Position sensing using ultrasonic sensors

macrobeak

There are many transmit/receive ultrasonic sensor pairs like Ping.
I want to create a perimeter network of ultrasonic transmitters with one receiver within the perimeter.
The position of the receiver would be calculated by trigonometry knowing the distance from each transmitter.
Does anyone know of discrete transmitter and receiver ultrasonic modules?

Mike Green

All kinds of problems with your scheme. For example, how would you tell which transmitter produced the pulse received by the receiver? If you pulse the transmitters individually and then allow time for any secondary echos to die down, what's the difference from using a PING at each perimeter position? Both transmitters and receivers are very directional. It would be possible to build an omnidirectional microphone for ultrasound, but that's not how they're usually made.

Phil Pilgrim (PhiPi)

You can accomplish what you want by combining Ping)))s with infrared:

http://forums.parallax.com/showthread.php?120038

But, as Mike stated, there is that pesky directionality issue.

-Phil

macrobeak

Thanks Phil, Your idea is perfect. I think the directionality issue can be managed in my setup. The interior of the perimeter is empty except for the target, so the distance perimeter - target should be the first reading.
Mike, the perimeter stations and the target will be connected. Each perimeter station will be fired after some delay in an endless loop. The target will get a distance from each perimeter station.
I will start experimenting and keep you informed.
- 'beak

Phil Pilgrim (PhiPi)

macrobeak wrote:

Thanks Phil, Your idea is perfect. ... Each perimeter station will be fired after some delay in an endless loop.

I think you've missed the point of my idea completely. Firing the stations autonomously in a loop will not work with the Ping))). The robot has to trigger each transponder itself (using unique IR codes), so that its Ping))) can start its timing sequence. The transponders are not, and do not need to be, connected to each other.

-Phil

macrobeak

OK, I will experiment first and see how it develops. I may come back later with some more coherent questions.

macrobeak

1) I have found that it is quite easy to turn the ping module into a dedicated transmitter or receiver by blanking the appropriate sensor. (use a tight cap with cotton wool)
2) I have implemented a one-transmitter, two-receiver positional network using blanked pings and found it to be very stable and accurate.
3) The advantage of using the ping like this is that you do not need to make your own transmitters and receivers (I cannot find any individual modules for sale).
4) It is thus possible to build a position sensing scheme using blanked pings. There is a very good article on the trigonometry mathematics of positional schemes by Larrt Foltzer in the Mar2012 Circuit Cellar.
5) I attach a photo and program for information.
6) Now, my real interst is locating the position of my pool cleaner in my pool. I cannot locate cheap underwater transmitters or receivers - can anyone help?

kwinn

Try looking for ``fish finders``. This is what previous posters seeking waterproof ultrasonic transceivers have ended up doing.

macrobeak

Kwinn, no good - I need the transmitters and receivers separate!

Franklin

http://circuitcellar.com/featured/robot-nav-with-acoustic-delay-triangulation/ might have some ideas.
http://www.futurlec.com/Ultrasonic_Sensors.shtml#TR40-16OA00 have sensor modules.