One Use for a 1mW Laser Pointer




About: general bloke type of tinkering

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

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.
Coarse adjustments are made via the friction fit ply cradle, and the fine adjustment is done using the threaded weight.
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.

Step 3: More About the Cradle

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.

Step 5: Using to Check the Trueness of a Wing

Checking the trueness of a wing
First sandbag the wing, (to prevent the wing moving) then zero the laser on the center section. Now gently transfer the meter to the wing tips without knocking out the zero setting. As a matter of principle I always face the laser to the back of the wing or plane so that when the laser reads above the zero line it indicates positive degrees.
The laser is very visible in daylight, you can actually see it glow right through the
2mm balsa that I use for mounting the scale markings, unfortunately my batteries have gone flat.

Step 6: The Usual Caution

NB As with all laser devices exercise extreme caution when using and dont look into the device when on, it can damage the eye very quickly.



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    15 Discussions


    6 years ago on Introduction

    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?


    8 years ago on Introduction

    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


    Reply 10 years ago on Introduction

    Sure, why ? Where are you going with that , you could probably take out everything and use it for a usb stick too. :)


    Reply 10 years ago on Introduction

    i was thinking about putting a more powerful diode in it, like what they do in the maglite laser instructable. LG

    IPOD M0dda

    11 years ago on Step 6

    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"

    1 reply

    12 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

    1 reply

    Reply 12 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.


    12 years ago

    This would mean so much more if you explained what an incidence meter is.