Ultrasonic sensors overcome many of the weaknesses of IR sensors - they provide distance measurement regardless of color and lighting of obstacles.

They also provide lower minimum distances and wider angles of detection to gaurantee that obstacles are not missed by a narrow sensor beam.

THIS particular model is an upgrade from the lower precision HC-SRO4. This has 5 pins and can be used in 1-pin trigger/echo or 2-pin.

Specifications

Check the datasheet for details and graphs but these are the highlights:

• Trigger Pin Format: 10 uS digital pulse
• Sound Frequency: 40 kHz
• Echo Pin Output: 0-Vcc
• Echo Pin Format: output is DIGITAL and directly proportional with range. See our conversion formula above.
• Measurement Range: 2cm to ~4.5m
• Measurement Resolution: 0.3cm
• Measurement Angle: up to 15 deg
• Measurement Rate: 40 Hz
• Supply Voltage: 4.5V to 5.5V
• Supply Current: 10 to 40mA
• Connector: standard 5-pin male connector which can plug directly into breadboards.

Measurement Procedure & Formula

Distance measurements can be made with microcontrollers in a straightforward manner:

You can find an Arduino Library with code here: http://forum.arduino.cc/index.php?topic=106043.0

• Send a 10 uS wide pulse to the sensor on the Trigger Pin. The sensor will automatically send out a 40 kHz wave.
• Begin monitoring the output from the Echo Pin and
• When the Echo Pin goes high, begin a timer.

• When the Echo Pin goes low, record the elapsed time from the timer and use the following conversion formula:

  Distance (in cm) = (elapsed time * sound velocity (340 m/s)) / 100 / 2

  Note: we divide distance by 2 because the sensor returns the round trip time, which doubles the distance measurement.