High Range IR Sensors.

[gauravkothari23]

Hi all,
I am working on a project, where i have to use Sharp GP2Y0A21YK0F Analog Distance Sensor 10-80cm.
what i need is... when any person crosses the IR sensor upto the distance of 70cm the LED connected to the output should get OFF till the person is in the front of the IR sensor. I am using LM393 comparator (circuit attached).
what my problem is.. the sensor detects the person only upto 45 to 50 cm.
what is the problem with the circuit. can anybody help me out.

 

[FvM]

what my problem is.. the sensor detects the person only upto 45 to 50 cm.

Sounds fair. 80 cm range is specified for objects for at least 90 % reflectance. Will be less with lower reflectance.

 

[gauravkothari23]

thanks..
yes. but as per the datasheet the voltage output at 80 cm is 0.40V, which is what i am getting. but how can i compare the same voltage using a comparator to let the LED get OFF at 70 CM.

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Sounds fair. 80 cm range is specified for objects for at least 90 % reflectance. Will be less with lower reflectance.

i have made a practical test to check if my sensor works perfect as per the datasheet. but yes this are the results i got..
if distance is greater than 80cm = V_Out = 0.20V
if distance is equal to 70cm = V_Out = 0.40V
if distance is equal to 60cm = V_Out = 0.50V
so how can i now compare the same voltage using a LM393 comparator, which i am not able to do. i have also attached my circuit diagram previously.

 

[FvM]

Maybe I misunderstand the question. According to your measurements a threshold of 0.4 V should work.