Saturday, 16 August 2014

My first lasertag gun

I play a reasonable amount of LARP where we use lasertag  as the combat system. I posted a while back about wanting to make my own gun for this and have made a start on one. So far I'm happy with the progress. Painted up like this it will make a satisfactory vaguely sci-fi looking pistol that can be used in any game where you're not fussed about having replica kit.
The basis for this is a NERF Firestrike for multiple reasons. It's a compact but chunky pistol body and has a 'laser' built in, which shines a red target on things when you push the secondary trigger. This means there's an OK lens unit, battery holder and switch all built in as it comes out of the box and like most NERF guns it's really not very expensive. Building a gun out of a decent Airsoft body is a much more expensive proposition.
Opening it up, there's a ton of space inside, I can't see me having any difficult getting it all in expect perhaps a speaker for the sounds. I'm also conflicted about powering it. The battery holder only holds two AAAs which isn't high enough voltage, I really need a steady 3.3V, preferably 5V or more. So I can either go with a step-up voltage converter or get some of those Li-ion batteries people use for vaping. AAA size but 3.6V each.
After ripping out all the NERF piston stuff the trigger got turned into a switch with a simple tactile button glued in a suitable position. I started hacking the shell about to fit an on/off switch at the rear of the gun but it interfered with this mechanism and I've abandoned that plan. Not sure what to do about an on/off switch now, I may just pop the battery cover off, it's not like tag guns draw a lot on standby.
I used a Dremel to cut the tracks on the small circuit board that connected the battery terminals and secondary trigger. This means I can take feeds separately for power and the switch, originally it just switches the batteries straight to the LED when you push the trigger. I plan to use the secondary trigger for the reload function, it's nicely placed for it and not as easy to push as you'd think.
Then I desoldered the red LED from the board in the emitter and replaced it with an IR one. It's taller so the focus may have been messed up. There will be an element of suck it and see on this.

At this point I've got a trigger, reload switch, battery compartment, emitter and muzzle flash LED ready to go which is getting it down to sticking an Arduino in there and making it work.

However I'm going to pause for a bit. I painted it last night and while I like the silver finish it's still slightly tacky. I've had this with NERF guns before, the paint seems to take ages to dry, which must be related to the solvent getting into the plastic of the body. I know from experience handling it too much will mess it up so I'll leave it a while longer to dry.

This leaves me time to sort other things on my to-do list for it like ordering some of those AAA Li-ion batteries, sorting out a suitably compact sounder, coming up with where to mount an on/off switch, making a status indicator which may just be an RGB LED and building the 'gun board'. The latter is actually the fairly easy bit.

I'd love to leave the USB programming port for the Arduino accessible if I can and maybe have a 7-segment or matrix display but I suspect the latter is stupid 'feature creep' that will drag the project out and make it unnecessarily complex.

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