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Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
I have tried to browse the old forms and use the "google" but i have only been able to fine his infact this is from my older project when i was first working with coil guns.
The issue i found with this circuit is it is inaccurate and doesn't seem to trigger the SCR sometimes (although when it does work its fast enough t fire the second stage)
Is there a better one i can use or a modification i can make to this existing circuit
Registered Member #11734
Joined: Thu Mar 21 2013, 08:44PM
Location: Brno Czech republic
Posts: 35
Hi, i use optogate with IR PIN photohodiode (Its much fastert han photo transistor) look at my scheme i think its simple Schmitt triger is there cause optogate its conected to logic
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059
I was looking at a variant of this to charge up airsoft pellets using UV and found that it wasn't feasible, however a beam break detector using a VCSEL is perfectly doable and costs less than £2 on ebay for the parts.
Registered Member #54278
Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367
ZakWolf, I see that you stated you have been in a lengthy search for a reliable triggering mechanism for coilgun stages. You didn't state the exact nature of the 'trouble', But here is a type I designed years ago to solve the problem due to EM 'coil interference'. It works by eliminating the need for ANY detectors, receivers, or wiring to be near the coils. Briefly, a hole is drilled where the projectile is to trigger the coil switch. The end of small length of optical fiber is placed in the hole and an electronic opto-detector is placed 'out of the way' on the other end of the fiber. The projectile is sharpened to a conical point (45 degree slope and shiny) on the rear end. Now, the optical source shines down the barrel (the safe end) With the projectile inserted, the light is blocked and can't travel down the barrel. As the end of the projectile passes the hole, the light striking the back of the projectile and reflecting from the 45 degree slant will squarely hit optical fiber, energizing the coil.
I had had good luck with this, but that was in the 1980's before LED's were super bright. So now I guess you could use a cool-looking color glow of your choice.
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Infrared trigger circuit
Schmitt triger is there cause optogate its conected to logic 
