Parallax Laser Range Finder as Altimeter

Does anyone know if this Parallax laser range finder can, or has, been used as a altimeter?

http://www.parallax.com/Store/Sensors/AllSensors/tabid/760/ProductID/774/List/0/Default.aspx?SortField=ProductName,ProductName

I had not seen that yet.  Interesting!  It says nominal range is out to 4' and maximum object detection to 8'.  I assume the max is with excellent reflection.  The update rate is one second which is pretty slow for such short range.  If you're thinking on a quad or something, it doesn't sound very good.  I'll ask them about it.

...Tiger

I didn't pay attention to the range, DOH!  But yes, I was thinking about usage on a quad.  I wonder if they have something with more range that mates with the propeller.

Next time I talk to them I'll ask.  You notice they did not design that one.  They are just selling it.

...Tiger

I did notice they don't make it, but they must have a relationship with the company who does.  I look forward to hearing what you find out when you speak with them.  Cool stuff going on.  Did you see my post that they are selling Parallax stuff at Radio Shack?

If you look close at the board, I think you'll see a Propeller chip.  That automatically connects them to the company.   Anyway, I'll ask them about it and see what it's capabilities really are.  Might also be able to find more going to the manufacturers site.

Yes I did see your posting about Radio Shack.  They have been selling through RS for several years now, but I was surprised to see the Propeller board.  That's a quantum leap from the Stamps they've been selling.  RS also sells some of the bots and a lot of sensors.  I doubt everything is available on the wall in Grants Pass, but they can get the stuff which is cool.

...Tiger

Just took another look at the Parallax page and found the schematic for the rangefinder.  It's just a red laser that comes on once a second and it seen by an OmniVision OVM7690 VGA camera.  Then the Propeller looks at the digital video and triangulates the distance from the position in the horizontal scan.  Kinda clever what they're doing, but I can see it's going to have serious limitations.  I doubt it would be very useful as an altimeter like you asked.  It doesn't work at all like a normal laser rangefinder.  Glad I took a look at this because I had not seen this particular OmniVision sensor before and it's pretty cool.

I sent an email to someone at Parallax to get some feedback on the board.  I should hear back from them tomorrow.

...Tiger

Interesting.  I think we would need more accuracy and a higher sampling rate than 1 Hz...a lot can happen to a helicopter or quad in one second!

It would be nice to have a reasonably inexpensive laser rangefinder that we could trust for hovering and eventually landing.

Just got a response from Parallax.  It's more in the form of a text since they guy is at a trade show and answering on his phone.  It's short:

"Not the right tool for the job.  40" maximum and not ideal for surfaces like grass or dirt, especially when outside."

That's about what I expected.  You could do that with a Sharp sensor for a fraction of the price.  Need a "real" rangefinder.

...Tiger

I thought it was too good to be true.  Thanks for following up on that with them.  I wonder if there are any laser rangefinder solutions that would work well as an altimeter and not cost more than the entire quad?

There are any number of relatively inexpensive rangefinders around but the ones I know of all have the same two basic problems.  First is that they don't work well if they are moving.  The second problem is no I/O to get you connected.  The second problem might be overcome with a little hacking.  It's still probably cheaper to use a pressure sensor for gross altitude and ultrasonics for low level and landing.

...Tiger

Agree.  I think this is a area that needs to be addressed by hobbyists.  It is one significant area that sets our models apart from the professional-grade craft.