Wireless power transfer project using 555 timer (having a problem with output voltage)

Donaire Carapichoso

Joined Oct 15, 2019
9
Good day.

Well I am building a Wireless power transfer project for a final year project undergraduate degree.
Im using a 555 timer to generate the frequency and I would like to get at least 10V at the output of the coil L3 (thats for charging purposes)

I'm having the required resonant frequency and a proper sine wave but the voltage is to low (7mV to be specific).
I would like to know, how can I raise it.

Here is the circuit diagram, I'm using NI Multisim version 13.
And please find attached the file for the simulation (frequency, oscillation and the output voltage)
Thank you

Thank you

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AlbertHall

Joined Jun 4, 2014
12,346
The high value of R6 is restricting the collector current of Q2 to around 1mA.
Try reducing the value (a lot), but make sure that Q2 doesn't get too hot.

ericgibbs

Joined Jan 29, 2010
18,849
hi DC,
Welcome to AAC.
The constant current limit resistor R6 in the emitter of Q2 is limiting the current to less than 1mA
E

Dodgydave

Joined Jun 22, 2012
11,303
Get rid of R6 and Q1...

Donaire Carapichoso

Joined Oct 15, 2019
9
The high value of R6 is restricting the collector current of Q2 to around 1mA.
Try reducing the value (a lot), but make sure that Q2 doesn't get too hot.
Thank you for the reply, I have reduced the R6 resistor value to the extreme of 100ohms even 39ohms but no change has been noticed (or better an it was 7mV and has got to 12mV)

AlbertHall

Joined Jun 4, 2014
12,346
How are you checking that you set the resonance frequency correctly?
Where are you measuring the 7mV-12mV?

Donaire Carapichoso

Joined Oct 15, 2019
9
hi DC,
Welcome to AAC.
The constant current limit resistor R6 in the emitter of Q2 is limiting the current to less than 1mA
E
Thank you for the reply, I have done changes in the R6 and even removed it but no increase in the output voltage.

Donaire Carapichoso

Joined Oct 15, 2019
9
How are you checking that you set the resonance frequency correctly?
Where are you measuring the 7mV-12mV?
Please find attached the screenshot of the simulation...
I have connected a Multimeter in parallel with the inductor L3, connected a frequency counter as well.

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Donaire Carapichoso

Joined Oct 15, 2019
9
Get rid of R6 and Q1...
Thank you, I have done that but no increase in the voltage.

AlbertHall

Joined Jun 4, 2014
12,346
The impedance of the chosen capacitor and inductor at the resonant frequency is about 3Ω. Try the circuit with, say, 370uH and 4nF.

ericgibbs

Joined Jan 29, 2010
18,849
hi.
Checking the resonant frequency with LTSpice I get this result.
What is your expected design freq at Resonance.?
E

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Donaire Carapichoso

Joined Oct 15, 2019
9
hi.
Checking the resonant frequency with LTSpice I get this result.
What is your expected design freq at Resonance.?
E
Thank you
I would require any frequency in the ranges of 130 kz- Mhz
So the result you got is right, the only problem will be the voltage which is too low.

The impedance of the chosen capacitor and inductor at the resonant frequency is about 3Ω. Try the circuit with, say, 370uH and 4nF.
Yes, I have tried the above values and still the same voltage.

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ericgibbs

Joined Jan 29, 2010
18,849
hi,
My tests sofar have not generated any resonant peak in your circuit.???
E

AlbertHall

Joined Jun 4, 2014
12,346
Thank you
I would require any frequency in the ranges of 130 kz- Mhz
So the result you got is right, the only problem will be the voltage which is too low.
With C2 as 1uF you won't get anything like 130kHz. 1nF would be nearer the mark.

Leeson

Joined Oct 14, 2019
1
And there's absolutely no way to amplify it to reach 130kHz?

Dodgydave

Joined Jun 22, 2012
11,303
Yes, I have tried the above values and still the same voltage.
Your tuned circuit is resonant at 130Khz, you need to increase the Frequency of the 555 to match the resonance, change C2 to 1nF, remove the 1Mpot, set the 5K to half way..

AlbertHall

Joined Jun 4, 2014
12,346
This circuit gives about 27V across L1.

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Donaire Carapichoso

Joined Oct 15, 2019
9
This circuit gives about 27V across L1.
Thanks a lot for your help, the voltage is has you said about 27V across L1... Thats is solved!!
As I'm not used to LTspice software, I'm finding a bit hard to perform the simulations (like to see the resonant frequency and so on).

Thank you

Your tuned circuit is resonant at 130Khz, you need to increase the Frequency of the 555 to match the resonance, change C2 to 1nF, remove the 1Mpot, set the 5K to half way..
Thank you , I have done that but no changes in the voltage as well.

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Donaire Carapichoso

Joined Oct 15, 2019
9
Good day!!

Here I go again. I'm building a wireless power transfer system (final year project) and testing different circuits to get the clue of it.
I came across a circuit, but i am not sure the wave I have got is a proper for this system.
I was supposed to get a sine-wave but instead the wave is saturated (if im not wrong), I would like to correct it.

The circuit is as follow, and please find attached the screenshot for the simulation (showing the wave i am talking about)
Thank you...

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AlbertHall

Joined Jun 4, 2014
12,346
C2 and L1 change values radically between your two diagrams. Which are you actually using?