SparkFun Forums

[dkulinski]

Hello fellow Sparkfun forum members!

I have long been lurking on this forum and just recently start to post on some other threads. One of the other people is interested in my lasertag project. So after a good nights sleep I have decided to post about it here.

Both my sons love lasertag. We have picked up the toy versions of these before but have always been disappointed about the capability to run outdoors in full sunlight. Range becomes extremely limited. Not to mention you are held down by the modes of the game the manufacturer has decided to incorporate. So as my very first embedded project I decided to make lasertag! I have not completed the game yet, I am still prototyping. This will be a good work log for me. Sometimes I will take a 2 or 3 month break, it helps me to avoid frustrations with repeated failures. Hopefully I am over that period and I can keep moving this forward. All comments are welcome.

First some good resources:
http://www.lasertagparts.com/mtdesign.htm
http://www.laserforums.com/forum/

These boards have helped me in my conquest for my original design. Through reading their posts I was able to determine parts. You will see that my prototypes are running off of 9v but later on that will change to a 7.2v NiMH.

Alright, now on to my design:

lasertag.jpg

This is by no means complete of the final design. I have learned that I need to drive the MOSFET by a transistor so I can make sure it is fully saturated and delivering max voltage to the IR LED. Most of these parts aren't from Sparkfun but I can assure you that they did start on a Sparkfun Arduino and move on from there.

Currently the 4 microbuttons are not connected. These are in place for when the LCD is finally attached. I am making a removable module for the LCD. This way I can have either a more graphical UI or I can just rely on the buzzer for input.

Once the code is completed and the circuit tested and revised I will be moving to a small PCB. I would like to make some small lasertag guns and some larger ones. All code is done in straight avr-gcc C code. I was running into problems with Arduino and timer usage. Now I am in total control! Once complete a git repository will be available.

Features that are in progress:

• Basic lasertag - 1 shot 1 kill
• Advanced lasertag - multiple gun modes with an ammunition counter
• Shooting gallery - Like the classic shooting galleries in old time arcades

Features that are planned

• Score keeping
• Multiplayer over 2 players
• Ref mode - Allows field programming of guns for different modes
• IR bootloader - Allow firmware updates over IR

Feel free to ask questions or make suggestions. I realize I am reinventing the wheel but this was done to increase both my electronics knowledge and my to experience just how different embedded programming is.

Dan

[Mee_n_Mac]

Are you primarily looking to add features and novel modes or trying to solve the outdoor sunlight problem ?

[dkulinski]

The first hurdle is overcoming the sunlight. To do this I have some Vishay TSAL600 IR LEDs and Vishay TSOP38338 IR decoders. This won't allow me to use the Sony based code that Milestag uses but I am fine with that.

After that it is all a matter of software.

Dan

[StaticDet5]

I've been looking at this since... since paintball became too expensive.

One of my technical hurdles is the projection optics. I know I want a focused beam at a distance, but I never got around to figuring it out.

I remember my optical physics class, and the ray diagrams. Translating that into real world specifications is where I must have fallen asleep...

I'm primarily interested in "rifle" style systems (Long barrel, more design room in the stock). It seems to me that a highly focused IR LED (I think I've found them as tight as 6 degrees) aimed at a 1.5" to 2" lens would work, but again, I haven't really looked at the physics. Do you have any thoughts on that? Are there issues with IR transparency in optical lenses?

I can't wait to see this project progress. It's another one of my "dream projects".

[dkulinski]

Actually there are lots and lots of folks that work on the optics. laserforums has a huge thread on optics. I'll get a picture up of my IR LED and lens. It is a simple copper tube with the LED at one end and the lens at the other. I am not using a 1.5" to 2" lens but I have yet to test the distance. Once of the hurdles is alignment of both the LED and the lens.

As for transparency, most of the time you can find out what glass is used and check on the IR characteristics (most allow all light to traverse). There are coated optics but again I don't believe these block IR transmission.

Luckily this system will easily allow you to swap out the LED and you can insert it into any type of focusing assembly you like. Heck, look up the LS 20/20 system. It uses an actual laser for firing and has been tested to be safe with the milestag system. Good luck getting that culminated!

