Everyone wants to hack a laser tape measure for aircraft navigation.  It would indeed make a cheap, extremely accurate, reliable altimeter.

Today, it's the DLR130.  It outputs at 1cm accuracy at 3Hz.  You need 10Hz for flight, so maybe there's a way to speed it up.




It's very well constructed.



The battery contacts must be desoldered.



The keypad must be removed.


A 100uF 16V cap didn't survive the operation.  It got hung up on a protrusion on the battery side.  The optics & keypad are integrated in the same frame.  It's much lighter than the complete package.



 The LCD could be removed to make it lighter, but never reattached.



A solenoid shutters the laser every few seconds, for some kind of calibration.


The LCD is held on by double sided tape which must be carefully pried without shattering the LCD.


The emitter & receiver have different filters.



The laser used for aiming it also seems to be the laser used for ranging.  The keypad & processing board occupy the same space, so it couldn't be stripped down any further. 

The magic is done by the CF325.  The internet got nowhere with it.  There's obviously a very simple measurement result going to the ATMega169.  The entire left half of the circuit board could probably be omitted, but the update rate is probably limited by the CF325 instead of anything programmable.




The reflected light goes into this magic device.  Years ago, this used to be a giant tin can.  Years before that, this was a 1lb device.

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Comment by Joshua Johnson on January 6, 2014 at 3:01am

Jack you truly are a wizard and a genius with Tech!  You remind me much of myself.  I love taking things apart and figuring out how they work.  I just hope you're more skilled in putting them back together then I am! lol

Comment by Jack Crossfire on January 6, 2014 at 3:08am

The solenoid probably shutters the sensor rather than the laser for calibration.  It creates a gap in the readouts.  Other laser altimeters have been covered on diydrones:

http://www.flir.com/cvs/cores/view/?id=56598

http://diydrones.com/forum/topics/lightweight-low-cost-laser-altimeter

Comment by R. D. Starwalt on January 6, 2014 at 5:06am

I hope you picked it up at garage sale/flea market prices.

In the interest of learning and science, $30 (used) to $90 (new) could buy a lot of tacos. ;)

Once you are down to the emitter/sensor level, the real fun begins. Break out the O'scope!

-=Doug

Comment by Martin on January 6, 2014 at 5:11am

I've read about several unsuccessful attempts of interfacing a range finder with a PC/uC. I think it's a waste of time.

I think the most successful project was where they listened in on the data sent to the display controller.

Jack's second link points to an altimeter that is low cost, has an accessible serial interface and is small. That can't be said about any of the cheap rangefinders.

Comment by Daniel on January 6, 2014 at 5:14am
Comment by John Githens on January 6, 2014 at 9:48am

Among the many comments in that Hackday page mentioned by Daniel above, is this one. I've had an inexpensive Ryobi range finder sitting in a box for a while, thinking it might be hackable. But that's way down on my list of things to do.

Comment by Martin on January 6, 2014 at 9:57am

Among the many comments in that Hackday page mentioned by Daniel above, is this one.

8 feet might be enough for a multicopter, but it's pretty useless on an airplane. Not to mention the 1 Hz sampling rate.

Comment by Don LeRoi on January 7, 2014 at 6:00am

I think a tear down of this one may be the ticket:

https://www.youtube.com/watch?feature=player_embedded&v=N9Lap_V...

Comment by Ravi on January 7, 2014 at 9:29pm

i think someone needs to work on it since now we have 4th generation pixhawk autopilot. once the code is written  then range of laser can be increased by changing the hardware. low cost lasers can have range of upto 500 meters which is sufficient to fly multirotors. a very useful project for the DIYdrones community. keep it up jack!

Comment by Martin on January 9, 2014 at 1:24am

Ok, it seems that there is at least one range finder that is hackable --> http://blog.qartis.com/arduino-laser-distance-meter/

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