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Is it possible to step up the voltage of square wave ac coming out of a function generator from 5ppv around 10ppv? Answered

I'm trying to use a square wave function generator for the purposes of inductively charging a cell phone. Also, would magnetic shielding be necessary for this application or is the magnetic field weak enough to not interfere with the phone?

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steveastroukBest Answer (author)2009-07-22

I'd use a power amplifier to do what you want since a signal generator isn't going to be too happy driving a transformer with a realistic amount of power.

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user

Sorry but I'm a bit of an electronics newb and confused as to how to use the power amplifier. How does the signal generator have two outputs while the amplifier only has one?

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user

Sorry, I don't see what you mean. A power amp has TWO sets of terminals, the inputs and the outputs. The input goes to the output of the signal generator, the output goes to the load

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user

I'm looking at the LM386 Low Voltage Audio Power Amplifier datasheet as an example. There is one positive input and one negative input, which doesn't make sense to me considering that in AC the positive and negative sides flip constantly. Also, there is only one V-out pin. Thanks for helping.

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user

What frequency are you intending to drive this thing at ? Will a 386 audio amp be good enough ? You'll get improved performance driving this thing with sine wave BTW.

This site has a typical example circuit.,
http://www.hobby-hour.com/electronics/lm386-power-audio.php

You can see how the inputs are connected. The - input is usually grounded in these circuits, though there are arrangements when you don't.

The maximum O/P power is 1W into 32 Ohms with a 12V supply.

Only you know what you need.

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user

I think that most of my confusion comes from my lack of an understanding of AC. Coming from the function generator, is the current of the square wave "on-off-on-off" rather than "forwards-backwards-forwards-backwards"?

I'm somewhat basing this project on the instructable by robotkid249: https://www.instructables.com/id/Wireless-Power-Transmission-Over-Short-Distances-U/

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user

What come out of the function generator is still AC. Where do you have the concept of forward/backwards ? Steve

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user

dictionary.com definition-

alternating current
–noun
an electric current that reverses direction at regular intervals, having a magnitude that varies continuously in sinusoidal manner.

Thanks.

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user

I see. What you have from a ground referenced signal generator can be either with a DC bias, or swept around ground - it depends on the design and configuration, you may well want both DC offset and zero offset signals for some tests. From the point of view of the amplifier it doesn't care,provided there is a DC blocking capacitor at the input. The coil must never have DC in it.

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user

What frequency are you intending to drive this thing at ? Will a 386 audio amp be good enough ? You'll get improved performance driving this thing with sine wave BTW.

This site has a typical example circuit.,
http://www.hobby-hour.com/electronics/lm386-power-audio.php

You can see how the inputs are connected. The - input is usually grounded in these circuits, though there are arrangements when you don't.

The maximum O/P power is 1W into 32 Ohms with a 12V supply.

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user
orksecurity (author)2009-07-21

Stepping up a voltage requires either an amplifier or a transformer. The amplifier required a higher voltage available to be controlled by the lower voltage, the transformer increases voltage but reduces amperage. Of course the induction coils essentially are a transformer (though a lossy one)... if you get the ratio of number of turns right you should get the voltage you need but (again) may not get enough current.

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