Apr 05

Laser Tag Update 4/5/15

My deliverables from two weeks ago were:
1. Rewrite the bill of materials for the tag unit
2. Purchase three additional units
3. (Optional): test tag distances with different protocol timing.

I sorta updated my bill of materials. I have purchased most things from mouser.com, so I have a record of everything that I've purchased and will be able to purchase more if I need to.
I have now purchased materials to build four additional units. Why four? That will give me enough materials to have 5 units. So I could have some asymmetric game play (4v1, 3v2, etc.) or just have up to five people test the things. Or one will break. Who knows.

Do Next:
It will take a week or so for the parts to ship to me, and in the meantime I should prepare for the first game. The only next step I can think of is:
1. Build a receiver unit. It should be able to receive tags from a wide angle (360 degrees is nice, but not necessary). It should have an indicator LED on it.
2. Adjust the code for the first game played.
I am trying to build the minimum viable product. That means the minimum that I can do to make this work is what I should do.

For the first part, I basically need an array of IR receivers that are looking in different directions for a tag. I'm planning on using around 8 right now, because each of the ones that I'm using has a 45 degree field of vision. With 8, I get 360 degrees. I will have to mount that on the tag unit so that you can be tagged from any direction.
I should put an indicator LED on this part. This should go on top of the lens tube. In fact, I could build this in two parts so that you could still see down the center of the tube in order to aim.

For the second part, I need to make the code react to getting tagged in some way so that I can play a game with it. What is the most basic game that I want to play? Standard death match. Each player can get hit a certain number of times. They are out after hit a certain number of times. I need to add some code to keep track of the number of times someone has been hit, and if that counter reaches 0, they are out (I could have the indicator LED stay on or something.
If I want to make the game last for a certain amount of time, I could use a timer on my phone.

For future work, I can get stuff laser cut here:
http://www.cherrylaser.com/
http://www.lasersoverlosangeles.com/

Mar 09

Laser tag update 3/8/15

I missed last week's update, but I still worked on the laser tag project. I just didn't post. Well, here's to make up for lost time:

My deliverables from last week were:

1. Change IR LED current to 1 Ampere. Done.
2. Get distance tests for 1 A with 4.5" lens and a 1" lens. Not done.

So, I did upgrade the board a bit. I was using a solderless breadboard for my prototyping, but it was difficult to hold the darn thing together while aiming at my receiver board. Since I need to make a prototype anyway, I built a version on perfboard that had a breadboard layout on it. That way, my prototype would be sturdy enough that I could walk around with it and test it. I changed the current draw up to about 1 Amp as well. I am not using the 4.5" lens, and instead am using a 3.49" lens that is a standalone lens (the 4.5" lens is encased).

Specifications:

Voltage for LED: 5 V
Resistance for LED: Seven (x7) 33 Ohm resistors in parallel, resulting in 4.7 Ohm total resistance.
Current for LED: 1.06 (max is 1A)
Lens Diameter: 3.49"
Lens Focal Length: 9.5" +/- 0.125"
Max Transmission distance: ?? (not tested)

The purpose of this prototype was to build a unit that could be carried around. I used cardboard as my building material, as it is easy to cut, I have a bunch of it after purchasing stuff, and I can build things with it really quickly. I don't care about making it look pretty at the moment. I just need to see if it will work.

This is the first laser tag prototype

This is the first laser tag prototype

I will do distance tests eventually. However, currently, I have my receiver (which is basically another tag unit) turn on an LED when it is tagged. However, I can't see the little LED very well when I am standing 90 feet away, so I'll need to hook up my laptop and walk away, tag the receiver, then walk back. I'll do it eventually. Not enough time these past two weeks.

Another fun fact about using a larger lens. I empirically found the focal length by focusing the light of the sun (which is as close to a collimated source as I can get. If you have a better solution than focusing your light on something 92 million miles away, please let me know). When I did that, I noticed that the spot is larger than the spot of light I got when using a smaller lens. This is beneficial because the LED is not a point source, but is 5 mm in diameter. Using a larger lens will allow the focal point to have a larger diameter, so I will be able to collimate more light.

I will also mention to check for floating inputs. I didn't solder on the receiver initially, as I was pressed for time. That meant that the input was left floating (I didn't turn on internal pull-up resistors, since originally, there was a receiver there). My tag unit would stop tagging for some reason. I thought it was a power supply issue, code issue, and eventually tracked down that I had a floating input. Oops. I soldered the receiver in, and everything worked fine. If I'd taken the time to solder that last bit on, I wouldn't have been frustrated with the unit upon building it. Let that be a lesson.

Eventually, this needs to be turned into a tag unit that I can run around with and send/receive tags. Here's a short list of work that I will need to do eventually:

1. Build an enclosure - should be done after prototype done
2. Look at multiple IR receivers - (simplest way may be to add multiple receivers to the unit. Current ones don't have 360 degree field of view)
3. Test using 1 resistor instead of 7.
4. Determine what connection you want between your LED and tag unit. (maybe for the final unit, you have a red LED next to the IR)
5. Build multiple devices and test them in the field!

Future work (after first game):

1. Add LCD
2. Add RGB LED?
3. Add 58 kHz receiver for other types of tags
4. Make different lens combinations with different resistors on them with different tag rates

So, based on those things, I should probably test adding multiple IR receivers to my project and make it work with multiple receivers as my next step.

Next Steps:

1. Test multiple receivers. I have a few extra, so I shouldn't have to buy any more to do these tests.

Feb 15

Laser Tag Update 2/15/15

So, about two years ago, I wanted to make a course to teach laser tag. I didn't make it a habit, and it didn't get done.

Now, I've made some progress towards that laser tag. However, like the me of the past, this is still a large project, and I haven't gotten very far.

So now, I'm going to (try to) use some of the advice I've got from Extra Credits. They make videos about video games, and their advice can be translated to other projects. I'm specifically talking about their series on making video games, and their rules video. I should refer to this every once in a while when I am unsure of what to do.

Completed Work

1. Create a program to send and receive tags
2. Build a prototype that can send and receive tags
3. Build a lens setup and test adding a lens - adding lens increased tag distance
4. Build LED test setup and increase current - increasing drive current increases tag distance
(Note: requires batteries that can supply the current, and capacitors)

In Progress

1. Increase range of tag unit send/receive

Methods:

In my meanderings across the internet, books and the like, I have come across information on optics. I haven't done very much with optics, so this is a lot of trial and error on my part. However, I do know that I want to collimate light. Basically, I want to take light from an LED (emanating at about 25 degrees) and turn it into a beam that travels straight. Fortunately, if you buy a lens, they tell you the focal length, or distance away that a collimated light source will be focused. Put a light source that far away, and presto, instant collimated light.

However, what assumptions are they making about that light source? In the land of physics, everything is a point source, meaning it doesn't have any height or width. I tried using a 1" diameter lens to collimate a 5mm diameter IR LED. I got it to transmit about 50 feet, but it did not work very well outside. When I checked what the beam looked like with a red LED, the beam was not a column, but focused a few inches from the lens. If I want my lens to work more like the theoretical column, I need to make my LED look more like a point source. That means a larger lens or a smaller LED. Why not try both?

Deliverable:

1. Get a larger lens/lenses 2"+ in diameter.
2. Build test set up and test 2" diameter lens (inside and outside) and record transmission distances at standard currents

Future work

1. Add more light indication.
2. Make tag unit more sturdy.