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Thread: Electronics Help Needed

  1. #1
    Rob
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    Electronics Help Needed

    Bascially I need a 550k clock for an ADC, now it's not really possible to go this high with a 555, I've tried and they keep falling over, about 100k is really there limit.

    Now I know it's more than possible to knock up a simple astable multivibrator using a couple of inverters and a cap & to resistors, which will easilly provide the clock frequency I want.

    What I don't know is the formula to calculate the capacitor & resistor values, based on the desired frequence?

    Is it a case of T = 1/RC or similar?

    I'll try and post a scematic of what I'm on about.

    Any help would be great, if not it looks like it'll be a case of trial and error.

    Rob
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  2. #2
    Rob
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    Worked it out

    Here's the circuit:



    And here's the formula:

    F = 1 / ( C * ( R1 + R2 ))

    Worked it out via trial and error.
    And you say people actually pay money for M$ Windows?
    www.mp3mini.co.uk (Does what it says on the URL) www.openclassic.co.uk (The new car, with zero rust!) www.rob-web.co.uk (My other site)
    Total re-design underway: on the whole progress is very slow as the car is taking up too much time :)

  3. #3
    FLAC
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    Re: Worked it out

    Originally posted by Rob
    Here's the circuit:



    And here's the formula:

    F = 1 / ( C * ( R1 + R2 ))

    Worked it out via trial and error.
    If you use a Schmitt trigger input you can do it with one R and one C and f = 1/RC
    MPEGBOX - Plexiglass Computer
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