Ultra sound sensoring

Hi all,

I'm going to make a small prototype ultrasound anemometer. It both needs to survive bad weather and the driver/receiver pair must be opposing each other. This makes me believe that a Ping device is not an option (and besides that I need to run two measurents as close to each other in time as possible so I would like have control over the signalling).
I found the attached schema (next post...) and it's pretty much what I intend to do. But it looks like the sender is connected to several pins, why is that? Is it to drive it from the processor without having another LM386 or similar?

Best regards,
Sven

PS. If someone got another example, I'm glad to be enlightened. :slight_smile:

Here's the example I found:
http://www.shuningbian.net/2009/02/arduino-ultrasound-ranger.php

(I was not allowed to link in my first post)

Looks like the multiple pins are to boost the drive capabilities.
You want to put as much power as feasible into the transmitted pulses, because the burst of pulses should be as short in duration as possible, otherwise minimum range performance suffers.
I think the Devantech sonar devices use just eight cycles of 40KHz for the transmitted burst. (though I suspect the transmitter may ring for a little after anyway)
I've seen some designs use the Maxim 232 drive chips to drive the transmitter.

One question - what principle does the anemometer work on?
Doppler?
If so, I think there are going to be better circuits than the one you showed, which is best suited to measuring time-of-flight of the transmitted burst.
For Doppler, you need to difference the frequency of the transmitted signal and the received signal. Some sort of attenuator (for the strong transmitted pulse) and mixer would be needed.
But I'm happy to be proved wrong. :wink:

It's really simple physically, and there are a bunch of examples out there how to do it with low budget PIC's. Even the industrial models work the same way. And yes, it's just a simple time-of-flight. :slight_smile:
No doppler needed.

I expect the biggest challenge will be finding low cost waterproof transducers of suitable quality. When you do, please post where you got them.

Have fun!

I sometimes get accused of having done all the obscure projects but this is one I have been wanting to do for a long time.

If you have three measurements at right angles to each other then the time of flight will give you the wind vector, so not only do you have the speed but also the direction. Imagen a cube with transmitters at one corner sending out signals along each side and the opposite corner are the receivers.

As Mem says the problem is the transducers, most of the cheap ultrasonic transducers are not suitable for outside work.

Hi again, sorry for my late reply. I almost forgot I started this thread.

I have both transmitters and receivers for hostile environments, but a trans/rec called UTEC4018F is also water resistant. And as a bonus, when I checked the distributors web page I even found a datasheet with a schema in the end: https://www1.elfa.se/data1/wwwroot/webroot/Z_DATA/07302854.pdf
They're are pretty cheap, actually not more than the others they sell.

Three measurements is a minimum to get everything in place. Like Grumpy_Mike says the direction can be calculated too. Most professional anemometers use four points though because the distance is so small that the errors and tolerances gets very big. The mathematics is a little bit easier also. With two axis at 90 degrees the calculations are much more precise, and instruments that a human being can afford can make measurement below 0,1 m/s.

I get accused as well. But I've learned to not listen to it, and in the end I'm the one who have fun. :slight_smile:

Here are some examples on how they look and works.
http://www.gill.co.uk/products/anemometer/2axis.htm
http://www.gill.co.uk/data/manuals/WindSonic%20GPA%20manual%201405-PS-0019%20issue%2016.pdf

Regards,
Sven