DIY Laser Tag System (Revamped)





Introduction: DIY Laser Tag System (Revamped)

   Here's one of those classic games you probably played with your friends as a kid at birthday parties, mock-up military training, or just hanging out with your buds. You probably play this with your friends still, but it's a pain to keeping paying to get only a few minutes of shoot-em-up fun. Why not build your own system and play whenever you feel like it? Well, this instructable will show you how to create your very own system, from simple to arcade-style complexity. I do not recommend this project to those without some of the supplies listed in the next step, because it tends to get very expensive fast if you don't have the stuff (don't worry if you have some of these, most are pretty cheap to buy at Radioshack). To those who don't the money or supplies, I suggest buying the kids laser tag systems you can find in Toys R Us for about $20-$30. However if you have the hankering for learning circuitry, have spare time and friends you don't know what to do with, or if you just wanna build something, this is for you!

Step 1: Price and Supplies

I'm a big fan of cheap stuff so I liked what I saw when I tried designing my own laser tag system and found I had most of the parts I needed to mimic an arcade-style system, though the more complex I got with the designs (for example designing a Who-Hit-Me display) the more expensive they became, but my simple design is sufficient and is fairly cheap to replicate (for multiple players). Below is a list of prices and supplies you're need (unless it says 'opt.' which shows which parts are optional) to complete your own laser tag suit. Parts listed as being optional are things you don't absolutely need to make the system shown in my photos (though you can get even simpler without the buzzer). The following prices (and supplies) are based off local Radioshack prices:
(opt.) x2 $.48 8 pin IC socket
(opt.) $.99 14 pin IC socket
(opt.) $1.99 perf board (these 1.99-cheapies should have enough holes)
$1.99 piezo speaker (some higher dB speakers are more costly)
$1.49 .01 microfarad cap
$.99 10k ohm resistors (5-pack)
$.99 65k ohm resistors (5-pack)
$.99 100 ohm resistors (5-pack)
$2.99 CdS photoresistors (5-pack)
$3.99 5mm tactile switch
(opt.) $3.99 SPDT toggle switch
(opt.) $1.49 trimmer resistor
(opt.) $3.99 pager motor ("rumble" motor)
(opt.) $2.99 breadboard
$2.99 assorted LEDs (20 pack - cost effective if you want to make more suits)
$1.69 LM555 timer chip (8-pin)
$3.69 (@ Walmart) Laser pointer or bright flashlight (sensitivity will be explained in the build and explanation sections)
Wires and/or alligator clips, 9v battery clip
9v battery

If you have ABSOLUTELY NONE of these parts these are the costs (not including batteries and wire).
(simple: $19.80+tax)

If you have recovered from that price induced heart attack, remember it's only if you're missing everything, it goes down significantly if you have most of everything.

Step 2: Let's Build It! Part1: the First Chip

OK, you've accepted the challenge and fun of making it yourself, now we'll go through step by step to guide you to creating this rather simple circuit. You can check your work by looking at the photos below and verifying they're in correctly. There will also be a schematic following the build photos for you to go off of if you can understand the pictures.

Step 1: Adding the heart and powering it.
In order for the circuit to work you'll of course need something to run your LEDs and Piezospeaker, but what fun is it to just apply power to them? Not very fun really, so we're using two LM555 timer chips to give our LEDs and speaker some style. Noting the clocking mark on the chips (denoted by a small dot or indentation) we hook up our first 555 timers' 8th pin to the power rail (the red colored column) and the 1st pin to ground using a jumper cable.

