This was something I put together for a colleague at work who is into his Air soft guns.
We were talking and he said it would look cool for his night games if he had a Predator style laser site for his rifle.
So, I looked on eBay and found some red laser modules that run on 3.4V at around 17mA each. To keep it quick, simple and easy to both assemble and to fudge about later I chose an adjustable DC – DC converter to drop the voltage from a 9V PP3 battery. This also allows you to tweak the voltage to get the best results.

1 x Plastic housing that will fit to the barrel / stock
1 x 9V PP3 battery
1 x battery clip
1 x switch
1 x DC – DC converter
5mm plexy or acrylic
3 x laser modules.

Step 1: Mark and Drill

First mark the size of the end of the plastic housing onto the plexi, then make a triangle that will end up inside the housing once you drill through.
The laser heads I had were 8mm diameter, so you simply drill the 8mm holes in the plexi. Cut it out and round off the corners. Use this as a template for the end of the housing, then open those holes up to around 9mm to make the assemble easier.

Step 2: Assemble and Align

Solder the lasers to the output of the DC-DC converter and the battery clamp (via the switch) to the input. Don't forget to put the wires through the holes in the housing.
I then placed them into the plexi and had a test run, I found that to form the familiar triangle pattern all I had to do was rotate the laser heads, this gave a good even look to it.
I used a spot of super glue to hold them in place, this is where I found out that the back of the laser diode is open and not a sealed unit as I had first thought :-(

So, once you have removed the one that is now full of superglue and replaced it with a new one, then re aligned them again, wait for the glue to dry.
Pick it up too soon and for some reason it is very hard to put down, who knew?!?
Once the diodes are set you can dab more glue to the plexi and slap that on the end of the housing.

Step 3: Seek and Destroy!

Then it is all a case of fixing the bits inside the box, putting a bit of black electrical tape around the end to make it look a little prettier and stick it to the gun.
Just remember that if the person you are playing against then covers themselves in mud you won’t be able to see them. It’s true; I saw it in the film!
I shouldn’t have to say this but I feel like I must, the idea is to have fun, not damage someone’s eye sight by shining it at their face.
Kind of ironic when it is attached to the side of a gun that shoots small balls of plastic!