Ultrasonic Distance Measurement 2

[Paddymagee]

Im looking at a system to detect the distance between a crane and a steel girder(the overhead crane type as seen in factories). The idea is to sound a warning when the crane reaches a certain distance from the wall.
I think the best type of sensor to use is an ultrasonic type (but im open to suggestions)

At the moment we are using infra-red sensors with a bicycle reflector which works fine until something moves out of position. I thought ultra-sonic would mean less setting up.

Im not an expert in these types of sensors which is why I am posting here but I had two possibilities in mind -
(1) Using one sensor mounted on the crane which can "sense" the distance to the girder by bouncing the signal off the girder. I suppose this is like sonar.
My worry here is that the beam is only about 300mm wide (mounted horizontal) so would this setup always work?

(2) Fit an ultrasonic transmitter and an RF transmitter to the beam. Fit an ultrasonic receiver and an RF receiver to the crane.
The Transmitter sends an ultrasonic and an RF signal at the same time.
The receiver picks up both signals and calculates the distance between the two depending on the time lag.

The distance range required would be 1-10m Accuracy of 300mm or so.
I would prefer to keep the cost down so the sensors should be less than £100.00 if possible.

All thoughts and suggestions welcome.

 

[VEBill]

Radio Shack (Canada/USA) used to sell 'parking assistants' intended to help people park inside their garage. They're still around in the dusty corners of some stores. Ultrasonic, settable trip distance, indicating lights. I'm not sure if they'd reach 10m or not.

There are probably better solutions than this sort of an approach. Maybe 'a switch on a stick' sort of thing.

 

[IRstuff]

ultrasonic sensors are generally not effective beyond about 50ft:

http://www.senix.com/models_ts.htm

http://www.constructionbook.com/xq/ASP/ProductID.473/id.448/subID.450/qx/default2.htm

http://www.overstock.com/cgi-bin/d2.cgi?cid=52419&PAGE=PRODUCT&PROD_ID=464998&fp=F&kid=5334

TTFN

 

[europus2002]

Hi Paddy,
you could use reflective IR or LASER. Have a mirror or similar reflective material on the beam placed at 30-45 degrees of angle and reflective optical tranceiver on the wall. The angle to the mirror will help you adjust the sensitivity and immunity to false triggering , thus improving reliability. I had implemented a similar setup in a semiconductors manufacturing equipment for the loading stage of high temperature oxidation furnace...The precision achieved was much better than expected...
Another thing that i could think of is , use a small metal structure to create omnidirectional radiation pattern of IR transmission (sort of flarring the IR radiation in 360 degrees). You can do this by bouncing the light off the surface of the structure(elliptical side wall, illuminating any light reflector from outside and not from inside) so that you get a directive pattern of radiation along X-Y plane...U will have the same ruggedness of Ultrasound but keeping the same precision of IR....Feel free to drop back should there be any confusions...

 

[jraef]

I have done this on bridge cranes. Ultrasonic will not be reliable in my experience. Laser is best in terms of accuracy, but expensive and prone to getting dirt on the lens and ceasing to function. In spite of that there are companies specializing in laser crane detection systems, Google "crane collision avoidance" to see them.

The bets solution I found was infrared, but using a narrow beam proximity sensor, not retroreflective like you described because of that exact problem. Besides the distance, look for one with a feature called "automatic gain control" which punches up the signal as the lens clouds. That gives you more time in between cleanings, which tend to be rare on cranes. STI (Scientific Technology Inc.) is who I used on one big project, excellent products. I have also used Banner (bought out by someone now, can't remember who) and Sick Optics, although I didn't like that one because I got poor support.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[boreholelogger]

Have you looked at

http://www.sick.com?

They have some good gear!.

 

[boreholelogger]

Although the above sensors are not cheap.
So that sort of throws out the $100 sensor idea...

 

[ScottyUK]

Banner were bought out by MTE Turck.