Step 2: Setting your trigger switch and reset threshold.
This laser tag system is actually comprised of two different 555 timer circuits. The main triggering circuit is called a bistable multivibrator or flip-flop circuit. The second triggered by the flip-flop activates a classic astable multivibrator to generate a tone. These are explained more in the next instructable step, so if you're not interested just skip over it. Now we'll set our "light switch" and reset button by first attaching a 10k ohm (10,000 ohms) resistor from power to your trigger pin (pin 2) on your first IC chip and a 65k ohm resistor from power to the reset pin (pin 4) on your first IC chip. Finally for this step we add the CdS cells (photoresistors) to the trigger pin (pin 2) in series (NOT PARALLEL!) directly to pin 6.
  And... while we're on the topic of photoresistors, you may know that there are also many different sizes of photoresistors out there which each have different values in different light levels. The ones I used were 1/4" cells with 4 "ribs" (what I tend to call the wave-like line running through the center of the cell). In ambient light they create 3.35k ohms each (3,350 ohms) of resistance, 2.5M ohms (2,500,000 ohms) of resistance in total darkness, and 330 ohms of resistance when hit with the laser light. There are three other sizes I examined in CdS cells each with a different set of values (given in the order: Darkness, ambient light, laser light):
1/4" cell with 3 ribs: 2.5M ohm, 3.35k ohm, 330 ohm (our photoresistor being used)
1/8" cell with 4 ribs: 3M ohm, 5.38k ohm, 600 ohm
3/16" cell with 4 ribs: 1.4M ohm, 2k ohm, 400 ohm
3/32" cell with 3 ribs:   (>= 10M) ohm, 4.2k ohm, 300 ohm

Step 3: Finishing our switches.
In the last step we had left off before we had actually finished the reset and trigger hookups. I did this because I wanted to keep the board relatively clean before we got in the way of our fun stuff and end up having a plate of spaghetti for a circuit board. Before we do the final jumper placements we must first add our light by taking it and connecting it from the output pin (pin 3) on the first IC to the ground rail (blue rail). Now we can add our tactile switch (push button) to our board. Connect your tactile switch to the reset pin (pin 4), using a jumper, and the other side of the switch to pin 6.

Step 3: Let's Build It! Part 2: the Second Chip

There aren't too many things you need to do in this step but I'll put them in smaller sub-steps so you it's easier to check your work if something doesn't seem right.

Step 1. Connect a 65K resistor from power to pin 7.

Step 2. Connect a 65K resistor from pin 7 to pin 2.

Step 3. Connect a jumper wire from pin 2 to pin 6.

Step 4. Connect a .01 microfarad capacitor from pin 2 to ground.

Step 5. Connect piezoelectric buzzer to pin 3 with a jumper wire and connect the buzzers ground to ground with a jumper wire.

You have now completed the tone generating setup. Congrats!

Step 4: How This Circuit Works

   This is that section some of you might be waiting for, the explanation. How does this work you ask? Surprisingly it's very easy to explain. There are two parts to this circuit we've built: a bistable multivibrator - also called a flip-flop - and the alerting circuit, an astable multivirbator putting out a square wave tone. In the circuit we built our tone is determined by the two 65k ohm resistors and .01 microfarad capacitor. You might wonder what these do to the circuit, which is explained by a simple *gulp* math equation. Ah, don't worry it's really easy with a calculator. The equation is: F(frequency)= (1/(.693(R1 +2R2)C1))1,000,000. (C1 is in microfarads) In short the resistors choose your initial frequency and tone and the capacitor multiplies/divides the outcome for the output depending on how small or large their values are (respectively). As a final example we'll analyze our own tone circuit with this equation, 1/ (.693((65000) + 2((65000)))*(.01))*1,000,000 = approx. 740 Hz or .74 kHz.
    Whew, that's quite easy once you see it in action more. This is how we get our alerting tone when we hit the mark, but how does it turn on and off when you hit the trigger? The output of the first 555 timer chip controls the power for the second chip. When the no light hits the target, the chip sits in a reset/off position and does not put out a voltage that the second chip can work off. When the target is hit, however, the voltage produced at pin 3 is about 3 volts, so the other chip can now work off of that voltage . Now that it can work, the tone is generated by the resistors and capacitor.

    The first chip is set up as a Schmitt Trigger that changes it's state depending on whether the Threshold is high or low. The threshold is set at pin 6 by a 1/3:2/3 signal by either the reset pin or the trigger pin (respectively) caused by variances in resistance (with our photoresistor) or by switch (with our reset button). A current that is 2/3 of the original source current must be applied to pin 2 for the chip to set a threshold in a high state while a 1/3 source current must be applied to the reset pin for the threshold to be set to a low state. In either case, the threshold state is kept until the opposing condition is met, which explains why the chip keeps the LED on or off over a length of time.

