Step 1: Equipment and Materials
Red and Black solid core wire
Hot Glue Gun
Rosin Core Solder
120 Ω Resistors
Red 14 milliamp led
Auger or Drill
Philips Head Screwdriver
Step 2: Assembling the Magazine
Looking at the Diagram, I have drawn out the underlying circuit of the project. The circuit consists of a battery, LED, resistors, and wire. The 45 degree lines indicate places where a bridge can be made, allowing resistance to change depending on how far up the line the connection is made. This component is the magazine.
To start, load darts into a nerf magazine, marking every position the bar in picture five lands, like in picture two. Mark along the edge of one of the plastic rays going up the side of the magazine, as this will make integrating the electronics easier. One problem is that if the electronics stick out too far, then the magazine will fail to load.
After making the marks, use the auger or drill to drill all the way through the magazine. Make sure you do not drill through the bar! Ensure that the holes are in a straight line, as in picture three. The holes should be as small as possible, preferably only wide enough for two pieces of wire.
Then take five of the 120 Ohm resistors, bending the wires so that the go into the holes and back out. Once each hole has wire going in and out, solder the wires together, forming soft lumps in the holes. These are supposed to be the contact points, so try to keep them as smooth as possible. In addition, because the darts must travel past these, any sharp points will catch the darts and prevent them from moving in the magazine.
Create a similar set of contacts by curving a wire through the holes on the other side, like picture six and seven. Because it is easier to make this part, if any changes must be made to contact depth, make the changes here.
To create the bridge, use tin foil to wrap around the sliding bar where the contacts are, like picture five. This allows current to move from one side of the magazine to the other.
Finally, hot glue everything down to the magazine, taking care not to be too lumpy. If the glue is too lumpy, it will not slide back into the gun.
To make the contacts, bend soda can strips around the wire and hot glue them into the plastic ledge that meets the bottom of the magazine well.
Trim the can into a more formfitting shape and slide it into the magazine well. If it fits, move on to the gun!
Step 3: Making the Gun!
To begin, I cut lines into the gun where I will run wires, then deepen them into trenches. These channels give the wire some support, and give the glue a foundation. These channels run from the magazine well up toward the gray slider, then horizontally back toward the stock. The negative wire then goes up to the top of the gun.
Then, I run the wire through the trenches, stripping a large portion at each end for the contacts and the battery or led. Once the wire is in the right shape, I hot glue the wire into place, pressing the wire down with the hot glue.
Adding the contacts at the bottom of the well, I told strips of tin can into the stripped portion of wire, and wrap around past the edge of the magazine well. Hot gluing the can onto the gun, the contacts should connect to the ones on the magazine. Slide the magazine into the well to verify.
Next, install the battery. First, I soldered some wires onto the ends of a triple a battery. User aduy did a good instructable on this, which I refer you to. Disassemble the large square portion of the stock that clips into a spare magazine. Cut two notches into the box for wire access, and place the battery inside with the wires sticking out. Take note of which wires are which, as when the led is installed it matters. Then, place some tissue into the box and seal it back up. This keeps the battery from rattling around inside.
Finally, connect a wire from the battery to the positive wire. Solder the led into the negative wire, with the led in the right direction, and connect the other wire to the other lead of the led.
Now the gun forms a broken circuit. If the magazine is inserted empty, the led should turn on. Point the led toward your eye so it is brighter and forms a sleeker profile.