED's at a distance of say 1 meter?

Thanks beforhands

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