Author Topic: DIY Laser Rangefinder  (Read 5616 times)

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Offline GalacticNerdTopic starter

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DIY Laser Rangefinder
« on: June 15, 2010, 08:46:42 AM »
Hello, for my robot I am planning. (The photovore I mentioned in another topic of mine) I was thinking of a next challenge after I get the mentioned photovore code working.

Of course using photodiodes as obstacle sensors has more disadvantages than advantages, so I was thinking more in the line of Rangefinders.
The first ones I took a look at were the sharp rangefinders. They are pretty popular, but have disadvantages such as the small beam, and the fact you need multiple (or a servo to rotate it) to look at various directions. For a cheapskate like me, that could be very pricy.

Now, searching the web, I stumbled upon this; a diy laser rangefinder. (http://letsmakerobots.com/node/2651) If you take a quick look at how it works, you'll notice it has a lot of advantages. Has anyone ever made one, or used a device like this? Could anyone tell me if this is doable? All components look pretty cheap, I can get them in my local electronics store, whereas I would need to pay tons for shipping for sharp sensors.

Oh btw, I don't have an oscilloscope, so would I be able to debug it without one ?

Offline waltr

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Re: DIY Laser Rangefinder
« Reply #1 on: June 15, 2010, 09:48:49 AM »
Did you read the entire article and the comments?
This would be a great advanced project but not a way to get something better than a Sharp distance sensor if building a Bot is your prime objective. As stated in the article this LASER range finder has a narrower beam than the Sharp. It is also a lot larger, heaver and uses more power than a Sharp.
And yes, you will need an O'scope to get this project working.

Offline Soeren

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Re: DIY Laser Rangefinder
« Reply #2 on: June 15, 2010, 04:27:37 PM »

And besides what waltr mentioned, I would add...

Yes, the guy who made it has... Well, made it and so, it's doable, but he moved on to a better version.
You would do wise in using off the shelf components until you have the experience to decide for yourself what you are able to do, as nobody else have a chance of knowing your skill- and experience level.

If I was to make something like that, I'd first consider how many degrees I wanted it to cover (in integer parts of 360°) and then make an über balanced  polygon mirror on a fast rotating spindle (the faster the better).
Some of the large and fast photo copiers have got a polygon mirror integrated with a motor going around 40,000 RPM, and that would be a nice unit to build on.
For best effect, you need prisms as well, as both in- and out going LASER beam needs to be coaxial, so you need to be fluent in optics as well as electronics and fine mechanics to pull this off.

The thing is that you probably don't need it. A Sharp sensor will tell you when you need to act - if you build a sensor that finds obstacles 50 meters out, you're far to far away to act upon it anyway, at least until you build a 'bot that covers that distance in between 10 and 50 instructions time, which on a slow 1MIPS controller will be around... Never.

If you wanna build it for the fun of it and for getting your own construction experience, go nuts, but if you want stable navigation, go with the Sharp or similar.

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline GalacticNerdTopic starter

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Re: DIY Laser Rangefinder
« Reply #3 on: June 16, 2010, 12:12:42 PM »

Thanks for the info guys, I was just looking for alternative/cheaper sensors, and this seemed quite nice at the time. But you're right, it's pretty much undoable.


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