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No need for analog.
Tie the cathode of the photo diode to the PIC pin with a 10M ohm pull up. The anode of the photo diode to zero(ground). When no light is detected the PIC pin will go LOW.
Used an IR diode for a dedicated light source.
You will have to shield from ambient light to keep from having false readings.
This is very similar to how a mouse works. Very fast and reliable.
I have used this setup to detect parts moving in excess of 6 inches per second.
Dave
Always wear safety glasses while programming.
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That means I just connect the IR LED continously to 5V with series resistor , no need to modulate the IR Tx?
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Correct.Originally Posted by Pic2008
As long as you do a little shielding for ambient light. Basically you can look at the modulation used in IR remote control applications as a way of electronically shielding.
Ty it. Take a photodiode, put a piece of heat shrink or something else around it so only the end can receive light. Connect it to a meter instead of the PIC, have sitting in a shadow. Hit the end of the photodiode with IR or some other light source and test.
You can also reverse the photodiode connection and have it detect light instead of dark.
Dave
Always wear safety glasses while programming.
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Word on the street is: Use a PIC with Schmitt trigger inputs for better results. Better results due to Schmitt triggers hysteresis's gives input port a snap action, dampens analog effect.
If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
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Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants - but debt is the money of slaves
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There simply is no "Happy Spam" If you do it you will disappear from this forum.
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Yesss Joe ...
Much better, as comparators directly can generate the interrupt ...
Over that I'd try to use a compensation stage to correct for ambiant light ... look at the attached scheme ... left side of Transistor T2.
Alain
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Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
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Along the same lines, the data sheet for the part Alain points out has on page 11 another nice way of doing it.
http://www.google.com/url?sa=t&sourc...SILdHEv5RRcHYQ
Dave
Always wear safety glasses while programming.
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Hi, Dave
Not so nice ...
as the goal, here, is to take care the detectors are not saturated by light ...
Alain
************************************************** ***********************
Why insist on using 32 Bits when you're not even able to deal with the first 8 ones ??? ehhhhhh ...
************************************************** ***********************
IF there is the word "Problem" in your question ...
certainly the answer is " RTFM " or " RTFDataSheet " !!!
*****************************************
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