adjustable optic triggering / Electromagnetic Projectile Accelerators / Forums

Forums

4hv.org :: Forums :: Electromagnetic Projectile Accelerators

« Previous topic | Next topic »

adjustable optic triggering

previous 1 2

Move Thread

LAN_403

Benj

Fri Aug 19 2011, 04:11PM

Registered Member #4050 Joined: Sun Aug 07 2011, 04:06PM
Location: France
Posts: 17

Sounds like a great idea! Next step is to test it for real

i have no idea why half of my sceenshoot is white...

NE555 output is Red , trigger voltage is blue

PSCG

Sat Aug 20 2011, 10:04AM

Registered Member #3792 Joined: Sun Mar 27 2011, 06:07PM
Location:
Posts: 136

...Using an only 555? well, how would you delay the pulse then?...

Sorry Benj. It was a premature thought

...just one thing: I'm not an expert ( far from it ), i'm a real begginer in optical triggering and "serious" coilguns.

Nor i'm an expert in coilguns. I've only built 2 very simple coilguns before i start with my coilgun rifle project (a very difficult project - 1+ year effort and still haven't finish it).

I think that the second sim that you've made fits better my problem with delays. If you make the real life test please let us know about the results.

Benj

Sat Aug 20 2011, 11:01AM

Registered Member #4050 Joined: Sun Aug 07 2011, 04:06PM
Location: France
Posts: 17

That was forty's idea, not mine

. I'll try this.

i'm also trying to build my own and first coilgun rifle. Still a long way away.

Forty

Sat Aug 20 2011, 05:53PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

if i have the time, i'll breadboard this up later after running some numbers for c and r values. it sure would be nice if it does work with such simple parts.
with regard to the microcontroller, i don't have a pic programmer, my arduino is too big, and i hate programming. unless i used a pic to run a whole bunch of other features in the gun, it would be a big waste of space with all the external components (c's, r's, crystal, voltage regulator, etc) that it would require. but most importantly, i'm not good with circuit design, so i'm using this as a learning experience and it's already going quite well (actually opened my electronics textbook)
i now know how to make my own jk or d-type flip flop or even a 555 timer from logic gates and comparators.

Slid

Tue Aug 30 2011, 09:21AM

Registered Member #853 Joined: Thu Jun 21 2007, 03:08PM
Location:
Posts: 14

When I made my gun, It triggered the coil not when the lightbeam was broken, but when it came on again. I did this to have the projectile well inside the coil. I uses a 4017 counter, which has a schmitt-trigger on the counter input. This was connected to a simple resistor/photodiode setup. I then got the trigger-signal on output 1

Forty

Tue Aug 30 2011, 03:36PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

I want to be able to adjust when the coil fires. it's a pain to find the right initial distance from the coil for the projectile. even when you do, if there's an injector stage or full stage before it, then that location is no longer correct because the projectile will have an initial velocity. so with a built in delay in the triggering, i should be able to just turn a trimpot until the velocity is maximized.
coincidentally, I just started a photography course at school, so i may try some high speed shots using the same circuit. it will be weird to actually build a camera flash for once, i'm so used to taking them apart. gives me an excuse to build a boost converter too.

Artikbot

Mon Sept 05 2011, 12:12AM

Registered Member #3247 Joined: Mon Sept 27 2010, 09:42AM
Location: Spain
Posts: 137

I defend the photo gate trigger right before the coil.

Automatic fire, no further circuitry needed, if you do it with photodiodes it will be so damn faster you can stick the sensors right at the entrance of the coil.

Why complicating stuff with timers and delays? Sure it is very very tunable, but it is also way more prone to errors, and needs very extensive tuning periods until you achieve maximum performance, while the optical barrier mode simply works from the very beginning.

Forty

Tue Sept 06 2011, 03:20PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

but if it just so happens that the projectile initial position "sweet spot" isn't right in front of the coil, then the gun will suck. with a little bit of math and the right components, i can just change the initial position from outside the gun by turning a trimpot (1 turn = ~1mm).
if i want to play with different sized cap banks or different projectiles without building a new gun and coil every time, then the addition of a 555 or two into the circuit seems like a good idea.
if/when i make a gun with a lot of stages, the design can easily be extended to accommodate them

previous 1 2

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob