Range Finding

The URM37 V3.2 Ultrasonic Sensor was the first thing that I connected to my Arduino.   It is a cool little piece of kit.   It is actually a sonar device in that it bounces ultrasonic beams off of things to measure their distance from the sensor by timing the echo. Note that the product to the right is NOT precisely the same device as I am using but does offer most of the same features. In any case, the one that I amusing can be connected either via PWM or serial (TTL or RS232) and if you use the serial interface you can also measure the temperature.   I just wanted simple range finding on command so I used the PWM input.   The user manual covers a lot more of the capabilities than I need!

As you can see from the picture it takes four wires to connect the sensor if you are using PWM.  Two power, the PWM output, and a trigger input.

Below is the Arduino code to read from the sensor.   This presumes you have already set the pins to output and input respectively and declared their variables!

    digitalWrite(triggerPin, LOW);
    digitalWrite(triggerPin, HIGH);
    range = pulseIn(inputPin, LOW);
    rangeCM = range / 50;

The only issue that I have had with this sensor has been one related to power.   If you don't give it good power it will limit the range of the sensor.   Drove me nuts.

Specification

• Power: +5V
• Current: <20mA
• Working temperature: -10 ~ +70 C
• Detecting range: 4cm-3m (3-5m is possible, but depending on situations)
• Resolution: 1cm
• Interface: PWM, RS232 or TTL (via Jumper)
• Servo control: One servo control output
• Operating Mode: Serial (PWM) passive control mode; Autonomous Mode; On/OFF Mode
• Temperature sensor: 12 bits reading from serial port
• Size: 22mm × 51 mm
• Weight: 30g