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The Official High-Speed Camera Thread

All non-spudgun related discussion goes here such as projects, theories, serious questions, etc. All "off-topic" posts (aka useless posting, determined by moderators) will be removed.
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Unread postAuthor: Technician1002 » Fri Jul 29, 2011 1:58 pm

I found a bridge rectifier is not needed. Software debouncing provides unwanted delay. Automatic gain control is your enemy. A good preamp with fully manual gain control will do wonders. Set the ambient sound level at about 10% of the required trip level and the amplitude of the event will provide a reliable trigger with no delay due to debouncing. With the correct microphone polarity, the pressure wave front from the discharge can provide the required offset in the correct direction to trigger logic.

Below is an example of the mouse Musket discharge. The gain is too high and the peak is clipped. Note the polarity of the air discharge wavefront is negative. Reduction of the gain and reversal of the polarity will provide a nice high amplitude positive output for the pressure wave front from the cannon. The ambient noise prior to the shot is low level. The rising noise level prior to the shot is the pilot opening, a 1/4 inch ball valve.
Image

Edit, a 339 Quad Comparator can make a easy to adjust trigger level detector to interface between the analog world and the digital world. A pot can be used to set the trigger voltage and it can take care of inverted analog signals by swapping the inverting and non inverting inputs. They are inexpensive and work well.
http://www.national.com/mpf/LM/LM339.html#Overview
I've used them for differential thermostats to turn on and off pumps for a solar collector. Panel warmer than the tank, pump on. Panel cooler than the tank, pump off.
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Unread postAuthor: ramses » Fri Jul 29, 2011 4:14 pm

Well for this, you wouldn't use that type of software debouncing. I would just hook up the mic to a hardware interrupt (normally bad thing) or a polling while() loop and have the ISP/code after while loop handle the programmed delay (if necessary). It could then then delay for a bit longer (500 ms?) after triggering to prevent a subsequent trigger.
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Unread postAuthor: Technician1002 » Fri Jul 29, 2011 7:05 pm

If you add a 500ms delay to my cannons you would miss the shot entirely as it is often completed in 20ms.

For example, expand and check the time line of the audio posted above.
The hiss starts at about 34.910 seconds in my recording and ends in the clip shown at 35.010 seconds for the event time of about 20ms. 500ms later is pretty much room echoes and reverberation as the recording is of an indoor shot.

At about 500FPS for many average shots, you would need the camera about 250 feet downrange to spot the projectile. :D
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Unread postAuthor: ramses » Fri Jul 29, 2011 9:13 pm

Technician1002 wrote:If you add a 500ms delay to my cannons you would miss the shot entirely as it is often completed in 20ms.

For example, expand and check the time line of the audio posted above.
The hiss starts at about 34.910 seconds in my recording and ends in the clip shown at 35.010 seconds for the event time of about 20ms. 500ms later is pretty much room echoes and reverberation as the recording is of an indoor shot.

At about 500FPS for many average shots, you would need the camera about 250 feet downrange to spot the projectile. :D


500ms AFTER the flash fired. So hear the clunk, ignore all clunks for the next whatever delay (down to about 4 us), trigger the flash, wait 500ms for all the clunking to stop, done.
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Unread postAuthor: jackssmirkingrevenge » Fri Aug 12, 2011 2:17 pm

Not going to publish this particular protoype but here's a couple of test shots in case you were wondering my lathe was idle ;)

[youtube]http://www.youtube.com/watch?v=hQWJvKSBpVU[/youtube]

[youtube]http://www.youtube.com/watch?v=DpT0osFEYM8[/youtube]
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Unread postAuthor: LeMaudit » Fri Aug 12, 2011 3:19 pm

hahaha... kill Playmobil KILL KILL!!!!

