Decimal to Degrees mathematics help

[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.

[ErnieM]

Some things to keep in mind here (and elsewhere too):

1) The max number from the analog conversion is 1023, which is the maximum number expressible with the 10 bits from the converter. SO, the maximum resolution you can get is 360/1023= .3519 degrees per bit

2) Converting from raw A2D number to degrees is simple, just (assuming max reading is 1023, and min is zero) A2Dreading x 360 / 1023. However, it is important to perform the calculation by doing the multiplication first, then the division. If you divide first you’ll loose a lot of precision (do you see why?) You’re working with integer numbers here, so the decimal parts get lost quickly. Alain has a good point when he scale up the reading, just be careful you do not overflow the variable; his use of 64 is the most you can scale this number up

Max scale factor = biggest word / biggest expected number = 65535 / 1023 = 64.0165… so use 64. PBP does have some facilities for handling double precision multiplicands (32 bit products), but that’s trouble to deal with.

[sayzer]

Lets make it simple.

Try my way first.

You will be surprised with the result.

[RFsolution]

Hey Guys

very suprised about the fast reply's , thanks to all !!!

I will give it a try this evening.

I agree that potmeters are not that linair, and I dont need the 0.3 deg
precision, but 8bit is not enough

Will try sayzers solution this evening, if it is not working i will post the code
for the specialists

Thanks agn