Part Number: SRF04
Function: Ultra-Sonic Ranger Finder
Package: Module type
The SRF04 was designed to be just as easy to use as the Polaroid sonar, requiring a short trigger pulse and providing an echo pulse. Your controller only has to time the length of this pulse to find the range.
The SRF-04 Timing diagram is shown below. You only need to supply a short 10uS pulse to the trigger input to start the ranging. The device will send out an 8 cycle burst of ultrasound at 40khz and raise its echo line high. It then listens for an echo, and as soon as it detects one it lowers the echo line again. The echo line is therefore a pulse whose width is proportional to the distance to the object. By timing the pulse it is possible to calculate the range in inches/centimeters or anything else. If nothing is detected then the SRF04 will lower its echo line anyway after about 36mS.
1. Voltage Current : 5V, 30mA Typ. 50mA Max
2. Frequency : 40KHz
3. Maximum Range : 3 m
4. Minimum Range : 3 cm
5. Sensitivity : Detect a 3cm diameter stick at > 2 m
6. Input Trigger : 10uS Min. TTL level pulse
7. Echo Pulse : Positive TTL level signal, width proportional to range.
8. Weight : 0.4 oz.
9. Size : 1.75″ w x 0.625″ h x 0.5″ d
Theory of Operation :
The ranger works by transmitting a pulse of sound outside the range of human hearing.
This pulse travels at the speed of sound (roughly 0.9 ft/msec) away from the ranger in a cone shape and the sound reflects back to the ranger from any object in the path of this sonic wave. The ranger pauses for a brief interval after the sound is transmitted and then awaits the reflected sound in the form of an echo.
SRF04 Datasheet PDF Download