Spring 2016 3DOT Goliath Laser vs. IR LED Trade-Off Study
By: Kevin Moran (Electronics and Control Engineer), Tae Lee ( Systems Engineer)
Our team’s mission is to decide the better approach for a game of laser tag, either by using lasers and light detecting sensors, or by using IR Receivers and LEDs. From the research we concluded on proceeding to test Photo-resistors and lasers for our game of game tag. The reason being that the laser has a longer range to activate the resistor, over 14 meters more than the IR that was tested. The laser can hit targets further, because the light emitted is concentrated on a single focus and wavelength (for the most part) and then transmitted. The IR LED diffuses its wavelength, sending it in all directions. In order to achieve this game using IR receivers, the range will have to be too short and the IR LED must be able to concentrate its light on the target. The laser requires less operating voltage than the IR receiver, and that is an advantage since we are trying to keep our current dissipation to a minimum.
The laser and photo-resistor were tested using an Arduino circuit, and the Plot function in order to observe its behavior in the presence of the laser and of natural light.
Laser test results:
When testing the laser and its receiver, it was necessary to ensure the photo-resistor would not activate under normal light conditions. When a laser light was not focused on the target, the graph showed a flat line very close to the zero value. When the laser was aimed, the graph peaked. It was noted that the peaks increased if the laser was aimed for a longer amount of time. 1 second provided us with the taller peaks in the graph. This analog signal we are obtaining must be converted to Digital in order for receiver to activate regardless of the amount of time the laser aims to it.
Recommendation:
If the laser is to be powered the 3DoT board, this board must be able to supply the 40 mA that the laser requires. When tested with and Arduino, it was noted that this board only provided an output of 20 mA. I recommend to either use a smaller laser that requires less than 20 mA to operate, or to build a PCB with a circuit regulator in order to ensure the laser works as it is intended.
Sources:
http://www.plaintree.com/pdf/DataSheets/Plaintree’s%20LED%20vs%20LaserNEW.pdf
http://www.farhop.com/product/farhop-5-volt-5mw-650nm-red-dot-laser-diode-module-5-pieces/
http://www.digikey.com/product-detail/en/350-00009/350-00009-ND/1774434