Dme

Does anyone know where i can get a cheap DME that can go from 0 to about 120 feet? I need it to measure distance between vehicles.

Dwayne

Hello,

Unfortunately, I can't find any information about what is the best way to measure distances from 1 to 10 meters. Like Dwayne, I'd like to measure distances between vehicles.

I assume the use of a LASER diode is the way to go.

There is no need for high accuracy; plus/minus 10 centimeter is acceptable.

I was thinking about generate a laser pulse and, in the same time, have another element "looking" at the spot and mesuring the time between the "laser switch-on" and "I can see the spot".

How is it realised in those meters one can find in the stores?
http://www.leica-geosystems.com/imag...2keyvisual.gif

Hi, flotul

Question 1)

How much is speed of light ???

Question 2)

Let's suppose 30 meters from the target: how many time will it take for the beam to make twice the distance ???

Question 3)

Is it compatible with PICBasic Pro time measurements ???

Question 4)

Is it compatible with PIC 32 Bits ( @ 80 Mhz ) capture units ...


Too bad !!!

Alain

PS for Dwayne : Cheap and Laser do not match ... till the day !!!

The low cost DME I have found in hardware stores have a laser as a pointing guide but do the actual distance measurement with ultrasonic sensors.

Expensive systems, like Dimetix, Rockwell and others are true laser DME but are hundreds of times the hardware store price.

HTH
Brian

Thanks BrianT,

It didn't know that these devices wouldn't use the laser to do the measurement.

Let's find the ultrasonic sensors then...

Hello,

I'm looking now for ultrasonic distance sensors. Speed of Sound is far more in a PIC's capacity range than "Light Speed" (;) Alain).

My search by DIGIKEY, DISTRELEC, FARNELL, REICHELT, CONRAD and lots of suppliers one can find in the internet, but I'm unsuccessfull.

I found ultrasonic sensors for distances up to 37ft (11 meters) which is almost okay but their price is high (> $500.-!!!).

Does anyone have a suggestion where I could find those elements?

Is there another "electronic" way to measure 1 to 10 meters distances?

http://www.acroname.com/robotics/parts/c_Sensors.html
Devantech
Parallax

HTH
BrianT

For giggles and grins...

Light travels at about 1 foot per nano second.

Kick a PIC at say 50mhz (skimask says it's "ok")

Tcy is 1/4 clocking speed or 12.5 mips or 80 nano seconds.

One Tcy = 80 feet or 40 feet out and back round trip, so 40 feet would be the step resolution using time counting.

Now, clock that PIC at 4 Gigs and you can be down to 1 foot resolutions (just before that billionth of second when the PIC releases its magic smoke). ;)

At 50mhz, it could be interesting to see just how high that airplane is flying (NOT!), give or take 40 feet. Kids, don't try this at home. We are professionals.

Thanks BrianT,

Your link is great, especially that one:http://www.acroname.com/robotics/parts/R11-6500.html.

As almost always, particular modules and parts exist but finding the correct wording for a good web search is sometimes the most difficult thing to do - Ranging Module was the key.

I already ordered one part - getting ready to play with it ;)