RE: Re: Math & excel help required

["Ian Davidson" <ian@xxxxxxx>]

> You can do this in a spreadsheet, or write a little basic program to
> do this, but unfortunately, its unlikely to achieve what you need to
> do.  (Also, if you are writing in assembler, most assemblers can do
> repeat loops to build your table for you.)

A spreadsheet is what I needed so I could try a few different values
against my timer values.

> In order to make dimming appear to be equal stepped, you actually
> need to make the steps unequal.  Take a look at the graph at the
> bottom of this page: http://www.avolites.org.uk/products/special/fd-
> dimmer.htm which illustrates the relationship between percent
> apparent brilliance, and rms voltage you need to apply across a lamp.

Yep I know, that's why I need the spreadsheet to calculate the unequal
steps, Possible my explanation was a little unclear as I tried to
explain why I didn't want to just use the 100uS steps.

> To do a quickie linear spreadsheet, one need to know how many steps
> from zero to full brilliance, and what "thing" you want
output
> (which is usually a nuimber you feed into a timer, and you want this
> equally stepped), what the limit values are, and which direction to
> go in.

I want to vary the number of steps to see what effect it has on my timer
values, but likely 100.
The output I need is time i.e. step 1 = 14uS, step 2=16uS etc. Once I
have this I can calculate my timer values.

Hopefully that's a little clearer, If you have anything that will show
these calculations it would be useful and I could possibly convert it to
a spreadsheet. Once I'm happy with the values I will probably put them
into a lookup table to save time the program will be in its ISR so speed
is needed.

Ian D