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38khz Oscillator problem

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waldopulanco

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Hi Im here again! can i ask about 38khz crystal oscillator.
what CMOS can i use to oscillate the 38khz crystal and the output is 38khz and 19khz?

CMOS 4060 is complicated because there is no divide by 1! bacause i need is 38khz and 19khz with 38khz crystal. if i use 4020 there is no divide by 1 but have divide by 2 so the out is 19khz below no 38khz output and there is no oscillator.

is there any cmos that have an oscillator to oscillate the 38khz crystal and the output is 38khz and 19khz?

thanks!!
 

goldsmith

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Re: Need help about 38khz Oscillator

Hi Im here again! can i ask about 38khz crystal oscillator.
what CMOS can i use to oscillate the 38khz crystal and the output is 38khz and 19khz?

Hi
If you find a crystal which can work in 38 KHZ yes you can build it ( 38 KHZ or perhaps overtone harmonics )

If you want a pure 38 KHZ sine wave you have plenty of ways . for instance a bubba oscillator or perhaps wien bridge oscillator . or perhaps a Gated oscillator via not gates .

Best Wishes
Goldsmith
 

waldopulanco

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Re: Need help about 38khz Oscillator

i think it can be use to CMOS CD4060 with 38khz crystal! the output for 19khz is pin #7 how about the 38khz output can i use pin #9 or #10?

thanks!!
 

BradtheRad

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Re: Need help about 38khz Oscillator

When you want to divide a pulse train by 2, it is easy to use a single flip-flop.

There may also be a way to persuade a single flip-flop to oscillate with your 38kHz crystal.
 

waldopulanco

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Re: Need help about 38khz Oscillator

can you give me some sample circuit using flip-flop?
 

betwixt

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Re: Need help about 38khz Oscillator

And bear in mind that there are several outputs, each divided by 2 on a CD4060. You don't have to start with 38KHz, in fact there are many advantages to starting with a higher frequency, using the 4060's internal oscillator then using two 'adjacent' divided outputs for 38 and 19KHz. For example, you could start with a 1.216MHz oscillator and use the first pair of adjacent dividers at exactly 38KHz then 19KHz.

Brian.
 

waldopulanco

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Re: Need help about 38khz Oscillator

but i think there is no crystal with 1.216MHz value in my location!!
 

betwixt

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Re: Need help about 38khz Oscillator

Finding a 38KHz crystal as you originally suggested would be difficult too!

It can be a multiple of 1.216MHz (2.432MHz, 4.864MHz and so on) or you can use an RC network. A crystal is more stable and potentially more accurate but don't forget that by using a divider you would also divide any frequency errors. For example, if you used a commonly available 2.4576MHz crystal it would divide to 38.4KHz and 19.2KHz.

What is your application? Telling us will help find something suitable.

Brian.
 

BradtheRad

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Re: Need help about 38khz Oscillator

can you give me some sample circuit using flip-flop?

Schematic of 'D' (for 'data') flip-flop operating as a divide-by-two counter. The output has a 50% duty cycle no matter whether the input duty cycle is short (left diagram), or long (righthand diagram).

It is fine if you want to use a 4060.
The 4060, 4020, etc., perform a similar operation internally.

 

waldopulanco

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Re: Need help about 38khz Oscillator

I want to create a stereo encoder!! there are many stereo encoder on the internet but some limitation in my location! one their parts is not available in my location!! so i want to create that all parts is available in my location. the 38khz crystal will donate to me by my friend in the US.

i have no online payment like credit card to buy online all parts!!
 

Audioguru

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Re: Need help about 38khz Oscillator

I want to create a stereo encoder!! there are many stereo encoder on the internet but some limitation in my location! one their parts is not available in my location!!
If ordinary electronic parts are not available in your location then you cannot build many circuits.
Do gardening instead.
 

waldopulanco

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Re: Need help about 38khz Oscillator

If ordinary electronic parts are not available in your location then you cannot build many circuits.
Do gardening instead.

:grin: Lol!! Some component are available here are for tv, cd, radio, and other familiar appliances, but like a IC BA1404, NJM2035, 38khz, 76khz, 4860kHz crystal this not available here!!
 

Audioguru

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Re: Need help about 38khz Oscillator

The BA1404 is obsolete. It had poor performance and was replaced by much better FM stereo transmitter ICs many years ago. The replacement ICs are also obsolete.
 

betwixt

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Re: Need help about 38khz Oscillator

The second one will give slightly better audio but will be more expensive to build. You may not want the extra audio limiting stages though. It uses a 38KHz crystal.
The first is simpler and should work almost as well but needs a 4.864MHz crystal as I suggested before.

For an encoder, the 38KHz has to be fairly accurate (say +/- 200Hz). It doesn't matter at the encoding stage but many decoders have a limited 'lock-in' range.

Brian.
 

waldopulanco

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Re: Need help about 38khz Oscillator

The second one will give slightly better audio but will be more expensive to build. You may not want the extra audio limiting stages though. It uses a 38KHz crystal.
The first is simpler and should work almost as well but needs a 4.864MHz crystal as I suggested before.

For an encoder, the 38KHz has to be fairly accurate (say +/- 200Hz). It doesn't matter at the encoding stage but many decoders have a limited 'lock-in' range.

Brian.

the first 1 i was modified the schematic to make works to 38khz crystal using CD4069 and CD4013..
 

betwixt

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Re: Need help about 38khz Oscillator

What you have to be careful about is the purity of the 38KHz signal. Ideally it should be a perfect square wave, if the high and low periods are not equal you will find some signal from one channel goes to the other. This is why a higher frequency and divider is preferred, the action of dividing by 2 automatically makes it a square wave.

Brian.
 

waldopulanco

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Re: Need help about 38khz Oscillator

Here is my Schematic using Harry's 222 Stereo coder

Please let me know if i have mistake to the diagram, i hope you can help me to corredt it!!

Stereo_coder_38khz.JPG

thanks!!
 

betwixt

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Re: Need help about 38khz Oscillator

Looks OK to me.
The only potential problem is the signal at the output of U7A which is the square wave I mentioned earlier. In a simple oscillator like that you may find the high and low parts of the 38KHz are not equal width and therefore not switching the audio channels at the right time. It doesn't stop it working but the signal on one channel will leak into the other.

Please do not expect perfect results from this circuit, it is very basic. A 'pro' quality encoder would use a better channel switching circuit and would have filtering and phase adjustment on the pilot tone.

Brian.
 

waldopulanco

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Re: Need help about 38khz Oscillator

yes i know that this is basic encoder! can i put the input of U5A to the output of U7B? because it is on U7A. how do i add an adjustment to pilot tone or 19khz?

thank you so much!!
 

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