Decimal to Degrees mathematics help

[RFsolution]

Hi All,

I'm working on some code to read a AC or DC motors position
using a potmeter as indicator having max 5V at the whiper

I'm using the 16F819 with 10bit AD

I was wondering how I can convert the AD word value to 360 deg, as PBP has
limited math possibilitys

In the final code I want to implement a setup routine so that I can determine
which Digtal value (word) corresponds to 360deg or max azimuth to do the final divide

Can someone help me with the mathematics part as I dont see how to do that

Lets say that we have the following variables:

AZdeg position 0 to 360 deg
AZdig position from AD convertion
AZdigmax value which corresponds to 360deg (during setup) so here we have to determine the divide ratio

Thanks all for your time reading my request

[sayzer]

If what I understood is correct, then a simple experiment could be as follows.

At 0 degree, record ADC value. Say it shows 150 (this would be your base value).

At 360 degree, record ADC value. Say it shows 900.

Then each degree would become as;
(900-150) / 360 = 2.

That means, when your ADC reading is 152, you will know that you are at 1st degree, 154 is 2nd, 156 is 3rd. etc...

With an additional math, which I am sure you can figure out, you can get the exact degree.


Was this what you needed, or I am in a different page?



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[Acetronics2]

At 0 degree, record ADC value. Say it shows 150 (this would be your base value).

At 360 degree, record ADC value. Say it shows 900.

Then each degree would become as;
(900-150) / 360 = 2.

That means, when your ADC reading is 152, you will know that you are at 1st degree, 154 is 2nd, 156 is 3rd. etc...

With an additional math, which I am sure you can figure out, you can get the exact degree.


Was this what you needed, or I am in a different page?



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Hi, Sayzer

... life is easy with you !!!

RF:

at first, be sure to use the posssible max of the ADC range for your measure ...

As said by sayzer, read the min ( 0°) and Max ( 359.9 °)

then you get a result between 0 and 1023 ... no use to look at a better than .1% precision ( humour )

But, to keep decimals, just multiply the result by ... 64 , to use the max counting possibilities of the Pic.

so, let's make it clear:

Scale = MaxValue - MinValue

dummy = ( AdcResult - MinValue ) x 64

' disable interrupts ... if necessary

dummy = dummy x 360

Result_64 = DIV32 Scale

' re enable

Now, dividing Result_64 by ... 64 ( 6 right shifts ...) give the INT part.

... and , if needed, the 6 right digits will give 64 x the decimal part.... a little bits shifting ( or multiplying i.e. by 100 )and you can show it !!!


life is sooooooooo simple ....

Alain

[sayzer]

Be My teacher Alain!


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[Ingvar]

Keep in mind that "normal" potentiometers are NOT very linear. There are special types for positioning purposes.

[sayzer]

Keep in mind that "normal" potentiometers are NOT very linear. There are special types for positioning purposes.

Multi turn pots could be a good choice for positioning.
In 360 degree, with the help of some gears, the pot can turn 10 times.

Thus, Alain's math can have a better accuracy.