S'2 WEEK 4 => 4 FEB - 10 FEB

The HRLV-MaxSonar-EZ sensor line is the most cost-effective solution for applications where precision range-finding, low-voltage operation, space saving and low-cost are needed. This sensor component module allows users of other more costly precision rangefinders to lower the cost of their systems without sacrificing performance.

Additionally, this sensor line allows cost-sensitive designers to choose this precision sensor as a performance upgrade over other lower performance sensors.

The HRLV-MaxSonar-EZ sensor line provides high accuracy and high resolution ultrasonic proximity detection and ranging in air, in a package less than one cubic inch. This sensor line features 1-mm resolution, target-size and operating-voltage compensation for improved accuracy, superior rejection of outside noise sources, internal speed of-sound temperature compensation and optional external speed-of-sound temperature compensation. This ultrasonic sensor detects objects from 1-mm to 5-meters, senses range to objects from 30-cm to 5-meters, with large objects closer than 30-cm typically reported as 30-cm. The interface output formats are pulse width, analog voltage, and serial digital in either RS232 or TTL. Factory calibration is standard.

Precision Ultrasonic Range Sensing

• Range-finding at a fraction of the cost of other precision rangefinders.

• Reading-to-reading stability of 1-mm at 1-meter is typical.

• Accuracy is factory-matched at 1-meter to 0.1% providing a typical large target accuracy of 1% or better for most voltages.

• Calibrated acoustic detection zones allows users to choose the part number with the detection zone that, matches their specific application.

• Compensation provided for target size variation and operating voltage range.

• Internal temperature compensation is standard.

• Optional external temperature compensation.

Very Low Power Requirements

• Wide, low supply voltage requirements eases battery powered design.

• Low current draw reduces current drain for battery operation.

• Fast first reading after power-up eases battery requirements.

Easy to use Component Module

• Stable and reliable range readings and excellent noise rejection make the sensor easy to use for most users.

• Easy to use interface with distance provided in a variety of outputs.

• Target size compensation provides greater consistency and accuracy when switching targets.

• Sensor automatically handles acoustic noise.

• Sensor ignores other acoustic noise sources.

• Small and easy to mount.

• Calibrated sensor eliminates most sensor to sensor variations.

• Very low power ranger, excellent for multiple sensor or battery based systems.

Range Outputs

• Pulse width, (1uS/mm).

• Analog Voltage, (5mm resolution).

• Serial, (RS232 or TTL, where TTL format by solderable jumper or volume orders available as no-cost factory installed jumper).

General Characteristics

• Low cost ultrasonic rangefinder.

• Sensor dead zone virtually gone.

• Size less than 1 cubic inch with easy mounting.

• Object proximity detection from 1-mm to 5-meters.

• Resolution of 1-mm.

• Distance sensor from 30-cm to 5-meters.

• Excellent To Mean Time Between Failure (MTBF).

• Triggered operation yields a real-time.

• 100mS measurement cycle.

• Free run operation uses a 2Hz filter, with 100mS measurement and output cycle.

• Operating temperature range from -15°C to +65°C, provided proper frost prevention is employed.

• Operating voltage from 2.5V to 5.5V.

• Nominal current draw of 2.5mA at 3.3V, and 3.1mA at 5V.

Applications & Uses

• Bin level measurement.

• Proximity zone detection.

• People detection.

• Robots ranging sensor.

• Autonomous navigation Distance measuring.

• Long range object detection.

• Environments with acoustic and electrical noise.

• Height monitors.

• Auto sizing.

HRLV-MaxSonar®-EZ™ Pin Out

Pin 1- Temperature Sensor Connection: Leave this pin unconnected if an external temperature sensor is not used.

Pin 2- Pulse Width Output: This pin outputs a pulse width representation of the distance with a scale factor of 1uS per mm. Output range is 300uS for 300-mm to 5000uS for 5000-mm. Pulse width output is up to 0.5% less accurate than the serial output.