Dan

[dkulinski]

StaticDet5, I just wanted to give you a link to the laser system I mentioned earlier:

http://www.lasersoftstore.com/

Dan

[Mee_n_Mac]

How "fat" is the beam at say ... 100 ft ? Does it cover a person, head to toe ? Or just particular body parts ?

[StaticDet5]

That's the question I had as well. I just scoured the LaserSoft site, and I can't believe we can't do it cheaper.

[dkulinski]

Actually less than 2 inches. Check out the target discrimination video.

Dan

[Mee_n_Mac]

Actually less than 2 inches. Check out the target discrimination video.
Dan

What do people wear for sensors ? By that I mean how many and where are they worn ? I assume the person isn't covered with a "senso-vest" and "senso-hat" such that any hit on what would be a vital area would be counted. Far away, where the beam has some width to it, you can count on a good aim hitting at least one sensor. Up close, with a small diameter beam, you really have to aim at the (presumably few) sensors to score a hit ... or have a lot of sensors ... or have the ability to "spoil" the beam. What would be scored a hit w/firearms or paintball or airsoft might just miss a sensor.

Or is it me that's missing something ? :doh:

[dkulinski]

Yes, in such a tight beam you are going to need to be very precise. usually sensor domes are made up of a few sensors wired in parallel. A head sensor usually has 4 IR sensors for 360 degree coverage. For right now I have a single sensor that I have tied to the front of my PVC mock up.

Dan

[StaticDet5]

Which brings me to my next question: beam scatter from the terrain/target.

How much scattering is there? Could I bounce the beam off of a wall (or tree) to get a "suppression hit"?

[dkulinski]

There are reflections. It really depends on the surface it hits. There are plenty of examples of indoor play where you get hit from behind due to a bounce off of a wall. Also, things like leaves are going to severely reduce the effectiveness of the beam. Anything that obscures the receiver will do this of course.

Dan

[StaticDet5]

I had a friend over the other day, and his big questions were about beam size and forming (Forget my project. He "hrmph'd" over it, and that was that).

He asked some real pointed questions (that I probably should have been able to answer, but I'm not real sure about the practical applications of the physics portion of this).

If you take an LED and lens assembly, set the lens so it projects the beam to an infinite focus (or near infinite focus, so that the beam converges at a range measured in kilometers), what's the limitation on the range? Particularly if you're encoding a digital signal on the beam? It seemed to me that this would largely be a "Signal to noise" issue.

So... How does the digital signal work? He and I started talking, and I got to "The Way I Would Do It", which has no real basis in reality.

I'd probably look at a "multi-level" signal.
The start of the beam would be a simple signal that says "You're hit".
The next part of the shot signal would indicate what actually hit you (This would allow for different gun types)
The next part of the shot signal would indicate who hit you (Personal Identifier information)
The final part of the signal would be an information section, conveying "other" (It would be "cool" to track who shot you and from where)

I pointed him to the different websites. He's balking at the cost, and now he wants me to get him a bargain basement cost for the beam-projector and sensor web. I told him he has to wait.

[dkulinski]

Alright, so you have to understand a couple of things here.

Beam coherency, this isn't going to be near as nice as you would want it to be. Lasers are the best coherent beam of light you can get. When designing a focuser you take an IR LED and find out the angle of half intensity. Right now mine is at 10 degrees. With that information I tried to find a lens of a certain focal length and size to concentrate that powerful IR beam. No matter what you aren't going to get the non-parallel beams to line up perfectly parallel out of that lens. What you are looking for is something like the following (excuse my poor mspaint skills):

led-lense.png

You want the lens diameter to be 2 * tan(theta) * the focal length. This will capture most of the energy of the LED. Still your beams are going to scatter and the energy will degrade over distance. Also, it is really hard to focus a beam you can't see!

The tricky part becomes mounting the LED in such a way that you can culminate the LED position with the lens. The larger the lens the easier it is to align and the better range you get. Of course after a certain size you get into the zone of ridiculousness.

As for pushing information. Well instead of making your own IR receiver, use a simple one on the market. Vishay makes a wide variety and seems to be a favorite. These things will automatically discriminate between signal and background interference. On top of the receiver I will be using a simple RC5 code to push 14 bits around. This will transmit damage and who hit you. Why don't I store the type of weapon that hit you? You can find that out after the fact when you combine all the data.

Dan