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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 > > >