Hi folks, I am planning to build a simple laser tag game that consits of a laser gun and some pop up targets.
The Gun
The laser gun would be a simple, 3d-printed gun-style case with a laser emitter in it and maybe a vibration module and a beeper. If a trigger is pressed, all components (emitter, vibrator and beeper) should work for, say 250ms. That's all it has to do I guess.
The Targets
There would be 6-8 pop up targets, simple cardboard disks. Each one would have a servo that randomly pops up that target. There is a photoresistor in the center of each target that detects a laser hit.
I am not concerned about the coding but I never worked with lasers and photoresistors so I am not sure what parts would me most suitable for this project. Here is my list so far:
1. Which one of the above photo sensors would be most suitable for this?
The LM393 has a poti that allows for a customizable sensitivity if I am correct, whilst the laser sensor module is small sized (but has a fixed sensitivity?). Or just using simple photoresistors? But with what resistance and what kind of additional resistors then? The photo sensors should easily detect a laser hit, also when the game is played in a well-lit room.
2. Would I need to use an Arduino for the laser gun?
All the gun had to do is to let all parts run for 250ms or so when a trigger is pressed, then power itself off again. Are there any kind of buttons out there that would allow me to do so without the need to use a microcontroller (power on by button and power off again after a certain amount of milliseconds)? Would the vibration motor start vibrating as soon as it receives power from the battery or would I need a microcontroller to activate it?
Of the three sensors, the "laser sensor module" is the only one of any value.
To implement this, the laser must be modulated at a high frequency - commonly 38 kHz but you can use others.
The photoresistors are not capable of discerning such a high frequency, so are not useful.
Since you want to gun only to "fire" for a limited burst - 200 ms sounds reasonable - when triggered each time and it must modulate the laser and you want it to produce sound effects and you probably want a "magazine limit" function as well, a microcontroller sounds like a good choice.
It will be very difficult to hit a commonly sized light receiver with a laser beam from more than 20cm. With a 250ms pulse you even won't see where exactly the beam ends up. Get a couple of those cheap laser pointer modules and find out yourself how wide the spot will be at your intended distance. These modules can be driven directly by any 5V Arduino, eventually a resistor can reduce the brightness. Then you can play around with various carrier frequencies and burst times. Photo resistors can be bigger and easier to hit than phototransistors, but only by unmodulated or quite low frequency beams - again find out yourself.
The "Laser sensor module" the OP links does not appear to use a modulated beam signal. I may be misreading the ad copy on the sales page.
I have a toy IR blaster, it has a few lenses in it but makes too broad a beam to be used for target practice.
So maybe think about lenses on the gun and the targets while you also consider using a modulated beam, which at the very least will help greatly with ambient light problems.
alto777:
The "Laser sensor module" the OP links does not appear to use a modulated beam signal. I may be misreading the ad copy on the sales page.
I didn't think it did. You can use the Arduino to demodulate, perhaps using a lower modulation frequency in the hundreds of hertz range. The 38 kHz sensors are designed for IR.
alto777:
So maybe think about lenses on the gun and the targets while you also consider using a modulated beam, which at the very least will help greatly with ambient light problems.
The problem is of course, that the laser beam is far too narrow, while you need lenses to focus a non-laser beam.
It may actually be more practical to use a lensed 38 kHz IR beam (you calibrate it using a camera which can "see" the IR) to actually detect the "hit" in addition to a visible laser only to give a visual aiming indication.
Optical systems work both ways! Check out the May 1970 issue of Popular Electronics, which I am sure you all have carefully stored in the basement. Cough. Or google it.
A laser beam can be injected into the eyepiece of a monocular, for example, and the detector placed at the eyepiece of another. Adjustments will allow forming a beam of whatever divergence you require.
So some kind of lenses will get you over the narrow beam thing.
A parallel plain laser beam could be added, but you'll only see the beam if there's stuff in the air. Although green lasers seem to see a crap-ton more of that stuff. Are they just more powerful? I am frankly afraid of a small green laser pointer I bought at a going-out-of-business sale at Radio Shavk. A sad day BTW.
For feedback, something on the target that lights up when hit.
TheMemberFormerlyKnownAsAWOL:
No, it's just that your eyes are most sensitive to green light.
I think that particles show up better in green light as well - the reason the sky is blue! In which case they would also show up well in a blue laser beam but the eye is not as sensitive to blue light.
Which is in turn why blue LEDs such as in "Christmas Lights" and recent computer models are very decorative (and used because blue and white LEDs - which are fluorescent - are the most recent and so considered "modern"), but comparatively ineffective.
alto777:
The "Laser sensor module" the OP links does not appear to use a modulated beam signal. I may be misreading the ad copy on the sales page.
Modulated light allows to amplify the low photo transistor/diode signal by an AC amplifier, suppressing all continuous light. Search for according op-amp circuits, eventually you'll find one with a converter from AC to a stable DC signal ready for a controller input. An audio level detector module may work as well, when you replace the microphone by the photo device.
