James and Iliana Holbrook wrote:
>
> Hello,
>         As a beginner with PIC's I don't have the programming skills to
 implement
> a function that I would like to use. I have worked with the BASIC STAMP 2
> and would like to make a function that is available on the BS2. It's called
> the RCTIME command and what it does is read a resistive value by charging
> up a capacitor and measuring how long it takes to discharge through an
> unknown resistor.
>         My idea is to make a pin an output for a fixed length of time, change
 to
> input and loop until it went low, count the loops and return with the value.
>         Does this sound crazy ?? Would I be wasting my time trying to debug
 some
> code for this function ??
>         Any ideas would be appreciated. I'm using a 16C84 with a 4 mhz osc.
>         My goal is to read a photoresistor.
>         Thanks !!

Go for it - it works well. Here's a starting point :

              5V
              ---
               |
               |
               /
               \
               /   Light Dependant Resistor
               \
               /
     220 Ohm   |
----/\/\/\-----|
               |
               |
              ---
              ---  Cap
               |
               |
             -----
              ---
               -
You can use the formula : Time = LDR*Cap.
Don't leave out the current limiting resistor!


--
Friendly Regards

Tjaart van der Walt
mailto:tjaart@wasp.co.za
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