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Re: [Fwd: Spark gap not firing]
Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>
Tesla list wrote:
> Original poster: "Luc by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> Hi Terry, list,
> I'm in the process of designing a power supply and I try to find a formula to
> create a RC low pass filter (Terry NST filter protection ) I look at your
> on the web, I remember I read about it in the past but were ? I know if you
> change the value of R and C you change at what frequency the filter start
> to cut
> and how fast the db cut rise with the frequency. I could apply your value
> like to understand what I do . Can you help me to find the formula or if my
> memory is good the graph to calculated it ?
> Luc Benard
The expression for the half-power cutoff frequency of a low pass RC
filter is simply
Fc = 1/(2*pi*R*C)
where Fc is in Hz at which the output voltage/input voltage ratio is
0.707 [1/sqrt(2)] , R is in ohms, and C is in farads. This applies to
the simplified case of a filter between a zero-impedance source and an
infinite impedance load. In the case of such a filter inserted between a
TC primary circuit and a transformer, things may not be quite so simple.