this is exactly the type of info that is not in any book. thanks for this.
@Olin, your every point is well valid and taken. very true why should i be
telling you. I just got a bit unreasonable there. Sorry to annoy.



On Sun, Oct 18, 2009 at 8:52 PM, Jinx <joecolquitt@clear.net.nz> wrote:

> > if you have any specific suggestions please do let me know.
>
> ___ ___, which PIC are you using ? The answers to your questions
> will be roughly the same for most PICs but code examples will not
>
> > i also need to know whether this sort of an app will require the use of
> > interrupt on rising edge feature only or timers as well?
>
> Some PICs do not have interrupts. A timer will not be of any use to
> you to track an input with an output LED
>
> > 2. how is the ADC result is used when its finally converted? i mean,
> > how to use the 10 bit result to do something? some code explanation
> > will do
>
> An analogue reading is used to determine the state of an analogue
> condition. Such as the position of a potentiometer, the output of a sensor
> for temperature, pressure, light etc, the voltage on a battery. There are
> countless real world applications
>
> Consider something like measuring a car battery. Keeping it simple, the
> PIC can have 5V on an analogue input. With 0V on this input, the ADC
> result will be 0. With 5V on the input the ADC result will be 1023, which
> is a range of 10 bits or 2^10. 12V (nominally - it could be as high as 15V)
> from a car battery is too much for the input, so you might use a couple of
> resistors to attenuate the battery voltage to a maximum of 5V at the PIC
> input. For argument's sake, divide by 3
>
> If the battery voltage happens to be 12.76V, due to the attenuation of
> the resistors, what will appear at the PIC pin is 12.76 / 3 = 4.25V
>
> As seen above, the expected ADC result is (4.25 / 5) * 1023 = 869.
> In other words, 1023 represents 15V, therefore 869 represents 12.76V
>
> Working the other way, if the ADC result is 907, then the battery voltage
> that represents is (907 / 1023) * 15 = 13.30V
>
> In a real world automotive application, the voltage range of interest would
> likely be between 11V and 14V, so the PIC and associated components
> would be configured to provide an output representing a 3V span over
> the range of the ADC
>
> wbr
>
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