[sdiy] Circon Controller questions (Moog's circuit)

[Mike Beauchamp]

Thanks for replying John,
The PDF I have for my 78xx's lists 1mv/C. I'm not sure if the "drift"
I am exeriencing is from temperature though. Looking at the LM317
datasheet, it also lists a "Long term stability" over 1000h which I
can't find an equivalent value for the 78xx's. Maybe this is the
statistic I should be looking at.

The input voltage dropping below 18V is also something I was worried
about (since I'm using half wave rectification), but I tacked on
almost 2000uF of capacitors on each input and I still get the same
result.. with my meter measuring ~20V of input. Thanks for the
suggestion though and I should be borrowing a scope from a friend this
week to see exactly what's going on in this regard.

I should probably move this thread to a more noob oriented message
board since it's just about power supplies and not specific synth
stuff.

Mike



On 5/29/07, John Luciani <jluciani at gmail.com> wrote:
> On 5/29/07, Mike Beauchamp <mikebeauchamp at gmail.com> wrote:
> > The problem I'm running into with the circon controller is exactly
> > that my +15 supply isn't as stable as I'd like it. It drifts slowly
> > over time, more than .6V over 20 hours. I'm starting to learn the hard
> > way why all the talented people on this list really are talented..
> > reference voltages, etc, etc. All things I've overlooked...
> >
> > In the meantime, i'm going to breadboard up a power supply using
> > LM317's and 337's over my 78xx and 79xx supply. If I can get a supply
> > that only drifts .3% (according to the LM317 datasheet), it will be an
> > exponential improvement over my 7815 drifting over 4%.
>
> What is the drift specification for the 78xx that you are using? I
> would be surprised
> if the drift is 4%. The datasheet that I have states a drift of 1.8mV/DegC. To
> get 600mV the Tj would be at 333 DegC and your requlator would be on fire!
>
> The maximum line regulation error is 150mV and the maximum load regulation
> error is also 150mV. All of these errors do not add up to 600mV. Have
> you measured
> the input and output voltage with an oscilloscope? Check to verify
> that your input
> voltage is not dropping below ~18V.
>
> (* jcl *)
>
>
> --
> http://www.luciani.org
>