   If you really want to learn more about the 555 time chip I suggest borrowing Electronics for Dummies from a library or buying it in a bookstore and turning to chapter 7. (photos below are the circuit posted on page 161 and 164 in Electronics for Dummies.)

Step 5: New Step - the Laser Gun Circuit

You may have already noticed that this instructable is lacking one thing that really makes this a laser tag system: the laser cannon! Yes, as stumping as it was I finally have an idea of what to do with that clunky laser level freebie, gut it and give the laser new life. Though it isn't encased in an enclosure for portability the following steps will show you how to wire it up, you can either stay tuned for my update with enclosures and semi-advanced controls or take my circuit and go build your own enclosed ray gun, laser cannon, or laser rifle. Your brain is the key to having the most fun with this instructable. If you're ready let's move to the next step. There you will find a supply list, pictures, videos, schematics and written instructions for making your ray gun. Here we go!

Step 6: The Supplies and Some Explinations

Here's what you will need for your very own flashing ray gun circuit; short and sweet (with Radioshack prices included):

$1.29 - 100 mircofarad capacitor
$1.19 - 1 microfarad capcaitor
$0.99 (5-pack) - 100 ohm resistor (Color bands: brown, black, brown)
$0.99 (5-pack) - 470 ohm resistor (Color bands: yellow, purple, black)
$0.99 (5-pack) - 10k ohm (10,000 ohms) resistor (Color bands: brown, black, orange)
$0.99 (5-pack) - 22k ohm (22,000 ohms) resistor (Color bands: red, red, orange)
$0.79 (each) x2 NPN transistors (The ones I used were Radioshack 2N4401's)
($30+ dollars at Radioshack, find one at a cheap dollar store) Laser light
$1.49 - Light Emitting Diode (LED)
9v battery

A few things you should know before you tear your hair out over not having the supplies. There are quite a few things you can change about. One thing you can change would be the 2N4401 NPN transistors. To my understanding of the circuit you can use any NPN transistors (3904, 2222, 4401, etc.)  as long as they are NPN . If they aren't you may burn something out or it just plain won't work (As a tip to those who don't know if their transistors are NPN or PNP, simple use this circuit with two LEDs and your transistors in question. If the LEDs flash the transistors are NPN. If you end up using two PNP transistors the circuit won't work and there shouldn't be a risk of burning out the components.)
Another thing you should know is that you don't really need the LED in the circuit but it (A) shows if your circuit is hooked up correctly and (B) could be used for cool lighting effects on your ray gun. You may not have all the necessary resistances either but before you hit your head on the desk at the lack of parts you can simply use the power of tens to exchange the equation (Sorry, I don't know the math for this circuit...yet) but if you use a 100k ohm (100,000 ohms) resistor you may want to use a .1 microfarad capacitor (explained later on in the build).

Step 7: The Shortest Part: Building

I kid you not this circuit is really easy to build, though it can get pretty messy if not thought through before placing. Alright build time!

Starting off the board we plug in our two NPN transistors (on most if not all NPN transistors reading the pins left to right, flat side facing you, the pinouts are Emitter, Base, and Collector.) into the board.
Then you take your 100 ohm resistor and plug it from power to a random open place in your board which will later be bridged with your laser circuit (trust me, it's better for the sake of anti-spaghetti-plateness). We then take our LED and connect its anode (positive side) directly to power and its cathode (negative end) to a spot on the board. Immediately after that, place a 470 ohm resistor from the cathode to the Collector (With flat side facing you: the farthest right pin) of one of the transistors (just for my own preference, I used the right side transistor), this is what we'll eventually be doing to the laser light. Next, place our 100 mircofarad capacitor so that the anode (positive end) connects to the collector of transistor with the LED connected and the cathode (negative end) will connect with the base of the other transistor. We then reverse this process with the 1 microfarad capacitor by attaching its anode to the collector of the no-LED transistor and the cathode to the LED-transistor's base . Now that the most complicated part (yes, that was the most complicated part) is over we take our 10k ohm (10,000 ohm) and connect it to power and the base of the no-LED transistor and then connect a 22k ohm (22,000 ohm) resistor to power and the base of the LED-transistor. Semi-finally connect the emitters (the only pins you haven't touched) to ground using jumper wires. Now, finally, we take our beloved laser light and plug that puppy between the 100 ohm resistor and the collector of the formerly no-LED transistor. To give the circuit power we make a connection from the positive end of the 9v battery and the N.O. terminal (that's normally open when you're talking about switches) and connect the common ground (the lonely pin at the bottom) to the power rail on the board and finally connect the ground rail to the negative terminal of the battery and you're all set.

