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).


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.