SRF04 Ultrasonic Range Finder. 30th September Introduction. The Devantech SRF04 Utrasonic Range Finder of- fers precise ranging information from. 28 Jan SRF04 datasheet. Description: The SRF04 was designed to be just as easy to use as the Polaroid sonar, requiring a short trigger pulse and. The Devantech SRF04 ultrasonic range finder provides precise, non-contact distance measurements from about 3 cm ( inches) to 3 meters ( yards).

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The beam srf04 datasheet of the transducers used on the Srf04 datasheet, taken srf04 datasheet the manufacturers data sheet, is shown below. The echo signal will appear datashheet the same pin as the srf04 datasheet signal. It then listens for an echo, and as soon as it detects one it lowers the echo line again. Update – May Since the original design of the SRF04 was published, there have been incremental improvements to improve performance and manufacturing reliability.

If nothing is detected then the SRF05 will lower its echo line anyway after about 30mS. It is much harder to tell the difference between this direct coupled ringing and a returning echo, which is why many designs, including the Polaroid module, simply blank out this period. This pin is pulled high by default and datawheet left unconnected, the timing remains srf04 datasheet srv04 before.

Devantech SRF04 Sonar Ranging Module

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. A convenient negative voltage for the srf04 datasheet and comparator is generated by the MAX Up to 1mS depending on when you decide it has stopped.

The transducer can handle 20v of drive, so I srf04 datasheet to get up close to this level. In operation, the sfr04 waits for an active low srf4 pulse to come in.

The new code has shipped in all SRF04’s since the end srf04 datasheet April Changing beam pattern and beam width You can’t! This is because the Stamps take progressively longer to look at the higher numbered pins and can miss the rising edge of the echo signal. When left unconnected the SRF04 behaves exactly as it always has and is described above.


To use this mode, just leave the mode pin unconnected – the SRF05 has an srf04 datasheet pull up resistor on this pin. As and example of the sensitivity of this design, it will detect a 1inch thick plastic broom handle at 2. The SRF05 can be triggered as fast as every 50mS, or 20 times each second. The SRF04 srf04 datasheet designed to be just as easy to use as the Polaroid sonar, srf04 datasheet a short trigger pulse and providing an echo pulse.

With the timing pin pulled low grounded a uS delay is added between srf04 datasheet end of the trigger pulse and transmitting the sonic burst.

SRF04 Technical Documentation

The 10uF srf04 datasheet is now 22uF and a few resistor values have been tweaked. Range is increased from 3 meters to 4 meters. I therefore shut it down whilst listening for the echo. The echo line is then raised to signal the host processor to start timing. Since the echo output is not raised until the burst is completed, there is no change srf04 datasheet the srf04 datasheet timing, but the uS delay gives the Picaxe time to sort out which pin to look at and start doing so. Looking at the returning echo on an oscilloscope shows that it is much larger in magnitude at close quarters than the cross-coupled signal.

The 5v drive can give a useful range for large objects, but can be problematic detecting smaller objects. It then generates just eight cycles of 40khz. The beam pattern of the SRF04 is conical with the width of the beam being a function of the surface area of the transducers and is fixed. Mode 2 – Single pin srf04 datasheet both Trigger and Echo This mode uses a srf04 datasheet pin for both Trigger and Echo signals, and is designed to save valuable pins on embedded controllers.

Here is the schematic, You can download a better quality pdf k version srf1. This project started after Srf04 datasheet looked at srf04 datasheet Polaroid Ultrasonic Ranging module.

The n capacitor C10 is datasheett to about —6v during the burst. Datashedt echo line is therefore a pulse whose srf04 datasheet is proportional to the distance to the object. The beam pattern of the SRF05 is conical with the width of the beam being a function of the surface area of the transducers and is fixed.


The SRF04 will send out an 8 cycle burst of ultrasound at 40khz and srf04 datasheet its echo line high. The input capacitor C8 blocks some residual DC which datashete srf04 datasheet to be present.

After a while — no more than mS normally, the returning echo will be detected and the PIC will lower the echo line. The SRF04 Timing diagram is shown below.

The circuit is designed to be low cost. This is to ensure the ultrasonic srf04 datasheet has faded away and will not cause a false echo on the next ranging. The problem of getting operation down to cm is that the receiver srf04 datasheet pick up direct coupling from the transmitter, which is right next to it.

In this case you can connect the “do not connect” pin to ground and give it an extra uS to get there.

After programming its just an unused input with a pull-up resistor. You only need to supply a short 10uS pulse to the trigger input to start the srf04 datasheet. If the width of the pulse is measured in uS, then dividing by 58 will give you the distance in cm, or dividing by will give the distance in inches.

This is close the 25 maximum gain available using the LM Unfortunately, this also generates quite srf04 datasheet bit of high frequency noise. You only need to supply a short 10uS pulse to the trigger input to start the ranging.

srf04 datasheet

The SRF04’s “do not datasheef pin now acts as a timing control. The SRF04 provides an echo pulse proportional to distance. This is a question which crops up regularly, however srf04 datasheet is no easy way to reduce or change the beam width that I’m aware of. Srf04 datasheet echo line is srf04 datasheet a pulse whose width is proportional to the distance to the object. The raising of the echo line also shuts of the MAX