Hi.
Does anyone knows a simple schematic diagram for frequency-to-voltage conversion using simple components ?
Miguel
Frequency to voltage conversion...
Frequency to voltage conversion...
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Re: Frequency to voltage conversion...
I don´t have a scematic at hand, but you can try this:
A simple frequency-to-voltage converter is a one shot timer (555 family?) to ensure a constant pulse width, followed by an integrator (resistor in series and capacitor to ground).
Choose the pulse width so the max. frecuency you will convert has a longer period (1/frecuency).
Choose R and C so it´s time constant (RC) is larger than the period of the min. frecuency you will convert.
The output will depend on the ratio of the timer´s periods: Ton / TTotal.
But Ton is fixed and TTotal is 1/frecuency.
You may add a buffer so you don´t load the integrator.
A simple frequency-to-voltage converter is a one shot timer (555 family?) to ensure a constant pulse width, followed by an integrator (resistor in series and capacitor to ground).
Choose the pulse width so the max. frecuency you will convert has a longer period (1/frecuency).
Choose R and C so it´s time constant (RC) is larger than the period of the min. frecuency you will convert.
The output will depend on the ratio of the timer´s periods: Ton / TTotal.
But Ton is fixed and TTotal is 1/frecuency.
You may add a buffer so you don´t load the integrator.
E. Cerfoglio
Buenos Aires
Argentina
Buenos Aires
Argentina
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Re: Frequency to voltage conversion...
Exter
Google up LM2917 and check it out. Its a frequency to voltage converter. If you decide on this chip, beware of one thing--it requires an input with a duty cycle of 25% to %75%. They dont tell you this on the data sheet!
Google up LM2917 and check it out. Its a frequency to voltage converter. If you decide on this chip, beware of one thing--it requires an input with a duty cycle of 25% to %75%. They dont tell you this on the data sheet!
- Chris Smith
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Re: Frequency to voltage conversion...
9400
[RS 276-1790] if Rat Shack still carries them?
I have the schematics if you need them.
<small>[ October 28, 2005, 06:51 PM: Message edited by: Chris Smith ]</small>
[RS 276-1790] if Rat Shack still carries them?
I have the schematics if you need them.
<small>[ October 28, 2005, 06:51 PM: Message edited by: Chris Smith ]</small>
Re: Frequency to voltage conversion...
It depends on what you call "simple". A basic stamp can read very low frequency in period mode or higher using it's pulse in function. Output the result as a voltage with the pwm function.
YOu can make a charge pump with two diodes two capacitors and a resistor.
YOu can make a charge pump with two diodes two capacitors and a resistor.
Re: Frequency to voltage conversion...
Thanks, fellows.
The project is to have my cable driven old speedometer running from a modern transmission that outputs reluctor pulses.
The plan was/is reluctor F->V with a LM2917 and back to V->F with a NE566 to supply calibrable clock for a MC3479 stepper driver for the motor attached to the speedometer... convoluted, yes.
The NE566 and the MC3479 stepper driver and the stepper motor work. My LM2917 refuses to work; perhaps I alredy blew it.
The 9400 sounds as a good candidate, did not know it existed, thanks. Got the datasheet now.
Cannot get over ~500 rpm from the stepper motor. Perhaps it's not capable of much more.
Well, back to the bench.
Thanks !,
Miguel
The project is to have my cable driven old speedometer running from a modern transmission that outputs reluctor pulses.
The plan was/is reluctor F->V with a LM2917 and back to V->F with a NE566 to supply calibrable clock for a MC3479 stepper driver for the motor attached to the speedometer... convoluted, yes.
The NE566 and the MC3479 stepper driver and the stepper motor work. My LM2917 refuses to work; perhaps I alredy blew it.
The 9400 sounds as a good candidate, did not know it existed, thanks. Got the datasheet now.
Cannot get over ~500 rpm from the stepper motor. Perhaps it's not capable of much more.
Well, back to the bench.
Thanks !,
Miguel
- Abolish the deciBel ! -
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Re: Frequency to voltage conversion...
The nice thing about the LM2917 is that one was on the spindle motor controller board on the back of every 5.25" disk drive in existance -- or so it sometimes seemed. After harvesting the components from hundreds of those drives, you build up quite a stock! So, for a free F/V chip, find an old PC.
Dean
Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).
R.I.P.
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).
R.I.P.
Re: Frequency to voltage conversion...
You could use an XOR or XNOR gate. Feed the waveform direct to one input and via an RC network to the other. You get a fixed width pulse out every time the waveform changes polarity. Then integrate the pulses and measure their mean level.
Re: Frequency to voltage conversion...
YOU CAN FIND THE 9400 AND WORKING CIRCUITS IN THE BOOK BY FORREST MIMS PAGE 128 & 129 THE FORREST MIMS ENGINEER'S NOTEBOOK
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