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555 timer question...

Discussion in 'Electronic Basics' started by Impmon, Jul 9, 2009.

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  1. Impmon

    Impmon Guest

    I wanted to build an astable timer with variable frequency, duty cycle don't
    matter. What I would like is to use variable resistor to obtain frequency
    of between 1 Hz and 100 Hz (not exact, just close)

    I've tried a few online calculator but with 3 variables, one being variable,
    makes computation tricky. The few I've tried doesn't really offer linear
    frequency change but rather ramps from low to high in just a touch of
    variable resistor knob. I have 100ohms, 10k, and 1 mega variable resistor,
    and assortment of fixed from 1 to 100 mega and several common value
    capacitors.

    TIA for any information that would help me.
     
  2. First the standard answer: Use a PIC :)

    Using a 555 you can achieve your frequency range in the standard a-stable
    configuration using a 0.47uF capacitor, a 470R resistor for R1 (often called
    Ra) and a 1M5 pot in series with a 15k resistor for R2 (Rb). However, the
    frequency will be highly nonlinear in relation to the turned angle of the
    pot.

    petrus bitbyter
     
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