I want to make a linear laser distance meter up to six metre
help pls....

 

Buy one! - you're not going to make one.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

I'll bet they are not available in his geographic location. Maybe you could buy one and send it to the dear soul.

 

How would we know?, he's not filled his location it!.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

I think it's a better than even money bet.

 

Hmmm... Interesting little project...
The speed of light is 299,792,458 metres per SECOND...
So if you want to range find over 6 metres, you'll have to have some pretty shit hot timing routines to measure the return trip for the laser pulse!
The round trip time for the laser pulse at 6 metres is around 4.002769142377824594906920573699e-8 seconds!!!
or 0.00000004002769142377824594906920573699 seconds...
Not sure a microcontroller will repond quick enough!

Maybe an ULTRASONIC range finder / radar would be a better project???

__________________
====
Shax.
====

A bus station is where a bus stops...
A train station is where a train stops...
On my desk I have a work station...
Nuff Sed!!!

 

Hello!

In fact it's not that impossible to build one. For sure, trying to calculate the time of flight is nearly impossible... (at least it's impratical). The typical way is to do trigonometry: you send the laser with a small angle and you receive it on a CCD. The position of the spot gives you an angle that you compute to know the distance.

Search the web, there are some hacks with laser pointers and webcam. Sure it's not industrial grade but it can be enough for some projects.

__________________
JFDuval
jfduval --@-- aqra.ca
http://www.aqra.ca

 

hi,
If you want to build a low power pulsed laser to measure from say 0.5mtr thru 10mtr you can do it this way.

At the instant the laser diode is pulsed, set a 74F series monostable, start a fast run down linear voltage ramp.
On receiving the laser echo, reset the TX M/S and start a slow [*100] ramp up to zero volts of the TX ramp down voltage.

From the instant the RX echo pulse is detected start a 15MHz counter and stop the counter when the ramp up reaches 0V.
In the counter chain you have a count proportional to double the distance measured.
By chosing the 15MHz xtal [ speed of light is 300,000,000/sec] the counter chain gives a transit time count of 100* the actual transit time.

If you require more details please ask.

__________________
Eric
"Good enough is Perfect"

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

 

So, using TRIG, what happens if the reflecting surface isn't at EXACTLY 90 degrees to the incoming beam? I'm sure that would cause some error in the result......

__________________
====
Shax.
====

A bus station is where a bus stops...
A train station is where a train stops...
On my desk I have a work station...
Nuff Sed!!!

 

Hello!

I have the same question that you. I didn't investigated far enough to find an answer.

For sure this solution is viable, it's what is used in many commercial rangefinders. I just don't know how they deal with that angle.

__________________
JFDuval
jfduval --@-- aqra.ca
http://www.aqra.ca