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Frequency multiplying

Discussion in 'Hobby Electronics' started by Sash, Apr 30, 2004.

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  1. Sash

    Sash Guest


    I'm wanting to build a circuit that receives a square wave input, and
    outputs it with a slightly different frequency, depending on a user
    adjustable value. I want to alter the frequency by about +/- 20% but it
    needs to be adjustable on the fly, ie. a trim pot or similar.

    Any ideas?
  2. Phil Allison

    Phil Allison Guest

    ** You will have to specify the range of frequencies involved AND the

    We need to know the application to get an idea of the performance
    requirements, power supply needs and decide if a simpler way than YOUR idea
    is possible and maybe preferable.

    ............ Phil
  3. A Frequency To Voltage Converter followed by a Voltage Controlled
    Might be as easy as using a trimpot and a few other bits to adjust the
    voltage from the FV converter which then goes into the VCO.
    Totally depends on your frequency requirements and application, but
    that's a good place to start.

    Dave :)
  4. Phil Allison

    Phil Allison Guest

    ** What if the OP wants to vary the 1.8 GHz clock on their PC by +/- 20 %

    With no details the question is just a mindless troll.

    ............ Phil
  5. Sash

    Sash Guest

    Sorry, should have included some background information.

    I want to input a square wave from the speed sensor in the gearbox of a car,
    and adjust this to calibrate the speedometer of the car. A different
    differencial has been fitted and it changes the gearing and the speedo. I'm
    not sure on the exact frequency's required but its as low as 10-15Hz
    (preferably lower) and up to about 450 Hz.

    Being in a car, it would run off 12V or less.

    Is there any other information that would help?
  6. Sash

    Sash Guest

    What sort of revices would I be looking at? Schematics?

  7. Bob M

    Bob M Guest

    Hi Sash

    I was faced with a similar challenge from a friend of mine. He changed
    the ratio of his final drive in his truck for better gas mileage and
    the speedo was off by 12% (reading low = speeding tickets). To build
    an analogue circuit that can work from 0 to 450 hz (yes the output is
    0 when you aren't moving) proved very difficult (extremely wide
    capture ratio).

    What I did instead was to calculate the exact change he made in the
    final drive and then modify the speedo circuit. It had a micro in it.
    All I did was replace the crystal with a new one that adjusted for the
    change (12% slower). It actually worked, much to my amazement. You
    might give this a try!

    Cheers from Canada

    Bob Morgoch
  8. Only in your little world Phil.

    I provided a potentially helpful reply without knowing the some
    details which the poster obviously forgot to include. No big deal to
    the rest of us, but obviously you have some sort of problem with it,
    as always...
    The post was as far from a "mindless troll" as I could imagine.

    Dave :)
  9. A Frequency-Voltage converter chip can be found here:,1850,2979,00.html
    Others are also available from other manufacturers.

    VCO's are a bit harder, but a Google search should bring up some info
    and schematics.

    Dave :)
  10. Phil Allison

    Phil Allison Guest

    "David L. Jones" <>

    ** I live in the real world - shame you have such a low opinion of it.

    Must be nice in that gilt edged ivory tower of yours - Dave.

    ** Get real you pathetic wanker !!!

    You took a wild guess at the facts instead of waiting for the OP to supply
    the relevant details.

    ** Stupidity is very common.

    ** You are obviously on very friendly terms with stupidity.

    ** That just shows what a pompous, posturing little fuckwit you really
    e - Dave.

    Same as ever.

    ............. Phil
  11. tony

    tony Guest

    Another option - is it possible to recalculate the speedo scale and
    print and attach a new one .... colour printers are quite good now

    Have fun!

  12. LMAO!

    Dave :)
  13. budgie

    budgie Guest

    (the usual snivelling crap)
    David, do what 80% of aus.electroincs have done - plonk! Phyllis is just a
    bitter old turd who abuses anybody who dares disagree with her.
  14. The disadvantage of using Google Groups - No PLONK!

    Dave :)
  15. Phil Allison

    Phil Allison Guest

    "David L. Jones" <

    ** Is there no end to this snivelling little prick's Jone's hypocrisy ???

    First he goes out of his way to personally abuse me for no good reason -
    then has the fucking hide to whinge he has trouble ignoring me because he
    choses to use Google Groups ????

    Jim Rowe told me 13 years ago Jones was a wanker.

    .............. Phil
  16. Whoa, now that was nasty!!
  17. LMAO!

    If I only had a dollar for every time I've heard the same and a lot
    worse about you Phil...
    I wouldn't think about KillFiling you Phil, you make me laugh.

    Dave :)
  18. Phil Allison

    Phil Allison Guest

    ** Which proves the fact.

    ** But you will not name them, none are not credible persons and they
    have never had any contact with me.

    ** Good - you can watch while I destroy you.

    ............... Phil
  19. Rod Speed

    Rod Speed Guest

    Just another of your pathetic little drug crazed fantasys, wanker.
  20. Phil Allison

    Phil Allison Guest

    "Rod Speed" <..

    ** So says a notorious usenet Zombie.

    No matter how many times he is shot full of holes he will not lie down.

    .............. Phil
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