Fake security laser scanner

Thread Starter

cmartinez

Joined Jan 17, 2007
6,593
I want to build an extremely cheap (but fancy-looking) laser device that mimics a security scanner of sorts. My plan is to buy inexpensive laser diodes, install them on top of small step motors, and have an MCU randomly rotate the laser diode around to give the impression that its doing a sensor sweep.

I found these diodes in amazon, and they're being sold as "modules" that run on a 5V power supply. My first question is, is a driver needed to power this thing? or will a plain old 7805 regulator suffice for this purpose?

upload_2018-10-23_8-44-30.png
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,593
There are Q&A at the bottom of the page. Looks like they run directly off of a voltage source. Likes the cat and dog comment. :)

Ken
Ah! ... I failed to notice the comments at the bottom. There was another page with a similar product that had no comments on it, so I didn't bother to check this last page more thoroughly.... and yeah... that comment about the cats and dog was funny :)
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,593
There is an about 90 ohm resistor in series with the diode. That's your "driver".
o_O wow ... these guys really walked the distance with their sophistication... :rolleyes:

The comments say that the lasers work fine, and have a long life expectancy ... maybe if I were to run them at 4V (or if I were to add another 10 ohm resistor in series with the 5V supply) they'll work almost as bright and for a much longer time?
 

wayneh

Joined Sep 9, 2010
16,114
I think moving a mirror around might give a better look, since that’s how laser scans are usually done. I think? The mirror can be tiny and with very low mass, and thus can be moved very rapidly. Maybe they even rotate, and you just change the aperture to restrict the dispersion angle.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,593
The use of a mirror sounds like a good idea. I don think a polygon would be necessary, though. I've done some searching for "small laser mirrors" and came up with nothing. That is, the search results were all about professional and expensive equipment. Where can I find a small "first surface" (read: no mirrored glass) type of mirror?
 

KMoffett

Joined Dec 19, 2007
2,770
I was thinking of making a polygon block out of wood with a hole in the center for the motor shaft. Then glue small mirrors or polished metal squares to the sides. Nothing fancy.

Ken
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,593
I was thinking of making a polygon block out of wood with a hole in the center for the motor shaft. Then glue small mirrors or polished metal squares to the sides. Nothing fancy.

Ken
I was thinking in non-fancy terms too ... it's just that I don't like the idea of using a glass mirror for this application. Polished metal squares sound fine, but where can I find them? Or do I have to polish my own?
 

ericgibbs

Joined Jan 29, 2010
8,841
hi cm,
Old DVD disk, use a strong pair of scissors, cut to suit, poly glue.
E
BTW: some of the Laser diode beams are not pin point dots, bit of a spread in coverage.
 

DickCappels

Joined Aug 21, 2008
5,928
Hard drive discs are front surface mirrors for all intents and purposes DVD and CD discs are diffraction gratings and that may be a problem.
 

Bernard

Joined Aug 7, 2008
5,283
Second surface mirror worked as well as first surface mirror . A section of shiny brass was gust as good.
De-inked beer cans contact cemented to a stiff flat surface almost as good as a optical flat.
Spot can be refocused by rotating back & front sections; spot at 1 ft. 2 mm & 30 mm at 25 ft., on re focusing spot shrank to 12 mm at 25 ft.
Body, red lead is +, blue lead is - on my modules.
Out of 4 modules, 3 were good but with some spot distortion , one is weak.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,593
Second surface mirror worked as well as first surface mirror . A section of shiny brass was gust as good.
De-inked beer cans contact cemented to a stiff flat surface almost as good as a optical flat.
Spot can be refocused by rotating back & front sections; spot at 1 ft. 2 mm & 30 mm at 25 ft., on re focusing spot shrank to 12 mm at 25 ft.
Body, red lead is +, blue lead is - on my modules.
Out of 4 modules, 3 were good but with some spot distortion , one is weak.
I just remembered that I have a piece of polished decorative aluminum lying around. I'll be doing some testing and get back here with the results. Thanks all!
 
Top