Technical Specification Introduction The SRF05 is an evolutionary step from the SRF04, and has been designed to increase flexibility, increase range, and to reduce costs still further. Range is increased from 3 meters to 4 meters. A new operating mode tying the mode pin to ground allows the SRF05 to use a single pin for both trigger and echo, thereby saving valuable pins on your controller. The SRF05 includes a small delay before the echo pulse to give slower controllers such as the Basic Stamp and Picaxe time to execute their pulse in commands. To use this mode, just leave the mode pin unconnected - the SRF05 has an internal pull up resistor on this pin. Mode 2 - Single pin for both Trigger and Echo This mode uses a single pin for both Trigger and Echo signals, and is designed to save valuable pins on embedded controllers.
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The ultrasonic sound is pulsed at 40 kHz and is not audible to the human ear. These modules are commonly used on robotic vehicles for obstacle detection and avoidance. Because they use sound waves for detection they are not sensitive to light sources or optically reflective surfaces like IR can be.
The fact that the sensors look like a couple of eyes adds to the cool factor as well. This will cause the module to start a detection cycle.
If an echo is not returned no object detected , the module will still lower the ECHO pin after a fixed delay. This delay may vary, but is about mSec on the modules that I have measured. This is required to prevent the module from hanging if there is no return echo.
If you run the test software shown down below and then block the sensor with your hand , you will see what is returned when no obstacle is detected. This is typically something along the lines of feet. To be safe, it is generally best to assume that any reading over about 15 feet is the same as no obstacle being detected.
Module Connections: There is a 5-pin header on the assembly. The OUT pin is not used. This pin is held high for the duration of the the measurement cycle. This ground needs to be in common with the uC. These are much more capable than the basic IR obstacle avoidance sensors that come in sensor kits and are highly recommended if you are building a motorized robotic car and want to implement a nicely capable obstacle avoidance system or just want to measure distance for some other reason.
The module has a built-in small microprocessor which does all the heavy lifting of managing the ultrasonic sensors.
A similar sensor module that takes care of the of echo timing and temperature measurement for you is the US as shown down below. Since the speed of sound varies with the temperature, for maximum accuracy the temperature can be measured and used in the calculation, so this is broken out in the code below but defaults to 20C.
It would be straight forward for instance to implement a DS18B20 or LM35 temperature sensor so that the actual temperature can be measured and used in the calculation. There is also a plastic holder available to mount the module as shown below.
Notes: Active circuitry is on the back of the module, so care should be used to avoid possible electrical shorts. Technical Specifications.
HY-SRF05 Ultrasonic Range Finder Module
Ultrasonic Sensor - HY-SRF05