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  1. #1
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    What are timing capacitors and where are they used?

    What are timing capacitors?

    capacitors in parallel one side to ground is a storage capacitor
    capacitors in series is a frequency dependant

    But how are timing capacitors hooked up mostly? in parallel or in series?

    For Clocks circuits, 555 timers, oscillators, sample and hold have timing capacitors

    What other circuits use timing capacitors please? for TV's?,VCR's?,delay lines? Clocks? oscillators? radios?

    Can u please give me some examples of using a timing capacitor to set the "range" and "time duration" of the circuit please?

    Added after 5 minutes:

    Whats the difference between a timing capacitor VS a filter capacitor in a power supply they both store

    Does most timing capacitors have a comparator circuit to set the upper and lower threshold points so it adjusts the charging and discharging times?

    •   Alt23rd October 2006, 23:50

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  2. #2
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    Timing capacitors

    I've never seen in any kind of classifications timing capacitors, they not exist.
    Perhaps you are trying to say capacitor used to set time, or frequency.
    For example in the 555 there are una capacitor to set the frequency of operation.

    Tiimming capacitors are used un devices that need frequency to be adjusted. 555 is one of them, VCO's, PLL etc.

    In theory we use serial or parallel capacitorsin practice we mus have a lot of care.
    Example two capacitors in parallel gives you C1 + C2 = Ct. But each capacitor has a series resistor inside, called ESR, and are in parallel that gives you half resistance wich is very bad.
    On the other side Capacitors in series gives a total resitance of ESR1 + ESR2 that means a lot of losses.
    Manufacturers don't use serial o parallel capacitors.



    •   Alt24th October 2006, 02:21

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  3. #3
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    Re: Timing capacitors

    Filter capacitors= smoothing circuits its a diode rectified waveform
    (varying DC) and the capacitor smooths out the rectified waveform with its time constants store or hold time

    Timing circuits- a capacitor is to set the frequency,period,time duration,duty cycle

    there is some timing capacitors:
    http://home.cogeco.ca/~rpaisley4/LM555.html

    Each timing circuit has different duty cycle formulas,period formulas because of the added resistors

    The 555 timer chips has internal a comparitor and a threshold voltage and a discharge

    astable and monostable timing circuit has a capacitor that sets the time

    Controls the charge and discharge time of a capacitor:
    Trigger input: is 1/3 of Vs
    Threshold input: is 2/3 Vs
    discharge pin:
    Control input: to adjust the threshold voltage

    One resistor for charging time and 2 resistors for discharge time

    Is i have a RC network how can i build a network/circuit so control the charge and discharge timing?
    1.) i would need a discharge path
    2.) a Trigger input going to a comparitor#1 of 1/3 of 9 volts
    3.) a Threshold input going to a comparitor#2 of 2/3 of 9 volts

    Threshold comparitor- compares the control voltage pin on the 555 timer with the
    2/3 voltage of the threshold pin

    what is the difference between the trigger input pin Vs the threshold input pin they both have use comparitors in the 555 so whats the difference please?



    •   Alt24th October 2006, 08:00

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  4. #4
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    Re: Timing capacitors

    Trigger input: when < 1/3 Vs ('active low') this makes the output high (+Vs). It monitors the discharging of the timing capacitor in an astable circuit. It has a high input impedance > 2M.

    Threshold input: when > 2/3 Vs ('active high') this makes the output low (0V)*. It monitors the charging of the timing capacitor in astable and monostable circuits. It has a high input impedance > 10M.
    * providing the trigger input is > 1/3 Vs, otherwise the trigger input will override the threshold input and hold the output high (+Vs).
    Quoted from:
    http://www.kpsec.freeuk.com/555timer.htm
    where you can find detailed description of almost everything on the 555 timer ..

    Regards,
    IanP



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