Hi Neil,

I'm sorry, but I'll have to download something to open the .tgz file (Linux
compression format?)

Don't worry about the code -- I know the feeling -- either you never have
the time to do it the way you want, or you just realized how much you've
grown as a coder when you look at old code and say "did I write that"?

Thanks very much.

Regards,

Ken Pergola



-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Picdude
Sent: Sunday, August 10, 2003 1:47 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE]: 1% resistors - How to find exact integer multiples of
each other


Attached.  If you can't open .tgz, I can send a zip instead.

There were supposed to be 2 data files of resistance values (with 1 per
line)
-- the intention was that the primary is the resistors I actually have, and
the secondary is what I can get.  But IIRC, I never finished implementing
the
secondary-resistors file.

The tolerance you specify is the tolerance to the stated value, and does not
take the resistors' tolerances into account.

Excuse the coding inefficiency -- it had been a while since I programmed
anything serious in C. :-)

I'm actually looking at the code now, so give me a couple minutes and I'll
see
if I can convert it easily.

Cheers,
-Neil.



On Sunday 10 August 2003 00:08, Ken Pergola scribbled:
> Hi Neil,
>
> Thanks. If you don't mind sending it I'd appreciate it greatly. Right now
> I'm just playing with this in Excel.
>
> Thanks kindly,
>
> Ken Pergola
>
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Picdude
> Sent: Sunday, August 10, 2003 1:06 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: 1% resistors - How to find exact integer multiples of
> each other
>
>
> I wrote a C program some months ago that asks for a resulting resistance,
> then it chooses 2 resistors from a list of standard values and calculates
> how
> it could come up with the resulting resistance either in parallel or
> series. It outputs many possible combinations within a tolerance that you
> also enter.
> And it sorts in by how close it gets.
>
> With a few minutes of work, you could adapt it for voltage dividers quite
> easily.  Let me know if you want it, and I'll forward it.
>
> Cheers,
> -Neil.
>
> On Saturday 09 August 2003 21:47, Ken Pergola scribbled:
> > Sorry guys -- I made a mistake in the text -- I meant 12.0 K ohms for
the
> > upper leg instead of 6.0 K ohms. Sorry for the confusion and brain
lapse.
> > Corrected text below.
> >
> > Regards,
> >
> > Ken Pergola
> >
> >
> >
> >
> >
> >
> >
> >
> > Hi,
> >
> > Kind of a strange question but very basic:
> >
> > Without pulling out the calculator or spreadsheet and doing it manually,
> > what is the quickest way to come up with resistors that are exact
>
> *integer*
>
> > multiples of each other (from the 1% standard value list)?
> >
> > Let me elaborate: In other words, say I want to make a 'divide by 4'
> > voltage divider using 1% resistors and *only* two resistors (no building
>
> of
>
> > new resistance values allowed).
> >
> > For example, let me pick 2.00 K ohms as the bottom leg of the voltage
> > divider.  That means I need 12.00 K ohms as the upper leg of the voltage
> > divider. Well, 12.00 K ohms is not a standard value, so I need to try
> > again: So I'll try the next standard value for the bottom leg -- 2.05 K
> > ohms (standard value). This would require 12.3 K ohms as the top
resistor
> > which is not a standard value. Try again...ad nauseam...
> >
> > Some values are exact integer multiples of each other -- what's the
> > quickest and easiest way to identify them?
> > Does anyone have something in their 'toolbox' they'd like to share?
> >
> > Does anyone know of any existing chart, software, or Excel spreadsheet
>
> that
>
> > already exists to do this. I realize this is simple math and I could go
>
> off
>
> > and do this myself, but it would be nice having something that already
> > exists. I'm sure a lot of people have had a need for this at one time or
> > another.
> >
> > Thanks very much.
> >
> > Best regards,
> >
> > Ken Pergola

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