If you fancy a Star Wars rebel trooper blaster pistol, you have basically 2 commercial options. There is a blue plastic dart gun by Hasbro, or a great looking, solid but non-functional $400 model from Master Replicas. Neither of them shoot bolts of red light accross the room.
I wanted one that really "worked" and looked good, so I made my own. The project was more about learning electronics than anything else, but in addition to the new understanding of how to build blinky lights, I ended up with a pretty neat toy. I modeled mine after a Hero (that means it was used for close-ups) ROTJ Blaster prop that recently sold on ebay.
The blaster build consists of 2 sub-projects : building the electronic effects, and making the gun itself.
The circuitry is pretty basic and was my first real scratch-built electronic project. It involves a 555 IC timer circuit to trigger the sound and LED effects, and a 4017 decade counter chip to make the LED chaser effect seen at the rear of the gun.
The chassis of the blaster is made from PVC and aluminum tubing, some sheet aluminum a real scope and grip and a few other doodads.
Step 1: Electronic Effects Overview
In order to keep the effects synchronized and of a consistent duration, each trigger pull will set off a one-shot timer, which will trigger all of the effects for about 1/4 second, and then turn them off even if the trigger (switch) is held closed.
The Laser diode, Red LEDs (muzzle flash), and the sound effect module, and the blue LED chaser are all turned on by transistors that are triggered by the timer.
The LED chaser effect consists of another timer set up as a normal oscillator, which is driving a 4017 decade counter chip. The decade counter lights up each of the 10 LEDs in succession.
You can see the effects in action in this video:
Step 2: Build the 555 Ic One-shot Timer
The timer that controls the effects is based on the good old 555 timer chip. I used the low-power CMOS version.
You can adjust the amount of time that the timer stays on by varying the values of the resistor to pin 7, and the capacitor to pin 6.
Time (seconds) = 1.1 x R x C
It is a good idea to set up the circuit on a breadboard to get the bugs worked out prior to soldering. However, in my experience, things can behave differently once they are reassembled onto a circuit board. I had to adjust my component values a little bit once i built the circuit on perf board.
Image courtesy of Rob Paisley.
Step 3: Add Some Output Transistors
Once i had the one-shot timer working, I rebuilt it on a piece of perf board.
I tried driving both the bright red muzzle flash LEDs and the Laser diode directly from the output pin of the 555 chip, but it didn't seem to work once I added the second effect, so I chained together 3 NPN switching transistors (with diodes to the trigger legs) to use as outputs for the effects. Using the transistors to turn on the effects individually gave much more stable results.
At this point you should set up the LED, laser, and sound module on a breadboard and test to see that they are being triggered properly.
Step 4: Build the LED Chaser Effect
I found this 10 LED chaser circuit on the web, and integrated into my design.
This circuit produces the sequentially flashing line of blue LEDs that shoot down the sides of the blaster when it is fired.
The circuit consists of another 555 chip, this time wired as a straight oscillator. The oscillator output drives the 4017 decade counter chip, which has 10 transistor outputs.
I wired up 2 arrays of 10 LEDs, one for each side of the gun, and hooked them to the appropriate pins on the 4017. I built the chaser effect on a second circuit board because I ran out of space on the first one.
I ran a jumper from the output of the first timer circuit to the LED chaser board where I had installed an NPN transistor to turn on the effect.
The chaser will cycle over and over while the signal is high, so I adjusted rate of the oscillator (variable resistor on pin 6-7 on the 555 chip) so that the chaser would do one full cycle during the time that the effect was in effect.
As you start wiring this stuff together, be sure to keep the final enclosure in mind, my gun was pretty jam-packed with wires when I was done. I could have planned a little better. It might have been worth doing a printed circuit board for this project.
Step 5: Prepare the LED's
The LED's that I used for the main emitter are ridiculously bright, and their narrow viewing angle and large 10mm package makes them project really far. I used 3 of them clustered together and focused at the same spot. In order to fit them into the barrel of my blaster, I had to grind down the cases and crowd them together a bit.
The 2 sets of 10 blue LEDs that make up the chaser effect, (which I call the pulse generator) have their anodes connected to a common ground via individual current limiting resistors. Pairs of the cathodes (left and right side effects) are wired to the output pins of the 4017 chip.
Now, as bright as the big red LED's are, I wanted to be able to shoot a visible blast of red onto a wall across a well lit room, so I added a laser. I ordered a laser diode that included a focusable collimating lens. The lens allows you to change the focus of the beam so that rather that shooting out a little pin point laser, you can adjust it to whatever size spot you want. I made it about 10 inches across at 30ft.
Step 6: Sound Effects
I purchased a Radio Shack recordable sound module to use for the blaster sound effect. I originally started to use a little child's toy sound recorder, but found that the memory was volatile, and the sound would be lost whenever power was cut to the module. The radio shack module uses non-volatile memory.
I cut off the microphone and wired the leads to the sound output jack of my computer. By pressing the record button on the module and the play button on the computer at the same time, I was able to load the sound onto the module.
Step 7: Build the Blaster
Of course, you could use these effects in any number of raygun projects, but I chose to build an LED Star Wars Rebel Trooper Blaster pistol because, well, "Hokey religions and ancient weapons are no match for a good blaster at your side, kid."
The Original Star Wars props were based on old Sterling sub-machine guns. Like the originals, my blaster is largely a model of a Sterling SMG with a few additions, such as the aluminum emitter and the scope.
I built my Blaster from PVC, aluminum tubing, scrap aluminum bits, sheet aluminum, wood, and miscellaneous bits and doodads that I had lying around. If you choose to build a Star Wars blaster, there are templates available that will help you with the lalyout. I used the template linked to at the top of this page on the Blaster Builder's Club forum to make the reciever tube, trigger guard, and magazine housing.
The emitter is aluminum tubing with aluminum trim. The cone tip is made from a wooden furniture leg from Home Depot. To aluminize the cone, I epoxied an aluminum skin to the outside.
The handle is wood, and is glued and screwed in place. I made a trigger that hits a momentary switch when pulled, which trigggers the electronic effects. I installed a power switch in the handle as well.
The grip is from an actual Sterling SMG. There are resin copies of the grip out there, but I found that the real ones were cheaper, and they don't shatter when you drop them.
The sight is a cheap red dot gun sight that I bought n ebay. I made a mounting rail from aluminum.
I painted everything but the emitter with a few coats of semi-flat black. There are some neat prop metalizing paint tricks that you can do with the finish as well.
Step 8: Stuff the Blaster
Once you have wired up your electronics and built yourself a raygun, you need to install the electronics in the gun. I glued a thin strip of wood to each blue LED array to make them easier to install.
I put the 4 AAA battery pack in the magazine housing, and made a little cap for it that looks like the end of a magazine.
The Speaker that came with the Radio Shack Sound Module was a perfect fit inside the PVC endcap. I drilled sound holes in the end of the cap.
Once you get the circuitry in place, you can solder up the connections to the effects and stuff the remaining wiring where ever you can fit it.
Step 9: Blast Away!
Here is a video of the blaster operating in a well lit room.