Hi,
Could anyone advice me on how to build a Laser Distance Meter? Any suggestion on possible circuits and ideas is appreciated. Thank you.
I got the following specs in mind
Distance 1m – 30m , Temp -10c - 50c, All weather, Power Supply 12vdc

 

Welcome to Electro Tech...

Tough project even for advanced hobbyists.

Light moves VERY fast, the time difference between the outgoing pulse and the return "echo" requires some serious clock speeds to meausre.

By contrast sound moves a lot slower and many circuits are to be found for Ultrasonic rangefiders.

The commonly availible transducers are typically good up to 15m, use of a parabolic dish will improve detection range.

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It may seem like a good idea at the time , but never stir your cold coffee with a soldering iron.

 

hi welcome,

What accuracy and what update rates are you looking for.?

Whats your budget.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

I think the usual way for laser is angle or parallax and not time-of-flight. That said, I've certainly never tried to build one.

Here's one interesting site: http://www.eng.buffalo.edu/ubr/ff03laser.php

Here's another page which goes more in depth: http://www.seattlerobotics.org/encod...110/vision.htm

I seem to recall another page from a university project on the topic but I can't find it right now.

As Eric implied, don't expect the project to be either easy or cheap.


Torben

 

Actually, the hardest part is getting the optics focused and getting enough return signal to measure. Commercial laser radars work by firing a series of short pules (~40 I think) and they require 32 or so to come back to the detector. Then it just finds the derivative after doing this enough to get velocity. However, it is not hard to build a simple histogrammer to find the mass center of the return pulse and a couple of repetitions will get you in fairly close.

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Hi,
Thank you all for the replay. Any suggestions would help. Can you tell me what degree Ultrasonic work? (from the midpoint to the outside ) will it detect any other object then the target?

 

hi,
If you going to use ultrasonics, Google for ultrasonic range finder there are lots of developed circuits available.


eg: http://www.robotshop.ca/home/product...ic-ranger.html

Hows the Eskom power problem affecting you.?

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

It depends on the sensor in question. Some have quite broad areas, some are narrower. Search for ultrasonic rangefinders on sites such as http://www.sparkfun.com and read the datasheets to find out more specifics. If you build your own, you will need to find the datasheets for the transducers you are using. There are various ways you can affect the beam width (horns, etc) as well.

If you tell us exactly what problem you're trying to solve perhaps we can be more specific. Right now we're having to guess at what you want.

Yes. The sensor has no brains; anything in front of it which can reflect the beam sufficiently well will be detected. Same with any sensor: the sensor has no idea what *you* want it to see; it only knows what it's pointed at.


Torben

 

Hi,
Why I thought of a distance meter is: want to see where the beam is broken between 1 - 30m and give a signal.

 

So you dont want to measure distance at all.!

Just an interrupted laser beam,?

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

I thought that is the only way to work
Sorry for not replay, busy with welding

 

hi,
When youve put away your welding goggles, tell us what you are trying to do with the laser beam, we may have some ideas.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Hi,
I can’t use any wire from the wall to the other side, that is why I thought of Laser (no transmitter and receiver) Somehow you have to outsmart the criminals, so what will you do? Any thing would help.
Thank you
Piet

 

hi,
You could use a medium power IR laser or IR emitter, with a bicycle type reflector on the far wall and detect when the beam is broken.

Have it about 1 metre from the floor so you don't detect animals.

You could use a commercial PIR sensor in the room, without the light and use the relay output to sound a buzzer.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Hi,
Thanks a million for this advice. Can you help with a diagram?
Piet