# Increase frequency of AC voltage

Discussion in 'The Projects Forum' started by terrycpl, Jan 21, 2010.

1. ### terrycpl Thread Starter New Member

Jan 12, 2010
11
1
I am making a Circuit to increase the frequency of AC sinewave voltage with 50 hz.

How Can I increase it from 50 Hz to 80 Hz or above without change the shape of sinewave? (the input voltage is around 5VAC)

Is It using the R,C Circuit?

2. ### 3ldon Active Member

Jan 9, 2010
82
3
it may be best to make a frequency to voltage converter followed by a voltage to frequency converter. because the frequency is so low, it would be cheaper as far as parts count to just hook up a zero crossing detector to a micro controller and use a lookup table to generate the sine wave from PWM.

3. ### terrycpl Thread Starter New Member

Jan 12, 2010
11
1

I never use the voltage to freq converter before.
As the input is 5VAC sinwave with 50Hz, it is a AC voltage, and I found that many VFC is only for DC input. Any suggestion IC is good for AC input?

Also, If I want to get the same output voltage , 5VAC but with high freq and above 80Hz, can I get this?

Thanks,
Terry

4. ### Ron H AAC Fanatic!

Apr 14, 2005
7,012
681
Why do you need this? The solution to your problem depends on your application.

5. ### DC_Kid AAC Fanatic!

Feb 25, 2008
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does it need to be clean snewave? i would think a full wave rectifier, chop it at 80Hz, couple it back out to AC. so as others have asked, why do you need 80Hz, whats the application? what's the dependence on the 5vac source?

6. ### terrycpl Thread Starter New Member

Jan 12, 2010
11
1
The final result is to get the Sinewave 5VAC with 80Hz or above.

At the begining , I have a 220VAC with 50Hz,
what I want is to
1. increase the Freq to at least 80Hz without change the shape of sinewave
2. the voltage is decreased to 5VAC.

If using the rectifier, the freq is doubled but it is not sinewave..

I wanna to use the transformer to derease the voltage from 200AVC to 5VAC , then find the analog mulitipler IC AD633 before and want to use multiplication to get higher freq then use AC/AC converter to decrease the voltage again
However, I find that the opearating voltage of this IC is too large for me ,
so, any suggested IC has similiar function with lower opearating of AD633?

Or any method to increase the freq without chnage the shape of sinewave?

I have no time...

Thanks
Terry

7. ### beenthere Retired Moderator

Apr 20, 2004
15,808
295
Can you clarify something? This signal is really in no way related to your line voltage, correct?

This statement is very hard to interpret.

It would be helpful to know:

1. What is the intended use of this waveform?

2. You may mean that you wish to increase the voltage after increasing the frequency. What is the final signal voltage?

3. Is the use of an AD633 absolutely necessary?

8. ### terrycpl Thread Starter New Member

Jan 12, 2010
11
1

Yes..you are correct...Maybe I get the wrong concept to use the AD633 as it only double the signal, not the voltage..and the output current is too low of using this IC...

My project is just to increase the freq of the input sinewave voltage(220VAC, 50Hz) to 80Hz or above......
I think it is the field of power supply, I need to construct a circuit to increase the freq the output sinewave voltage (as the voltage is decreased to 5VAC by using the transformer)

It is the field of power supply...maybe just use some R,C,L....
but I don't know what circuit should be used...
as I find some books..it just tell me the phase shfit of the A.C sinewave or the delay of the sinewave, I didnot find any information what related how to increase the freq of AC voltage....

9. ### THE_RB AAC Fanatic!

Feb 11, 2008
5,430
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You still have not answered the question.

What will the 5v 80Hz be used for? What does it power?

10. ### terrycpl Thread Starter New Member

Jan 12, 2010
11
1

LED lighting, as 50Hz will make the LED flash, but increased to 80Hz, the LED will not flash.
The book I found is only phase shift of the sinewave..not increase the freq....
No reference I can find...

highvoltpower likes this.
11. ### beenthere Retired Moderator

Apr 20, 2004
15,808
295
LED's are DC devices. using a transformer to step the line voltage down to a lower level and rectifying to DC would make a much better source. Some means has to be used to limit current through the LED's as well. For varying the intensity, pulse width modulation of the current is effective.

Tells us all about the LED's - forward voltage and required current, as well as number to be used.

12. ### terrycpl Thread Starter New Member

Jan 12, 2010
11
1
However, I have no choice..
my supervisor only need me to increase the freq of the sinewave..

as I know the LED he provide is 20mA with around 3.5V , and he want me to power up around 100 LED...

But now, the main problem is how to increase the freq..
I have no direction..

13. ### Ron H AAC Fanatic!

Apr 14, 2005
7,012
681
With all due respect, unless this is an educational exercise, your supervisor doesn't know what he's talking about. You need to tell him, as tactfully as possible, that the simplest solution by far is to convert the 50Hz AC to DC. You will have to do that anyway, regardless of the frequency of the source, because LEDs will only pass current in one direction.

14. ### THE_RB AAC Fanatic!

Feb 11, 2008
5,430
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Use 4 diodes as a bridge rectifier, then the LEDs will flash at double the frequency, ie 50Hz -> 100Hz.

And I agree with Ron_H.

15. ### Ron H AAC Fanatic!

Apr 14, 2005
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That's what I was thinking. It's DC with AC superimposed on it, or stated another way, pulsating DC. He probably doesn't really need to filter it for his application.

16. ### t06afre AAC Fanatic!

May 11, 2009
5,936
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Also the human eye will not se any blinking on the LEDs, but a constant light. The 80 Hz may appear somewhat more bright than the 50 Hz, nothing more than that

17. ### Ron H AAC Fanatic!

Apr 14, 2005
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80Hz flicker is generally not detectable by the human eye. 50Hz is noticeable and objectionable to some people.

18. ### studiot AAC Fanatic!

Nov 9, 2007
5,003
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The traditional way to produce a variable frequency power supply of modest capacity is to use an audio power amp as an oscillator. You can get up to a couple of hundred watts this way quite easily. A wein bridge configuration with a modular power amp is suitable. Power this from your 50Hz supply.

19. ### Ron H AAC Fanatic!

Apr 14, 2005
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If he does it, Rube Goldberg will be proud.

20. ### Bernard Expert

Aug 7, 2008
5,114
586
Use a phase -locked loop. Square up the 50 Hz to a square wave. The PLL [LM565], has a voltage controlled oscillator which will multiply, with proper components,the 50Hz to 400 Hz, use divider to divide by 5 giving 80 Hz. Dividing by 8 gives Almost 50 HZ which is comared to origional 50Hz & generating a correction V to VCO to make divided down 50 Hz exactly same as origional, the 400 HZ then is then also exact, giving an exact 80 HZ square wave. Use class D amp to give desired operating voltage & filter. LED current limiting resistors can be part of filter. Use a high V out [48V], to shorten the number of LED strings. At least I think that is how it works.