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Science Forum Index » Electronics - Basics Forum » signal generator circuit
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| Guest |
 Posted: Mon Feb 05, 2007 2:05 am |
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I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
Thank you. |
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| Charles Schuler |
| Posted: Mon Feb 05, 2007 4:52 pm |
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Guest
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<bob@coolgroups.com> wrote in message
news:1170655527.560441.10450@s48g2000cws.googlegroups.com...
Quote: I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
A 555 timer IC is the easiest solution, but will provide a rectangular wave
of modest frequency stability (with the right timing components).
Tell us more:
1/ accuracy and stability
2/ waveform and allowable distortion if you need a sine wave output |
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| ian field |
| Posted: Mon Feb 05, 2007 6:09 pm |
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Guest
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"Charles Schuler" <charleschuler@comcast.net> wrote in message
news:H_SdnXnjBvFqBVrYnZ2dnUVZ_r2onZ2d@comcast.com...
Quote:
bob@coolgroups.com> wrote in message
news:1170655527.560441.10450@s48g2000cws.googlegroups.com...
I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
A 555 timer IC is the easiest solution, but will provide a rectangular
wave of modest frequency stability (with the right timing components).
Tell us more:
1/ accuracy and stability
2/ waveform and allowable distortion if you need a sine wave output
Not sure what the frequency spec is for the 555, I thought it tailed off
somewhere around 200kHz (according to the data sheet)
Many years ago I built the Manor supplies TV pattern generator which used
555s for both timebases - the 15.625kHz 555 couldn't be set reliably, the
frequency was all over the place - in the end I had to build a XCO TTL
timebase to replace the 555 circuits.
A great many "cheap gadgets" use 400kHz resonators well suited to an
unbuffered CMOS inverter oscillator, the output is sort of sinusoidal if a
bit low amplitude, but these days OP-AMPs that can handle those sort of
frequencies aren't as expensive as they used to be. |
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| Charles Schuler |
| Posted: Mon Feb 05, 2007 6:46 pm |
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Guest
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"ian field" <dai.ode@ntlworld.com> wrote in message
news:wWNxh.1496$Da4.438@newsfe6-gui.ntli.net...
Quote:
"Charles Schuler" <charleschuler@comcast.net> wrote in message
news:H_SdnXnjBvFqBVrYnZ2dnUVZ_r2onZ2d@comcast.com...
bob@coolgroups.com> wrote in message
news:1170655527.560441.10450@s48g2000cws.googlegroups.com...
I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
A 555 timer IC is the easiest solution, but will provide a rectangular
wave of modest frequency stability (with the right timing components).
Tell us more:
1/ accuracy and stability
2/ waveform and allowable distortion if you need a sine wave output
Not sure what the frequency spec is for the 555, I thought it tailed off
somewhere around 200kHz (according to the data sheet)
http://www.national.com/pf/LM/LMC555.html |
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| ian field |
| Posted: Mon Feb 05, 2007 6:52 pm |
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Guest
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"Charles Schuler" <charleschuler@comcast.net> wrote in message
news:YPednW5RQJFRLlrYnZ2dnUVZ_sudnZ2d@comcast.com...
Quote:
"ian field" <dai.ode@ntlworld.com> wrote in message
news:wWNxh.1496$Da4.438@newsfe6-gui.ntli.net...
"Charles Schuler" <charleschuler@comcast.net> wrote in message
news:H_SdnXnjBvFqBVrYnZ2dnUVZ_r2onZ2d@comcast.com...
bob@coolgroups.com> wrote in message
news:1170655527.560441.10450@s48g2000cws.googlegroups.com...
I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
A 555 timer IC is the easiest solution, but will provide a rectangular
wave of modest frequency stability (with the right timing components).
Tell us more:
1/ accuracy and stability
2/ waveform and allowable distortion if you need a sine wave output
Not sure what the frequency spec is for the 555, I thought it tailed off
somewhere around 200kHz (according to the data sheet)
http://www.national.com/pf/LM/LMC555.html
I was thinking of the pre-CMOS version.
<searches junk box for CMOS 555s> |
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| kell |
| Posted: Mon Feb 05, 2007 11:41 pm |
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Guest
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On Feb 5, 2:09 pm, "ian field" <dai....@ntlworld.com> wrote:
Quote: "Charles Schuler" <charleschu...@comcast.net> wrote in message
news:H_SdnXnjBvFqBVrYnZ2dnUVZ_r2onZ2d@comcast.com...
b...@coolgroups.com> wrote in message
news:1170655527.560441.10450@s48g2000cws.googlegroups.com...
I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
A 555 timer IC is the easiest solution, but will provide a rectangular
wave of modest frequency stability (with the right timing components).
Tell us more:
1/ accuracy and stability
2/ waveform and allowable distortion if you need a sine wave output
Not sure what the frequency spec is for the 555, I thought it tailed off
somewhere around 200kHz (according to the data sheet)
Many years ago I built the Manor supplies TV pattern generator which used
555s for both timebases - the 15.625kHz 555 couldn't be set reliably, the
frequency was all over the place - in the end I had to build a XCO TTL
timebase to replace the 555 circuits.
