Introduction: A Cheap Laser Tag

About: It from bit

Christmas Holiday is one of the most awaited holidays in the

year. We have loads of DIY projects on internet which you can make during Christmas holidays

So inspired by one such project of MAKE magazine I decided to build a simple circuit for a laser tag game

There are at present loads of projects on internet regarding laser tag but this circuit is unique and can be built in a few pennies .Though it doesn’t have a score maintaining and other features but it presents us an opportunity to built a cheap circuit which can serve the basic feature of a laser tag

Step 1: Materials Needed

1) NPN Transistor (2N3904) x2

2) LDR x1

3) LED x1

4) 3v battery and holder x1

5) PCB x1

6) Potentiometer 50k or 10k x1

7) Wire

If you don’t have a potentiometer then you can use resistor from 1k to 10k but I prefer you to use a potentiometer


  • Solder iron and wire
  • Laser
  • Wire Stripper

Step 2: Understanding the Circuit

One of the most important things is to understand that how does this circuit work or else it would be just like copying and pasting some matter from website without using BRAINS to understantd how it works

So I am going to explain you the concept via a video and written matter

Written matter is separated in 2 parts

  1. Understanding the circuit
  2. Understanding the logic or brain due to which this circuit works

Now I will directly start with the explanation of the laser tag circuit and for all those who don't know you can check these sites


view the above video

So in the circuit we have a LDR ,a resistor and 2 Transistors

Now look at the circuit as I explain

  • When Light Hits LDR At sufficient level
    1. Current flows through the battery to the joint of LDR and LED
    2. The current flowing through LDR gets little but reduce as More light means Less resistance for the LDR
    3. But then also base lead of transistor receives less current than the amount flowing through the collector lead of transistor so the current flows through the junction of base and collector
    4. Now at the junction of base and emitter current again flows as there is no current at the emitter
    5. But then this will supply the current to the base of 2 transistor but again as compared to the current coming to the collector it is more than the current at the base of 2 transistor so current flows and the circuit subsequently get complete
  • When light doesn't hit the LDR
    1. Now in this case the LDR would give high resistance and its such that the base of the 1st transistor doesn't get the needed current and thus the connection wont be able to complete
    2. Now due to incomplete current flowing through the 1st transistor it further makes the second transistor OFF or due to not getting any current at base transistor is unable to make the circuit complete
  • Now you might be thinking that why do we have the other resistor so its basically to support theory that current always finds the path with low resistance in other words the current will floe through the part of the circuit that has the least resistance so now you know that why do we have this resistor as we cant change the value of LDR to get it work well in problematic situation like there may be high light in one room and low light in other room
  • So by just decreasing or increasing resistance of the resistor you can get desirable result I hope that you are so far with we
  • So this is how this circuit works so lets have recap
    1. When light falls on LDR its Glows the LED
    2. When there is darkness it makes the LED dim


Now get ready to know the main concept which made this project a success

SO as in the earlier part we studied that we light hits the LDR , LDR make the LED glow or in other words starts light so thus again that LED light which was started by some other light source glows and give light to the LDR and this process continues again and again making LED glow till some obstruction is there b/w the LED and LDR or the 2nd resistor values change(the resistor other than LDR) to such extend that the circuit circuit stops and thus the light of LED

Now enough of talking gather up you tools and parts and get ready to make one for yourself

Step 4: Placment of the Parts # MOC

  • First place all the components on PCB following the circuit which is given in the fritzing image


You can etch your PCB board I have given the fritzing image

Here are some tips for how to place components efficiently
i) The 2 transistor can be placed such that the collector of 1st transistor and collector of 2nd transistor are at adjacent holes of PCB and the emitter of 1st transistor should be adjacent to base of 2nd transistor

ii) Now try to place other components similar to the images given

iii) Remember not to cut the extra leads of resistor and LED it will be useful for you at time of soldering

iv) Remember to place LDR and LED facing opposite to each other this is what that will make this circuit work

  • Now cut the PCB but remember to leave some place if you would require it at time of soldering

#MOC is Making of circuit :-P

Step 5: Soldering #MOC

Now you have to solder the parts remember not to get your components damaged

Here are some useful tips

1. Keep the iron tip clean. A clean iron tip means better heat conduction and a better joint. Use a wet sponge to clean the tip between joints. Keep the tip well tinned.

2. Solder small parts first. Solder resistors, jumper leads, diodes and any other small parts before you solder larger parts like capacitors and transistors. This makes assembly much easier.

3. Use adequate ventilation. Most soldering fluxes should not be breathed in. Avoid breathing the smoke created and make sure that the area you are working in has adequate airflow to prevent buildup of noxious fumes.

4. Before use, a new soldering tip, or one that is very dirty, must be tinned. "Tinning" is the process of coating a soldering tip with a thin coat of solder. This aids in heat transfer between the tip and the component you are soldering, and also gives the solder a base from which to flow from.


Step 6: Testing Time #MOC

Now first test it by putting 3v battery in holder

Now adjust the value of potentiometer such that the LED gets just off .

Now point the laser to it LDR and see the result>>>>>>>>>>LED should get on.

Take help from my video this also shows how to turn off the LED using 2 techniques

Congo on creating your first Laser Tag At a low cost don’t forget to post the pictures of it will surely help others to make it.

Step 7: Finishing Up #MOC

Now all you have to do is to make it attach to the cloth Images will help you through this step i found that the little space which i left was helpful for me at this step

Step 8: PLAY TIME !!!!!

Kudos !!!!!!!! You did a great job now all you have to do is enjoy the result of your hard work make some more of them and play with your friend .

Take a look at the fight of me and my friend actually its just me shooting but i had a great time with it and check out the critic comments too

Step 9: Future Plans

You can further modify it using a 555 timer circuit in

different modes for the laser

Astable mode

This would help you to make Laser a machine gun style just click the button and the laser pointer will on and off I have made this circuit like that way So here are some images of it and the circuit to guide you

Monostable mode

This would be help full when you want to give the person just one chance to shoot the target usually I used it for making a shot gun in which you have just a fixed no of chances in India we usually during fairs or MELA for that you would be need to make a 555 timer circuit in Monostable mode

In the circuit just connect the laser pointer to the output and the ground make sure that you connect it with the same polarity.

So if you have any question regarding the circuit or explanatory part just post the comment Enjoyyy and forget to like my Youtube videos.

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