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Step 3Sensing the Visitors
No reason to make a phone call if no one is there to answer.
Using the PIR sensor is pretty simple. It is a simple device that trips a relay when there is a sufficiently large change in the ambient light around it. You'll have to read the documentation for the specifics, but in outline, you'll have your PIR's output attached to one pin of your microcontroller. The microcontroller will loop and check that pin for a change (becomes either high or low, depending on your PIR). When it detects motion, your microcontroller will start the phone to dialing...
Place the PIR somewhere at sufficient distance from the phone so that the phone can dial and ring before the visitor gets to the phone itself. If you time it carefully, it will ring about when they reach the desk.
On to dialing the phone.
Using the PIR sensor is pretty simple. It is a simple device that trips a relay when there is a sufficiently large change in the ambient light around it. You'll have to read the documentation for the specifics, but in outline, you'll have your PIR's output attached to one pin of your microcontroller. The microcontroller will loop and check that pin for a change (becomes either high or low, depending on your PIR). When it detects motion, your microcontroller will start the phone to dialing...
Place the PIR somewhere at sufficient distance from the phone so that the phone can dial and ring before the visitor gets to the phone itself. If you time it carefully, it will ring about when they reach the desk.
On to dialing the phone.
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