Garbloom:
Can someone confirm this as a possibility?
You're proposing to use the speed of light to measure distances of the order of yards? It strikes me as being utterly and completely infeasible to DIY; your only hope would IMO be to use a commercial 'laser distance measurer' but they are not cheap, and introduce the dangers of people looking into lasers.
not to mention that the speed of light is nearly 300 million meters per second. so 1 millisecond precision is 300km precision and 1 microsecond is 300m. Those numbers are in a vacuum and it does slow down slightly through air... but consider that it takes roughly 2.5 seconds to bounce a laser to the moon and back. Throw in the crazy precision that would be required when sync'ing the clocks of multiple sensors and it becomes a pretty infeasible task.
It is, of course, possible to use light speed to measure distance but there are much simpler ways 
I concur that measuring distance with the proposed method will not work.
An idea which I had is the following, which might give you the desired effect:
Instead of firing 1 packet, fire several, each with a different damage coefficient. Now send each of the packets with a different current through your led. The higher the current, the longer the reach.
Current can be controlled through a DAC-controlled mosfet, in between closed and open the mosfet has a part where it opens slowly as a function of voltage.
Another way to achieve this is to connect several resistors to your IR led, each chosen to give the desired current, and use transistors to switch to the preferred resistor.
Trial and error will learn the reach of each resistor setup. Then you will have to program you code on the receiving end so if it receives multiple correct packets from the same player in a short amount of time, only the highest damage coefficient will be used.
Voila.
Now: my tagger runs at 600 rpm fine, this works at the receiving end as well. I am not sure whether 1800 rpm (3 shot packets per shot) is feasible, but you would have to try. My taggers are btw standard equipped with 300 RPM, so 600 RPM will be rapid fire.
Cheers
Jack
hello everybody, this is a topic also very close to my heart and one I have had some experience in. With location tracking consider that GPS wont work indoors which is where a lot of the Laser Tag games would be played from.
also http://www.lasertagparts.com/arduino.htm is a good place to start
You could try making a self-tracker with accelerometer, gyroscope and digital compass.
Or you could put a grid of IR leds in the ceiling so that each led shines on a 2 or 3 meter circle on the floor. And that led would be beaming location ID over and over. 1 IR reader in every hat and your hat knows where it is if it points up and a transmitter is above.
I have also been working on a laser tag game very sporadically over the last couple years, mostly trying to figure out what I want it to be. I burned out a laser pointer, but did find some 5v laser modules on ebay that work perfectly with arduino , and they only cost me about $1 at the time I bought them. I've been modulating the signal at 38khz using Ken Shiriff's library for testing so far, and have found that an tsop4838 ir detector works with the laser. I have also got xbee's I'm hoping to integrate for real time scoring as well as tft screens that will give information on who last hit you, who you hit, your health meter, score, and ultimately, if you could figure out the location thing, have a dot showing relative position of friendlies and enemies like some video games. I like the idea of the ir leds in the ceiling for tracking, this could all be communicated through the xbee to the scoring computer or to the other players gear when hit in the laser stream. It's just a matter of how much info you want to send on the beam. Thanks for listening to my rambling, I'll be following this thread to see what comes of it.
I know it's a long time since the last post on this thread but perhaps DerekD will see this and tell me what sort of laser he was using with the TSOP4838?
Or (of course) anyone else that has used a laser with the TSOP4838?
...R
GPS does work inside nearly as well as outside. Depending on the roof material. But it will still be off by 10-20m.
A very expensive RFID grid would probably get appx 2 meter circles, with overlap you could place someone within 1 meter when they show up on 2 sensors. You just have to figure what it's worth and who will pay.
I resurrected this thread to get information about a laser that was used with a TSOP4838.
Clearly it hasn't worked so I will start a new thread.
...R
Sorry Robin, I'm not in the forum that often. The laser modules are used are like these.
http://www.ebay.com/itm/5pcs-New-650nm-6mm-5V-5mW-mini-Laser-Dot-Diode-Module-Head-WL-Red-/251363781672?pt=LH_DefaultDomain_0&hash=item3a8672ec28
The ones I bought are probably the same thing, the important thing is that they were 5v. My ebay history shows that the ones I used are 650nm and 5mW just like these. Now as far as using the sensor, the laser has to hit the sensor directly for it to work. Which is great if you want your hits to be very precise, but that could also be frustrating. I've tried using a table tennis ball to transfer the laser pulses to the sensor to widen the sensor area. the laser will light up the ball, but the sensor doesn't read it. It may be positioning of the Tsop in the ball or it may need some sort of amplifier, I'm not sure. I'm not working on this project at the moment, so hopefully someone else can help it along. I anyone figures how to make a larger sensor area, please post it for all. Thanks.
Please reconsider your decision to use actual LASERs.
http://www.polyphoto.com/tutorials/LaserTag/NoRealLasers.html
Biggest problem with LEDs there is collimation. IMO they should be sending IRDA and the receiver should have to get a complete message to register a hit, the target would record who hit it where.
Telescopes focus collimated light, the kind with the mirror at the bottom has a long focus. A tag gun could be made from a reflecting telescope with a tight angle CREE LED at the focus aimed back at the mirror.
Yeah it will leave a LED-size black dot in the center out of size of the telescope mirror wide beam. Oh well.
If your 'gun' shines on a 3" to 8" circle, would that be a bad thing? It would solve the pinpoint sensors problem by having a beam width. If you had enough sensors, you could track the spread of the hit and better find hit center and maybe alert the wearer of wounds and make loud sounds when 'wounded' body parts are moved.
I suspect the Laser Tag people have long abandoned this Thread.
@polymorph, rest assured I have no intention of pointing a laser at a person - only at model trains. I'm afraid of the lasers at supermarket checkouts.
@GoForSmoke, I don't know who your post is intended for, but I don't understand it in my context of using a laser and a TSOP4838 to control a model train.
...R
Robin2, I think you've confused your threads. This thread -is- about Laser Tag and pointing things at people.
Location tracking is not the easiest part, most gps are not accurate enough, but for rough distance it will be your best bet I guess. You will have to communicate this over any type of wireless network between the arduinos. Points of interest:
I have some lasertag software which handles full duplex IR communication, sound and display. The core eats about 50 % of cpu time, the rest is available for running the game.
I would not opt for a fixed system, you might want to play somewhere else.
polymorph:
Robin2, I think you've confused your threads. This thread -is- about Laser Tag and pointing things at people.
Thanks @Polymorph.
If you look back you will see that I resurrected this Thread when it was long dead in order to get information from @DerekD - which I now have. I started my other Thread when I didn't get information here (before Derek replied).
Consequently I wasn't sure if people were following up my enquiry here or the original Thread topic.
This is my last involvement on this Thread.
...R
If something on your train gear has a reflective surface you can still find out why not to use lasers.