Step 8: How the Ray Gun Works

You're probably wondering how it flashes without a 555 timer chip. In a sense there is a 555 timer chip there but it's not what you would think of as one. You're actually looking at part of the internal mechanisms of the integrated chip we know as the 555. These transistors are like two little kids who normally boss other electronic components around, pushing them in the mud, taking their lunch money or rather electrons, and the like. However, when two of these bossy components are hooked up for the task of lighting an LED they each have have their own opinion of which LED should turn on and so they, like two kids playing tug-of-war over a toy, tug the current around both getting their own short time with a lit LED before the other pulls the power to their side and so on (till the battery does at least). The on time, off time, and brightness are all determined by the resistors (respectively) placed at the base with capacitors, the volume of the capacitors, and the value of the resistor in series with the lights. If you're still confused stay tuned for the more scientific explanation of this circuit works and how to determine the timings with calculations.

If you're interested post your creations for other Instructable-ites to view and have fun! Stay tuned for the enclosed version of the system.



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    I completed the curcuit but the led doesnt light up on pin 3.. instead it lights in pin 4 and pin 2.. also the circuit doesnt responds to an external lazer light ..

    hi I am trying to laser tag but I don't know how to start

    Hi I'm attempting to create something similar also using a decade counter to create a scoring/lives system, is it necessary for me to use NPNs between different parts of my circuitry to get enough power for each part? (Eg laser, 555 timer circuit and decade counter system) and could you use a 3 point switch to make different setting in different lights?
    Love the instruct able btw :)

    Sorry if I'm missing something, but why is there two different circuits? Is one for the laser gun and the other for.... could someone please help.

    Are the triggering circuit and buzzer circuit two separate circuits? also, where is the laser connected? I don't see it in the schematic. And the buzzer buzzes when the laser hits it, correct? And is there any way to temporarily disable the whole system (Trigger and Buzzer) for X amount of seconds after being hit?


    Add a monostable 555 circuit between the triggering circuit and the buzzer circuit. The triggering circuit triggers the monostable which produces one pulse when triggered. The length of the pulse is determined by your resistor and capacitor values the output pulse can activate your buzzer for the desired amount of time. Go here and check out monostable mode

    Does anyone know how to make the buzzer go off for only a second?

    I still don't know 100% how Laser tag guns work in the first place. I do know not all of them are rated for outdoor use.

    I am an Airsoft enthusiast, but the problem with both Paintball, and Airsoft is that the guns can only shoot a 50-75yrds with any accuracy, and they hurt too! I'm not a baby about it, and an ACU or hunting jacket works well at cushioning and blending in fine. But outside CQB, field games get kinda stupid. If you need an example of physics making fools of us airsoft geeks: a guy bought an Airsoft SR. Looks really cool, even has a bolt like a real Sniper Rifle: but it is only can shoot as far as the BB can fly at 500FPS. (Which is the max for any legal Airsoft gun) and even within those constraints, most public events won't allow a gun over 400 FPS. He bought a $500 bolt action gun, that can't shoot any farther than my $100 plastic AEG.

    I looked at the Laser tag guns on the market, for costumer use, and the best I could find where either $30 kids toys or $2k military grade training equipment.

    I figure, if I can learn how these things work, I could just try to convert one of my old broken Airsoft guns into a laser tag rifle. I looked into radio Waves, but they are too large to be focused into a "laser" but all the nerds I asked in regard to this subjects always go on about applications such as Space Telescopes and neutron colliders. I just want a toy gun that can shoot farther than I could throw a rock... and not kill my buddy in the process.

    is there an alternative for limit switch..??

    um just wondering cause this might be obviouse but im just getting started :P but if i wanted to have multiple PRs would i just have to connect them to the same circuit or build multiple ones? and if i can have just one circuit do i have to hook them up in series or paralel?