A great many "cheap gadgets" use 400kHz resonators well suited to an
unbuffered CMOS inverter oscillator, the output is sort of sinusoidal if a
bit low amplitude, but these days OP-AMPs that can handle those sort of
frequencies aren't as expensive as they used to be.- Hide quoted text -
- Show quoted text -
the multivibrator doesn't necessarily have to run at the signal
generator's intended output frequency. check this out:
http://www.electronic-circuits-diagrams.com/generatorsimages/1.gif
The discrete multivibrator on the left of the diagram obviously runs
at a fraction of the 455 kHz output frequency. Maybe the OP could use
a scheme like that? |
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| Phil Allison |
| Posted: Mon Feb 05, 2007 11:50 pm |
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"kell"
Quote:
the multivibrator doesn't necessarily have to run at the signal
generator's intended output frequency. Check this out:
http://www.electronic-circuits-diagrams.com/generatorsimages/1.gif
The discrete multivibrator on the left of the diagram obviously runs
at a fraction of the 455 kHz output frequency. Maybe the OP could use
a scheme like that?
** The 455kHz oscillator is on the right side of the schem, consisting of
the ceramic filter, T3 and the tank circuit.
The rest on the left is just an audio frequency modulator.
....... Phil |
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| kell |
| Posted: Mon Feb 05, 2007 11:54 pm |
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Guest
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On Feb 4, 10:05 pm, b...@coolgroups.com wrote:
Quote: I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
Thank you.
The resonant frequency of an LC tank circuit is f = 1/(2 Pi sqrt(LC)) |
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| Michael Black |
| Posted: Tue Feb 06, 2007 1:07 am |
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Guest
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(bob@coolgroups.com) writes:
Quote: I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
Thank you.
It would help if you'd specified what you wanted/needed this for.
The easiest, for someone wondering about inductors, would likely
be a crystal oscillator at some higher frequency, and then a divider
to get it down to the desired frequency. So a 4MHz crystal oscillator
and a decade counter would get you a nice 400KHz signal that only requires
wiring. Get one of those 4-pin ttl oscillators to take care of the
oscillator. You need to pick a frequency that will divide down to 400KHz,
unless of course you can live with some frequency close to that and then
you have a more open choice for the oscillator.
Someone mentioned ceramic resonators, and that would get you an exact
400KHz signal, though you might have to order the resonator. They are
right, you do see them in things, but I can't say how often I see them
so you might have to work through a lot of scrapped electronics before
you find one at 400KHz (though, again if you can live with something
a little different in frequency, you will have easier choices). You'll have
to wire up a crystal oscillator to use it.
Most common radios have a 455KHz (or more recently, 450KHz) intermediate
frequency, which means the IF transformers in them will likely be a good
start to an LC oscillator, though you'll need to add an oscillator, and
add some capacitance to tune the transformer down to 400KHz. And you have
to pull out the right one, since there will likely be 10.7Mhz IF
transformers in the same radios for the FM section.
If you don't need exactly 400KHz, you have more flexibility, since then
you don't have to worry about tuning it. If it just has to be somewhere
around there, the choices open up. If you need a sinewave, that will
change the solution.
Michael |
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| Rich Grise |
| Posted: Tue Feb 06, 2007 6:15 pm |
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Guest
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On Sun, 04 Feb 2007 22:05:27 -0800, bob wrote:
Quote: I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
Ach! Ignore those 555ists. ;-)
For what you're asking, since you've asked nicely, the frequency
is determined by
f = 1 / (2 * pi * (sqrt( R * C))
That's the resonant frequency. Their internal resistances, and
the added resistor, will affect the Q, or "quality factor" of
the circuit, which is related to how sharp of a resonance peak
you have.
Well, that's your tuned circuit - that's how you select a frequency.
But, to oscillate, (which is what you're trying to do) you need some
active element, to feed back the signal on itself, so that it will
maintain the oscillation.
Google things like "RC oscillator circuit" - what you find will
probably lead to further googling, and so on.
Good Luck!
Rich |
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| bugsbayani@gmail.com |
| Posted: Wed Feb 07, 2007 12:41 am |
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Guest
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On Feb 5, 2:05 pm, b...@coolgroups.com wrote:
Quote: I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
Thank you.
Why not make use of a Astable Multivibrator Circuit. Only two
transistors, two capacitors, and four resistors are needed. This
circuit produces a square wave. Regarding the frequency of 400 KHz,
the product of the base resistor and base capacitor should equal 1/400
ms (Time Constant).
Sincerely,
Bugs_Bayani |
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| kell |
| Posted: Wed Feb 07, 2007 10:37 am |
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Guest
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On Feb 6, 2:15 pm, Rich Grise <r...@example.net> wrote:
Quote: On Sun, 04 Feb 2007 22:05:27 -0800, bob wrote:
I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
Ach! Ignore those 555ists. ;-)
For what you're asking, since you've asked nicely, the frequency
is determined by
f = 1 / (2 * pi * (sqrt( R * C))
That's the resonant frequency.
Typo--
Delete R, insert L. |
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| Rich Grise |
| Posted: Thu Feb 08, 2007 3:32 pm |
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Guest
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On Wed, 07 Feb 2007 06:37:23 -0800, kell wrote:
Quote: On Feb 6, 2:15 pm, Rich Grise <r...@example.net> wrote:
On Sun, 04 Feb 2007 22:05:27 -0800, bob wrote:
I'd like to make a circuit that is essentially a signal generator
producing a 400 kHz signal. I think this can be done with a
voltage source, resistor, capacitor, and inductor in parallel.
However, I'm not sure what values are appropriate for the
resistor, capacitor, and inductor. Any help is appreciated.
Ach! Ignore those 555ists. ;-)
For what you're asking, since you've asked nicely, the frequency
is determined by
f = 1 / (2 * pi * (sqrt( R * C))
That's the resonant frequency.
Typo--
Delete R, insert L.
Yes. Thanks. :-)
Rich |
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