PING! Can ultrasonic work like this?

VonSzarvas

Hi all,

Imagine a plastic drain pipe. Imagine PING shrink-wrapped to the side...

Would the PING notice something running up the tube? Not a spider I guess, but maybe a rat?

Or would the outside side of the pipe the PING is strapped to be basically where the ultrasonic signal will stop?

Strange question no doubt... any ideas? Thanks all!

Post Edited (Maxwin) : 8/23/2007 10:05:09 AM GMT

pwillard

In my experience, Ping has issues with sound wave reflections from nearby objects (like the walls of the drain pipe in this case). These refelctions would likely make readings inaccurate and variable thus making it's ability to notice an object passing greatly diminished.

This sounds more like a good application for a laser sensor or an optical sensor, like the kind used in industry to validate that a part just passed a certain point on an assembly line.

The PING))) is really cool though... I hope you got one to just play with.·

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There's nothing like a new idea and a warm soldering iron.

VonSzarvas

I was thinking of installing it without cutting a hole in the pipe for the sensor transmitter/receiver. Somehow it just straps on the outside so as not to interfere with what it monitors. Would a laser sensor "see through" plastic or metal tubes?

If I calibrate the normal installed situation, then detect any variance from that, maybe it can be accurate enough... I will defiantly order a PING or two to play around with.

I was thinking that because the sensor is strapped to the pipe (ie. less than the suggested 3cm minimum measuring distance), then we may get 2 echos. An almost immediate echo, followed by a slower/later echo which has bounced off the other side of the pipe. And perhaps the weaker echo could tell something....

Hey, maybe I could mount 2 PINGS, 1 either side of the pipe. And have 1 ping send the signal to the other, then the other PING back again....... lots to try...

[noparse]:)[/noparse]

Bean

Maxwin said...
Hey, maybe I could mount 2 PINGS, 1 either side of the pipe. And have 1 ping send the signal to the other, then the other PING back again....... lots to try...

I think that would be the better setup. One sending and one receiving. You might try triggering them with different delays between them. I would think trigger the receiver, then wait a short time and trigger the sender.

I think the receiver will block the reception of it's own echo because it is so close. So you should be able to time the senders pulse (the receiver will think that the sender pulse is it's own echo).

Like you said, lots to try.

Bean.


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Franklin

Sonar depth finders on boats are mounted to a spot on the hull and "see" through the hull but the ping will probably have problems with the close proximity most.

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- Stephen

LilDi

You could try an inductive proximity sensor. It would be able to see through the plastic pipe and detect a mouse. Problem is, it probably will activate when water is flowing through the pipe as well.

http://www.bik.com

OR parallax Touch Sensor maybe

http://www.parallax.com//detail.asp?product_id=604-00038

Post Edited (LILDI) : 8/23/2007 10:59:55 PM GMT

D Faust

Might you be better to mount an led on one side and a photoresitor on the other? (I DID read the title)

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VonSzarvas

The issue with mounting the led/photoresistor is that (as I understand) holes would need to be drilled in the pipe for them to see each other. That is not an option in this case.

The inductive proximity sensor sounds interesting, however the zip file from that webpage is no longer available for download!

I will try to order a parallax touch sensor just to learn how it works (if I can source the -40 C version), but I think for this project it will fail because of the self-calibration timeout. I could not find on the docs yet how long the period is, but it seems it cannot be disabled, so if (as LILDI suggests) water is flowing through the pipe for a long period, the device would keep self-calibrating!

thanks all for your good input.

Lawson

The LED/photo-diode might not need any holes drilled in the pipe. If the right light frequency (color) was chosen, the PVC pipe will be translucent or transparent to the light.

The inductive sensor could be as simple as a coil of wire around or near the pipe. The PE labs have an example of how to make inductive sensors with the Propeller.

A single PING! may still work, if the ultrasonic transducers are de-mounted, glued to opposite sides of the pipe, and wired back to the ping board. The ultrasonic sensor Sparkfun sells might also be an option in this case. It offers object detection down to zero range. www.sparkfun.com/commerce/product_info.php?products_id=639 Really though the best type of ultrasonic sensor for this case is one that measures how well an emitter and dectector are coupled by the pipe-water-rat system. (aka path loss) Sweeping through a large band of frequencies might be a good idea too.

my 2¢,
Marty

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D Faust

What about cutting out the sections of the pipe and mounting transparent peices of plasic/pipe to the outside and then having the led photoresitor combo? What about a metal detector? You could mount it on one side of the pipe and a magnet on the other. If the detector cannot find the magnet then there is a disturbance.

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LilDi

I've got it!!

Put a cat in the sink and a mesh cage over the sink so the cat don't run away.

Put you Basic Stamp microphone next to the sink and when your Stamp hears a blood curtling screeech,

thats your mouse.

OzStamp

Hi

I reckon the QT113D sensor Parallax have in their "accessory"·· sensor section
would do the trick.

Wrap some alu foil around the pipe connect to the foil with some wires
this creates a large field type capacitance sensor..

See the docs on that sensor and study the manufacturer website that makes that sensor>

I see somebody suggested an inductive sensor .??
An inductive will not work unless your rate is made from
some sort of metal .. steel·· alu·· etc etc.

Cheers

Ronald Nollet·· Australia