Laser Gun Mods for LaserShot

 I just got a chance to test out a new laserShot system recently but was disappointed to find my laser guns mostly don't work with it. 

On power up I can hear clicking and in the software you can hit "switch IR filter" so it has a filter that blocks all but NIR light.  This explains why only some of my 780nm guns work with it.   I had a LaserLyte LT-TTL  I had ripped out the laser from and swapped it with a 780 a while ago and this one worked best.   all my other laser guns just went on when i pulled the trigger hitting the button behind the trigger and they stayed on however long the trigger was pulled.  So, since i cannot target  20-80ms that precisely... time to engineer it!. 

First attempt was to make a simple cap discharge circuit.   Putting a large'ish cap (400-600uF) in series with a discharge resistor across the cap of about 50-100 ohm  you get an RC time constant of about 50mS  (500uF * 100ohm).   this also  for a 3 V (2x1.5V)  supply gives just enough current to turn the laser on.  However I got better reliability when I switched to 3x  1.5 = 4.5V by series'ing 3 AG13 batteries.  Which happens to be what LaserLyte uses.  Duh.    The laser will stay on after the initial pulse but its so weak the camera ignores it due to the low current   4.5V/100ohm=4.5mA continuous and peak... something more.  It works but not great.   I put a 100ohm Potentiometer across the resistor and can tune it a bit but its a balance of lower Resistance increases "off" continuous intensity after the pulse while also decreasing reseat time to discharge the cap for the next shot.  Have it too high and the cap wont charge enough for a rapid double tap pulse.   Its not great but it works.  You just have to tweak the software a bit for detection threshold. 

So I then wanted a better engineer solution.  I looked up a few debounce, and push-button to controlled pulse circuits and settled on a low power BJT circuit that can be dropped in series if needed but performs better if its a little more integrated into the components.   See diagram below.  You definitely want 4.5V powering this or the drop over the BJT can be problematic.  But this circuit is nice because it lets you fine tune pulse width and gives a fairly constant intensity on high pulse before the cap saturates and the BJT switches back to high impedance.  Its a good thing these cheap VP9 spring airsofts only cost about 20 dollars =).

--Upper left:  The basic circuit from which the others are derived based on restrictions or desired performance.   
--Bottom left,  Using a single MOMON pushbutton (trigger) activates the laser for the time constant of the RC pair.  It only powers on when the button is hit and powers off as soon as the button is released or after the RC times out on the BJT.    
--Bottom Middle,  Depending on the existing wiring and supply it may not be reasonable to source the diode over the BJT so instead we sink it.  Again behavior is as above but it doesnt shut off completely due to leakage through a resistor but leakage is low enough the camera doesnt pick it up for shot detection.  This one will kill batteries a little faster over time if you dont give it a power switch on the supply, especially tinny lithiums.

--Bottom Right,  Playing with a design for a pulse circuit that even if the button is released before the 50ms or whatever is up, it will stay active until the first cap discharges sufficiently.  I need to play with this design a bit more to see if it works well enough or is stupid. 

The bottom left and middle designs both work well enough for laser shot, you just need a bit of tuning depending on your laser and detection setup.  

After playing  a bit longer Ill provide a review of laserShot vs  Smokeless Vs Point blank simulator.  Hint.  more camera drama.