Calculating Percent question

Using Arduino Programming Questions
1

Hey everyone,
I was adding a servo to display fuel level (volts really) in my sons arduino two wheel robot,
I tried using this formula ' (100/22)cell,
If cell = 22 value then the answer should be 100, or full,
However the arduino gives me 88!!! every time.
It gives 0 for 0, correctly,
So to solve this I had to use ' cell4.54 , which gives me the 0 at 0 and 100(full) at 23.

Why does the arduino do this?, I noticed in some other sample code that the programmer used the * figure also.
My calculator does it fine.
Regards, Matt.

2

That's probably because it uses an integer division by default. The fraction part is just cut off.

To use floating point numbers, try (100.0/22) instead.

Pieter

3

Or, change it to: (cell * 100) / 22

In integer math, 100 / 22 = 4, and 4 * 22 = 88.

Using the equation above, 22 * 100 = 2200, and 2200 / 22 = 100

Regards,
Ray L.

4

Oh crap I even read about that a while ago in the help, I forgot about integer math , Thanks for the reply guys.