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The Sharp distance sensors are a popular choice for many projects that require accurate distance measurements. This IR sensor is more economical than sonar rangefinders, yet it provides much better performance than other IR alternatives. Interfacing to most microcontrollers is straightforward: the single analog output can be connected to an analog-to-digital converter for taking distance measurements, or the output can be connected to a comparator for threshold detection, making this an adjustable-threshold alternative to digital Sharp sensors. The detection range of this version is approximately 2 cm to 15 cm (0.8? to 6?).

The GP2Y0A51 uses a 1.5mm-pitch 3-pin JST ZH connector that works with our 3-pin JST ZH-style cable (not included), as shown below:

The wire color scheme matches the Sharp distance sensor pinout: red for power, black for ground, and white for signal.

It is also possible to solder three wires to the sensor where the connector pins are mounted, as shown in the picture to the right (you should probably add some hot glue for strain relief as a final step; this is not show in the picture because it would obscure the soldering). Because of the narrow pitch, it helps to have a fine-tipped soldering iron, and you should be very careful not to accidentally short two pins together with your wires or any added solder. When looking at the front of the sensor, the three connections are, from left to right, power (Vcc), ground, and the output signal (Vo).

Feature summary

• Operating voltage: 4.5 V to 5.5 V
• Average current consumption: 12 mA (note: this sensor draws current in large, short bursts, and the manufacturer recommends putting a 10 µF capacitor or larger across power and ground close to the sensor to stabilize the power supply line)
• Distance measuring range: 2 cm to 15 cm (0.8? to 6?)
• Output type: analog voltage
• Output voltage differential over distance range: 1.65 V (typical)
• Update period: 16.5 ± 4 ms
• Size: 27 mm × 13.2 mm × 14.2 mm (1.06? × 0.52? × 0.56?)
• Weight: 2.7 g (0.10 oz)

Linearizing the output

The relationship between the sensor’s output voltage and the inverse of the measured distance is approximately linear over the sensor’s usable range. The GP2Y0A51SK0F datasheet (312k pdf) contains a plot of analog output voltage as a function of the inverse of distance to a reflective object. You can use this plot to convert the sensor output voltage to an approximate distance by constructing a best-fit line that relates the inverse of the output voltage (V) to distance (cm).

Alternative Sharp distance sensors

We have a variety of Sharp distance sensors to choose from, including the short-range (4 – 30 cm) GP2Y0A41SK0F, medium-range (10 – 80 cm) GP2Y0A21YK0F, and long-range (20 – 150 cm) GP2Y0A02YK0F. These other analog distance sensors all have similar packages and identical pin-outs, making it easy to swap one version for another should your application requirements change. We also carry the newer Sharp GP2Y0A60SZ analog distance sensor (10 – 150 cm), which outperforms the other analog Sharp distance sensors in almost all respects, offering a low minimum detection distance, high maximum detection distance, wide 3 V output voltage differential, high 60 Hz sampling rate, operation down to 2.7 V, and optional enable control, all in a smaller package.

For short-range detection applications, we carry three digital Sharp distance sensors that have low minimum detection distances and a high 400 Hz update rate. They are available with a 5 cm, 10 cm, or 15 cm range and simply tell you if something is in their detection range, not how far away it is. They are smaller than the analog Sharp distance sensors and draw less current.

Note: The GP2Y0A51SK is different from our other Sharp analog distance sensors with JST PH connectors in two important ways: it uses a different 3-pin connector (JST ZH) that is not compatible with our JST PH cables or 0.1? connectors, and the mounting holes are in different locations, so it is not compatible with our brackets for Sharp distance sensors. Like with most of the other Sharp distance sensors we carry, the manufacturer recommends you insert a bypass capacitor of 10 µF or more between Vcc and GND near this sensor to stabilize the power supply line.

The GP2Y0A51SK0F model is a lead-free, RoHS-compliant version of the Sharp GP2Y0A51 Distance Sensor

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