Couple of comments:
Is this laser tag or a laser firing range? Sounds more like the latter. What is the anticipated range?
In my [limited] experience with cheap laser diodes, the beam divergence is highly variable from one unit to the next. Which means that two identically constructed guns may vary widely in the accuracy needed to score a hit. It may also mean no need for optical conditioning of the beam.
I don't think the nature of the laser diode is critical, but since they have a narrow spectral output, the detector should have its maximum sensitivity in this region. Read lots of datasheets!
Consider using an infrared pair. This will provide immunity from ambient lighting and will also simulate a real gun, in the sense that the point of impact can usually not be detected visually (unless at very close range with a large caliber).
S.
Those cheap 5V diodes (up from 10 pcs. 1.22€) have no adjustable focus. I'd think that adjustable focus is available only with more expensive and higher energy diodes, where modulation of the current source may be problematic.
a constant current driver with an input for TTL modulation is easy to make (but are also already available if 10KHz are enough) ... laser diodes, same as leds, works in current, so nneds constant current drivers ...
A common AIXIZ holder can be used if you use bare laser diodes (say, no already complete modules) if you know how to work safely with bare laser diodes, but can also find decent complete modules (this one just as example is a 50mW in an AIXIZ holder .... this other one have already inside a constant current driver with TTL modulation input) ... cheaper than anything that can be produced at home, also ...
beam can be expanded with a doublet (negative lens followed from positive lens), or more simply defocusing the original lens and adding a second positive one ... this cause larger beams have usually lower divergences (but in a targeting line it may be a disadvantage)
Photoresistors are not good, as said, too slow ... phototransistors are ok, photodiodes also better ... there are also large photodiodes, but their cost is absurd, better use a common BPW34 or similar ones, inside a small black tube with a lens in the front (photodiode in the focus of the lens), for have a more large area to hit ...
DrDiettrich:
Those cheap 5V diodes (up from 10 pcs. 1.22€) ...
Are almost all crap ... no real diode inside, just a bare laser chip soldered on a piece of PCB, poorly mounted in a slot ... no protection, no current limitation, no modulation, just a serie resistor ... good for play, not for build anything serious ...
I don’t know how I’d change things, but I am alarmed by the idea that anyone anywhere can just buy a 50mW laser module… and even as I type that I want to get one.
I don’t care so much if someone somewhere gets into trouble. I am more worried that that kid on my block will get tired of fireworks and smoke bombs and all the kind of fun that never killed any of us cough and move on to squirting laser beams all over the place. Double Y Yikes.
Like the crazy Ukrainians making a ray gun out of a magnetron taken from a microwave oven, OMG you almost hope something goes wrong and they learn a lesson. Instead we celebrate ingenuity, haha.
Certainly the OP means to be playing with relatively much lower power beams. Still plenty of reason to be cautious.
Well, ofcourse, lasers must always be used after turning brain on (:D) ... 50mW CW are enough for damage permanent the retina, but if you use it modulated (say, PWM 20% or similar), and use small bursts (200 or 300 mS), also a casual reflection in an eye does not transfer enough power density to damage it (ofcourse none must shoot a laser intentionally in the eye of anyone)
And for increased safety, can be used "laser goggles" (green ones for red lasers), also the cheap ones available on ebay works good enough for a similar use ... at the same time, "mirrored" sunglasses worth nothing as protection (optical density of a cheap laser goggle is usually at least 3, most of them 4, that means it left pass from 1/100 to 1/1000 of the blocked wavelenghts ... common sunglasses left pass usually from 30 to 50 % of light)
As any other tool, lasers can be dangerous if misused ... i worked years with a 2KW CO2 laser cutter without a single accident, and played with tons of laser modules, from 5mW to 1.5W, still without any accident ... just need to not misuse them
But i agree with you about stupid kids that can place their hands on potentially dangerous pointers ... some Chinese sellers still sell through internet to anyone 500mW "pointers" in green, and also 2.5W blue one, if one can pay the price ... and in the wrong hands, they ARE dangerous ...
I recall deciding against trying to build a CO2 laser featured in Scientific American, which may still have a section where amateur scientists could reveal their innovations…
Because I know myself and having a dangerously powerful and invisible beam would mean trouble sooner or later.
Kinda protective of my eyes and hands. And wishing lately I’d tried harder all my life to take better care of my brain, LOL.
Rotating the top part, probably ... but as i said, their quality is really bad ... see here for some pics ... the "diode" is simply a cheap, low quality bare die without any case, exposed to dust and contamination, with no active current limitation,and probably will last very short time ...
In decent modules you can find TO18 sealed diodes, mainly (only 250mW ones usually use "open-can" TO18 ones) ... also the Chinese one i linked before (the one with 3 wires) have probably inside a TO18 diode with an active current driver, always much better than these cheap 2/3mW toys ...
