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Attached is an image from the book I am going through. I don't quite understand the schematic and was hoping someone could explain it to me, including the use of the resistors. Like, does it matter where on the ground line the A0-A4 pins are connected? I have this all wired up and it's seems to be operating quite strangely.

IR Sensor Board Schematic

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  • \$\begingroup\$ When you say it's "operating quite strangely", what behavior do you expect, and what does it actually do? \$\endgroup\$ – The Photon Mar 12 '15 at 16:18
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It appears that each emitter is an IRLED and that they're all emitting all the time.

The detectors, on the other hand, work individually and each one only turns ON when it's hit with IR. Since their V1's are connected to +5V, when they're OFF no current will pass through them and the voltage across their 10k ohm pulldown resistors will be close to zero volts (GND).

On the other hand, when they're turned ON by IR, current will pass through them and the pulldown, with the result that a voltage will be developed across the pulldown which will be sent to the Arduino, letting the Arduino know that a sensor has picked up an IR signal.

The sensors appear to be used to detect IR reflected back from the emitter.

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  • \$\begingroup\$ I'd guess the detectors are reverse biased photodiodes. \$\endgroup\$ – George Herold Mar 12 '15 at 14:09

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