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Sharp Infrared Distance Sensor

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This post covers my experiences with a Sharp IR sensor marked 2YOA2I F 7I  I received courtesy of @@bluehash clearing his desk a while back.


Sharp IR sensors can be obtained that cover ranges from 4 - 30 cm up to 100 - 550 cm.   This one has a listed range of 10 - 80 cm. The coverage envelope / angle was not listed in the data sheet but seemed relatively narrow. Current consumption is around 30 mA on average.   Response time is listed as 39 ms.  The output from the sensor is an analog voltage which is inversely proportional to the distance in a nonlinear manner.


Of particular note to those using TI microcontrollers is that it is a 5V device (the datasheet gives 4.5 to 5.5 V as the operating range for Vcc).  Most of my gizmos run off of 2 batteries at nominally 3V so I was interested in how it would work at lower voltages and ran a series of tests.  A bench power supply was used to supply constant voltage at 5.0, 4.5, 3.3, 3.0, and 2.5 Volts (accurate to better than 0.1 V).  I used a tape to measure the distance from the face of the sensor to a wall (distance accurate to 2 mm).  The voltage was measured with a digital multimeter and plotted against the inverse of distance to give a more linear curve.


Here are the results:


With Vcc set to 5.0 V and 4.5 V the output difference was minimal - the results are for all practical purposes the same and are in line with the datasheet.  The data for Vcc at 3.3 V and 3.0 V might be usable with the understanding that the curves began to offset some as Vcc drops, and that at 3.0 V the accuracy falls off at 15 cm, and at 3.3 V it falls off at 10 cm.  The sensor is not usable at 2.5 V.


If highest accuracy is required, a test like the one described here can be undertaken instead of just using the curve in the datasheet.

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