by Eeyore <rabbitsfriendsandrelations@[EMAIL PROTECTED]
>
Apr 23, 2008 at 11:26 PM
"J.Koning" wrote:
> "Eeyore" <rabbitsfriendsandrelations@[EMAIL PROTECTED]
> wrote
> > Iain Churches wrote:
> > > "J.Koning" <mynamespacedbydots@[EMAIL PROTECTED]
> wrote
> > > > "Iain Churches" <IainNG@[EMAIL PROTECTED]
> wrote
> > > >
> > > >> > I suspect the simplest way to go is just to ramp the heater
> > > >> > voltage rather than limit the current actually.
> > > >> > It'll be simpler to make and have a lower overhead.
> > > >>
> > > >> How should this be done?
> > > >>
> > > >> Iain
> > > >
> > > > [...]
> > > >
> > > > See: "slow turn on regulator", page 15.
> > > > http://www.national.com/ds/LM/LM117.pdf#page=1
> > > > For better availability use the LM317 equivalent.
> > > >
> > > > [...]
> > > > to unsnip see my yesterday post.
> > >
> > > Thanks Jan. I had not realised that Graham was
> > > referring to the same ideas for which you had
> > > already posted the links:-)
> >
> > It strikes me as the simplest and most practical solution. R2 would
want
> > to be 1.1k using the schematic shown.
>
>
> With fresh batteries in my brain prosthesis
> for R2=1k1 (& R1=240) I find Vo to be about 7V.
Ah yes, I know what I did now, I 'lost' 100 ohms somewhere ( I typed in
1240/240 instead of 1340/240)
> Another set of fresh batteries shows R2 would
> want to be 970 ohm using the schematic shown.
You are quite correct. R1 and R2 should be 1% types of course.
Oh and forget the 2N2905 and substitute whatever small-signal pnp device
you
fancy like BC558.
Graham
