mesamune80

Hi All,

Anyone of you all come across this device?

http://www.optekinc.com/pdf/opb702.pdf

And anyone can provide the simple connection diagram for this device?

Thanks.

dknguyen

The datsheet gives you the internal schematic- a photodiode with a photodetector. Wire up the photodiode with a current limiting resistor the same way you would wire up an LED, and simply wire up the photodetector as an open collector (with a pull-up resistor if you want to measure analog rather than digital).

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mesamune80

thanks for the information given,but if i would like to give on /off signal to my pic micro controller which i need 5v for high logic how could i achieve that?
Thanks.

dknguyen

You have the photo-diode pull the pin to ground whenver it triggers and have a pull-up resistor bring the pin high the rest of the time (like I described previously).

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mesamune80

i just tried to connect pin 1 via a 1k resistor then to 12v pin 2 to GND ,
and pin 4 to 12V and pin 3 to my microcontroller and i got the reading just 0.92v?

dknguyen

Pin 3 should go to ground, while pin 4 should to your uC pin AND go to 5V through a resistor (to pull the pin high when the transistor is not on and not pulling the pin low).

Also, your 1K resistor is too small and would burn out the LED. THe datasheet says it has a 1.7V drop for 20mA if it is a IR LED and a 2.4V drop at 40mA if it is a red LED (do you know which one your device has?)

You should size your resistor so that:
R = (Vsupply-Vdiode)/Inominal

(the extra voltage from the supply that isn't dropped across the diode must be dropped by the resistor, so if you use this extra voltage that is going to appear across your resistor in the equation in V=IR, you can figure out control how much current goes through the LED).

just like when sizing a resistor for a normal LED.

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mesamune80

ok,mine is IR LED so my R should be R=(5-1.7)/20mA=165ohms?

,i just tried to put 165ohm but when i block the photosensor the reading could not ground to 0V? Anything wrong ?

dknguyen

WHen the photo-detector has light on it, the transistor turns ON. THat means when there is light it pulls the pin to ground. WHen there is no light, the resistor pull the pin to 5V.

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mesamune80

can i power up pin 1 with a 510R resistor and pin3 with 4.7K pull up resistor?
as my Vdiode is 1.7v? is this correct??

mesamune80

But the above configuration power with different source one with (diode)12V and another one with 5 V (transistor).can i do it that way?