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Re: Terry's DRSSTC - Frequency/Pulse Width Controller

Original poster: "colin heath" <colin.heath4@xxxxxxxxxxxx>

hi malcolm,
                i have a feeling steve connor did this current source trick
with his oltc control also and had a much more linear result.
cheers
colin

----- Original Message -----
From: Tesla list <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, December 14, 2004 8:02 PM
Subject: Re: Terry's DRSSTC - Frequency/Pulse Width Controller


> Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>
>
> Hi Terry,
>
> On 13 Dec 2004, at 17:18, Tesla list wrote:
>
>  > Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
>  >
>  > Hi All,
>  >
>  > For my DRSSTC, I was going to have two knobs.  A 100k single turn pot
>  > in series with a 1k resistor to do the pulse width and basically act
>  > as a power controller following Steve's suggestion.  And another pot
>  > set up just like it (maybe a ten turn) for the pulse width.  The
>  > "linear" pulse width thing is easy with a LMC555 timer.
>  >
>  > However, most LMC555 circuits and their types are  "F : 1/R"  type
>  > circuits so the frequency control is not at all linear.  I was
>  > thinking zero on the pot would be like 1Hz, 25% on the pot 250Hz, 50%
>  > on the post 500Hz, 100% on the pot 1000 Hz...
>  >
>  > I just wanted to check to see if anyone and an easy simple way to do
>  > that?  I checked around for ICs and such, but did not find any
>  > wonderful solutions.  I can probably do it with a few simple digital
>  > chips, but thought I would ask...
>
> Use a current source in place of the timing resistor. Then cap
> voltage is a linear function of charge time.
>
> Malcolm
>
>
>