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DPRG: Re: information about devices

Subject: DPRG: Re: information about devices
From: Aaron and Hifumi aaron_hifumi at bottle-rocket.org
Date: Mon Sep 20 14:57:11 CDT 1999

Hi all.... just got back from a little 2 month vacation.

I think Jim is right. You are going to have serious troubles with trying to
calculate distance by power output, unless you are in a seriously controlled
and limited (read- unrealistic) environment.

Jim mentions an IR unit that uses triangulation to get a distance measurement.
I think that he is refering to DIRRS, which you can find at
http://www.hvwtech.com/robotics.htm#dirrs  They are made by Sharp. I'm guessing
that the company name that he was trying to think of was hvwtech. They are
based in Canada, so the prices that you see there are in loonies. The price for
one in American bucks is around $26 or so. If you buy 4 of them, the price per
unit drops to $19, which is not to bad. It's funny that they were mentioned on
the list today, as I was just reading about them and thinking about using them
in my current robot project. 8-) Must be a good sign. Or maybe I'm stretching
here. Anyhow, they have a little documentation on the DIRRS on hvwtech's
website (www.hvwtech.com), including a simple diagram of how it works. Perhaps
these two are more interested in building their own version in order to
increase the distances that it works under, they could take a look at just how
the DIRRS works, and go from there. It's probably a better place to start,
rather than measuring power output.

Aaron

Jim Brown wrote:

> At 05:35 PM 9/20/99 +0200, you wrote:
> >We need a system which can emit a modulated IR signal. The energy emited
> will be
> >increased until the receipt signal is recognized. We expect we will be
> able to
> >calculate the distance with the energy emmitted
>
> The problem with this approach is that it relies on the
> reflectivity of the object you are scanning for.  For example,
> if you shine at a glossy white wall or a mirror, you will always
> receive  an ON signal no matter the level of energy you emit and
> at any distance, and the opposite would be true for a flat black
> wall.  Different colors will reflect different amounts of energy.
> The only reliable way to get distance information with
> IR is to triangulate the data and calculate a distance.  There
> are devices like that out there that do exactly that all in
> one package.  I don't remember where I found them, but I think
> their company name was hitech or something like that.  The parts
> run about $25 or so.

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