Pin 3- Analog Voltage Output: On power-up, the voltage on this pin is set to 0V, after which, the voltage on this pin has the voltage corresponding to the latest measured distance. This pin outputs an analog voltage scaled representation of the distance with a scale factor of (Vcc/5120) per 1-mm. The distance is output with a 5-mm resolution. (This output voltage is referenced to GND, Pin 7.) The analog voltage output is typically within ±10-mm of the serial output.

Using a 10bit analog to digital convertor, one can read the analog voltage bits (i.e. 0 to 1024) directly and just multiply the number of bits in the value by 5 to yield the range in mm. For example, 60 bits corresponds to 300-mm (where 60 * 5 = 300), and 1000 bits corresponds to 5000-mm (where 1000 * 5 = 5000-mm).

A 5V power supply yields~0.977 mV per 1 mm. Output voltage range when powered with 5V is 293mV for 300-mm, and 4.885V for 5000-mm.

Pin 4- Ranging Start/Stop: This pin is internally pulled high. If this pin is left unconnected or held high, the sensor will continually measure and output the range data. If held low, the HRLV-MaxSonar-EZ will stop ranging. Bring high for 20uS or longer to command a range reading.

Real-time Range Data: When pin 4 is low and then brought high, the sensor will operate in real time and the first reading output will be the range measured from this first commanded range reading. When the sensor tracks that the RX pin is low after each range reading, and then the RX pin is brought high, unfiltered real time range information can be obtained as quickly as every 100mS.

Filtered Range Data: When pin 4 is left high, the sensor will continue to range every 100mS, but the output will pass through a 2Hz filter, where the sensor will output the range based on recent range information.

Pin 5-Serial Output: By default, the serial output is RS232 format (0 to Vcc) with a 1-mm resolution. If TTL output is desired, solder the TTL jumper pads on the back side of the PCB as shown in the photo below.

For volume orders, the TTL option is available as no-cost factory installed jumper. The serial output is the most accurate of the range outputs. Serial data sent is 9600 baud, with 8 data bits, no parity, and one stop bit. V+ Pin 6 - Positive Power, Vcc: The sensor operates on voltages from 2.5V - 5.5V DC. For best operation, the sensor requires that the DC power be free from electrical noise. (For installations with bad electrical power, a 100uF capacitor placed at the sensor pins between V+ and GND will typically correct the electrical noise.)

GND Pin 7: Sensor ground pin: DC return, and circuit common ground.

Dead Zone

Ultrasonic sensors have a dead zone in which they cannot accurately detect the target. This is the distance between the sensing face and the minimum sensing range. If the target is too close, the tone bursts leading edge can travel to the target and strike it before the trailing edge has left the transducer. Echo information returning to the sensor is ignored, because the transducer is still transmitting and not yet receiving. The echo generated could also reflect off the face of the sensor and again travel out to the target. These multiple echoes can cause errors when the target is in the dead zone.

  

Beam Angle

The beam cone angle values are the 3 dB points (i.e., points at which the sensor signal is attenuated by at least 3 dB). Outside this cone angle, the ultrasonic signal exists, but is rather weak. Targets may still be detected. This can be experimentally determined.

Beam Cone Diameter

The ultrasonic sensor emits ultrasound wave in a beam angle cone that eliminates side lobes. Target size versus beam spot size is important. Theoretically, the smallest detectable target is one half the wavelength of the ultrasonic signal.

Ultrasonic transducer is embedded, watertight, into the sensor housing, in polyurethane foam. The transducer transmits a packet of sonic pulses and converts the echo pulse into voltage. The integrated controller computes the distance from the echo time and the velocity of sound. The transmitted pulse duration and the decay time of the sonic transducer result in a blind zone in which the ultrasonic sensor cannot detect an object. Normally, the ultrasonic frequencies are between 65 kHz and 400 kHz, depending on the sensor type and the pulse repetition frequency is between 14 and 140 Hz.

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