I am trying to create a trigger for a high speed flash using an Arduino, a Sharp BS120 photodiode, and a laser pointer.

The results i've obtained so far are inconsistent, the system seems to miss small objects passing straight through the laser beam and also seems to have a significant delay, several millimetres worth of falling before the flash triggers.

Also, it seems to be insensitive to soap bubbles, which is what I need to trigger off.

Can anyone suggest a suitable circuit for this application.

  • 2
    \$\begingroup\$ Please post your current code and schematic. \$\endgroup\$ – geometrikal Jan 17 '14 at 1:30
  • \$\begingroup\$ Have you considered triggering by reflection of the laser off a soap bubble, rather than by interruption of the beam?If you can see through the bubble, the laser will pass through it. Similarly if you can see reflections on the bubble surface, the laser will reflect off it. \$\endgroup\$ – Anindo Ghosh Jan 17 '14 at 3:37

Well it sounds like enough energy from your laser is going straight through the bubbles and hitting your photodiode.

Try to ramp down the power on the laser, or put it through some sort of darkening filter such that it barely doesn't trigger when there's nothing in the way. Once that is sorted out, we can look at the timing problem. I suspect it has more to do with too much energy from the laser than anything else.

  • \$\begingroup\$ Thank you all, after a bit of tinkering I traced the issue to my programming. Removing the serial output solved my problems. Thank you for your help and suggestions. Hope to some day be able to return the favour. \$\endgroup\$ – user35670 Jan 17 '14 at 18:41

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