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Old 15th November 2011, 03:38 PM   #1
graygem is offline graygem  United States
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Default Schematics needed for 3V 1KHz Sine wave generator

Would like a 1KHz sine wave tone generator that would run off a 3v rechargeable lithium coil cell battery. All the ones I found were for 9V plus. The idea was to make a USB chargeable tone generator using a New Age USB enclosure Any help would be appreciated.
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Old 15th November 2011, 05:56 PM   #2
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I think that your are not getting replies because the question is so open ended. I would ask -- do you really only want only one frequency? What is the desired output level and into what impeadance? Does it need to be a spectrally clean signal? Does it need to be frequency stable and accurate? The first thing that comes to mind is a one transistor LC based oscillator perhaps with a buffer. Of course the physical size of the L and C are going to make it hard to get into any of those boxes. The other approach if you need accurate frequency is to run a crystal oscillator at some higher frequency and then divide it down, but that involves a flip flop or some such which sill output a square wave and then you could filter out the harmonics,. I would consider a small microprocessor like a PIC. There are probally some that could be programed to do the frequency division with onboard logic. All of these options can be designed to operate off of your 3V, but you have 5V when connected to USB. Do you mean that this should be able to operate stand alone after charging? In short, tell us more about what your are trying to acconplish. I must be bored to write a reply like this.
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Old 15th November 2011, 06:09 PM   #3
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Oh Yea Check out Audio Test Oscillator
Rod Elliott has some nice clear information on the subject.
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Old 15th November 2011, 06:23 PM   #4
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http://www.discovercircuits.com/Andy...oscillator.pdf

But use a rail to rail low power op amp. Also you will need an output coupling capacitor.

http://www.ti.com/lit/ds/symlink/opa2342.pdf

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Old 15th November 2011, 06:34 PM   #5
jcx is offline jcx  United States
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DAP, the ubiquitous portable "mp3" players are what comes to mind 1st for me

they already have usb, battery charging, user interface, can hold quite a few more test waves than just 1 kHz sine
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Old 15th November 2011, 07:08 PM   #6
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Quote:
Originally Posted by jcx View Post
DAP, the ubiquitous portable "mp3" players are what comes to mind 1st for me

they already have usb, battery charging, user interface, can hold quite a few more test waves than just 1 kHz sine
Now that is a good idea.
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Old 17th November 2011, 12:30 AM   #7
graygem is offline graygem  United States
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Yes, I only need the one frequency, 1KHz. It is for a tone test on induction loop equipment. We've tried using an MP3 player but the conversion from the test CD changes the tone so it is not an accurate reproduction of the 1KHz tone. I have used my iphone but I really don't want to lend that out, plus the output is not quite high enough before distortion kick in. My thought was to have a tone generator that could easily be recharged through USB. When it's charged, it could be taken to the site for test. I could be easy on myself and build a 9v tone generator, but what's the fun in that.

I have already been to Mr Elliot's pages.
I Will look into Simon7000's links, thank you.
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Old 17th November 2011, 12:52 AM   #8
jcx is offline jcx  United States
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Default if you're fixated on hacking analog, fine - but the DAP will be easier

I'd be suprised if mp3 really botched a single sine

but even if that's true you can still play .wav/flac on some players, even more if you include those you can RockBox

if you need a little more V then Radio Shack has audio isolation xfmr that can be wired for 2x (auto xmfr mode)

Last edited by jcx; 17th November 2011 at 01:10 AM.
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Old 18th November 2011, 05:05 PM   #9
graygem is offline graygem  United States
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Quote:
Originally Posted by jcx View Post
I'd be suprised if mp3 really botched a single sine
I didn't really believe it myself until I tried it.

But that is beside the point. I want to build a stand alone 1KHz sine wave generator powered from 3V
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Old 18th November 2011, 06:09 PM   #10
jcx is offline jcx  United States
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I don't see big problems -80 dB spurs are pretty good compared to what a "simple" analog sine oscillator will do

no way you're going to get the narrow linewidth even a poor xtal in a cheap DAP will give



I created a 1 kHz sine in Ltspice - exported with the .wave function

used foobar2000, lame 3.99.2, encoded as mp3 v2,

reconconverted to .wav - back in to Ltspice

below is a 1048576 point fft of 10 seconds 1kHz sine > 16/44.1 .wav > mp3 v2 > .wav
Attached Images
File Type: png mp3_sine.PNG (50.7 KB, 147 views)

Last edited by jcx; 18th November 2011 at 06:15 PM.
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