# One use for a 1mW laser pointer

Use as laser incidence meter, to measure the angle of attack of an airfoil in degrees.
Mostly on model planes when setting up the wing.
commercial unit here Accupoint
Remove these ads by Signing Up

## Step 1: The meter's components

the meter consists of:

1. the body, (simple aluminum curtain rail) to attach the othe components
2. the freely swinging laser cradle
3. the legs (for gripping surfaces)
4. the scale (marked in degrees)

Firstly the legs, made out of scrap wood and miscellaneous hardware for the swiveling action.

## Step 2: The laser cradle

I used bearings from an old armature off an electric motor for the laser to pivot on, and glued (CA) the armature shaft to the laser body. This way the laser swings freely for accurate measurements.
A bit of heat formed perspex keeping the lasers push button on for use, a quick rotate of the perspex and its off. Sweet and simple.

these pics show the fine and coarse adjustments as well as the amount of coarse travel

## Step 4: The Scale

The critical part of any meter is the indicator scale. This one is dependant on the length between the laser pivot and the scale.

For example, on my piece of track, the distance between the laser pivot and scale is exactly 745mm so that would equate to 1degree at the laser being 13mm at the scale.

This I sucked out of Modern Mathematics for Std 8 by J.J. Dreyer.
In the trigonometry section it says tan theta = opposite /adjacent side

So in my example the angle I want is 1 degree, the side b we have already said
was 745mm and we're looking for side c the opposite side.
Therefore c = tan 1degree x 745mm = 13.0040mm according to Bills calculator.
Bobs yer uncle, an accurate laser meter to a 1/4 degree for less than a tenth of the cost of the commercial unit.
Of course you could make the track longer for greater accuracy, the commercial unit is 508mm long, but dont forget to take flex into account, it just might reduce the accuracy of the unit.
MrOddjob1 year ago
This is mind boggling stuff! You've got to be dedicated to go so far into the aerodynamics etc to ensure the right result. Absolute magic!
I once used two of these Laser Pointers powered in parallel by a 'Wall Wart' in conjunction with a pair of 'Schmitt Trigger circuits powered similarly to receive the beams via a Pair of LDR's. It enabled a cheap adjustable dual Light Barrier for a 'Saw & Drill Line' in a steel fabrication plant. The uses for these simple cheap items are amazing. The cost of a commercial light barrier (£2300). The one I made which did the same job, (£180) amazing! There must be a billion more uses these things can be used for. Any offers?
lsutigertuff2 years ago
Awesome!!!
raghav.kukreti3 years ago
after a month IPOD M0dda"dammit I'm blind...
WPee4 years ago
Setting up a TRUE ZERO reference point is important. The airfoil LEADING EDGEs and the TRAILING EDGEs are center-positioned differently due to the wings edges. The clamps used to establish ZERO need a bit of work to keep them TRUE. My guess is this meter works just fine
lemminggenocide5 years ago
could you take out the diode and use it as laser housing
petercd (author)  lemminggenocide5 years ago
Sure, why ? Where are you going with that , you could probably take out everything and use it for a usb stick too. :)
5 years ago
i was thinking about putting a more powerful diode in it, like what they do in the maglite laser instructable. LG
pindalanderz6 years ago
it's cheaper to just buy a new laser than to buy new batteries.
jackuroo6 years ago
cool
sjoobbani6 years ago
WoW Ur uh..............
IPOD M0dda7 years ago
ahaha i do it all the time. this is exactly what i do. "hey guys check this out "pulls out a 5mW laser points in my own eye FUNNNNN"
6 years ago
ha ha ha love it
petercd (author) 8 years ago
They are used to measure the angle of attack of an airfoil in degrees. Mostly on model planes when setting up the wing, some designs call for a positive angle of attack or none at all i.e. 0 degrees
8 years ago
Well that great, but how do you use it? I've seen those things in hobby magazines before, and they always confused me as to how they work.
spinach_dip8 years ago
This would mean so much more if you explained what an incidence meter is.