Sparkling!! 8)
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I HAZ A BANG!
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Unread postAuthor: jackssmirkingrevenge » Fri Aug 12, 2011 3:24 pm

The recovered "corpse" was actually quite amusing :D
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Unread postAuthor: mattyzip77 » Fri Aug 12, 2011 4:02 pm

Talk about a DIRECT HIT!!!!!!! Lol!!!!!!!
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Go Bruins!!!!
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Unread postAuthor: jackssmirkingrevenge » Tue Aug 16, 2011 3:25 am

Something from the firearm blog, not as innovative as the maker claims but interesting nonetheless:

[youtube]http://www.youtube.com/watch?v=_eUlpPY96Ok[/youtube]
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Unread postAuthor: saefroch » Tue Aug 16, 2011 12:04 pm

Somebody should shoot a small-bore hybrid or high-pressure pneumatic underwater to compare...
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Unread postAuthor: ramses » Tue Aug 16, 2011 4:02 pm

saefroch wrote:Somebody should shoot a small-bore hybrid or high-pressure pneumatic underwater to compare...


I would, but I sold my EX-F1...
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Unread postAuthor: jackssmirkingrevenge » Thu Aug 18, 2011 5:39 am

ramses wrote:I would, but I sold my EX-F1...


I would, but I don't have an aquarium.

Remins me of this joke :D

A conversation in a bar:

"Logician? What's that?"
"Okay, I will explain it to you: Do you have an aquarium?" – "Yes ..."
"Then you certainly have some fish in it!" – "Yes ..."
"And as you have an aquarium with fish in it, you certainly like animals." – "Yes ..."
"And as you like animals, you certainly like children." – "Yep ..."
"And as you like children, you certainly have some." – "Yep ..."
"And as you have children, you certainly have a wife." – "Yes ..."
"And as you have a wife, you certainly love women." – "Yeah ..."
"And as you love women, you do not love men!" – "Of course!"
"And as you do not love men, you are not gay!" – "Right!"

The mathematician leaves, and a friend of his "erudite student" turns up:

"Imagine that: I've just met a logician!" – "A what?"
"A logician. I will explain it to you: Do you have an aquarium?" – "No ..."
"Queer!"


But I can make hybrid buckshots yay!

[youtube]http://www.youtube.com/watch?v=Xh7IgK-DA34[/youtube]
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Unread postAuthor: ramses » Thu Aug 18, 2011 1:26 pm

[quote="jackssmirkingrevenge"}
Remins me of this joke :D

A conversation in a bar:

"Logician? What's that?"
"Okay, I will explain it to you: Do you have an aquarium?" – "Yes ..."
"Then you certainly have some fish in it!" – "Yes ..."
"And as you have an aquarium with fish in it, you certainly like animals." – "Yes ..."
"And as you like animals, you certainly like children." – "Yep ..."
"And as you like children, you certainly have some." – "Yep ..."
"And as you have children, you certainly have a wife." – "Yes ..."
"And as you have a wife, you certainly love women." – "Yeah ..."
"And as you love women, you do not love men!" – "Of course!"
"And as you do not love men, you are not gay!" – "Right!"

The mathematician leaves, and a friend of his "erudite student" turns up:

"Imagine that: I've just met a logician!" – "A what?"
"A logician. I will explain it to you: Do you have an aquarium?" – "No ..."
"Queer!"

[/quote]

Only a fool would assume that the inverse of a statement is automatically true. :D :D
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Unread postAuthor: Hotwired » Tue Aug 23, 2011 12:11 pm

Playing with the old 30KV.

[youtube]http://www.youtube.com/watch?v=1ydr_iE2ccU[/youtube]

Note electrical interference with mouse.
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Unread postAuthor: Hotwired » Wed Aug 31, 2011 10:01 pm

Igniting an overloaded open chamber:

[youtube]http://www.youtube.com/watch?v=2MOMGN7uBE8[/youtube]

Even if it wasn't at 240fps you could see the blue cloud of flame crawling down the chamber.

There's not enough air for it all to burn to start off with but the initial combustion blows out a load of fuel to mix and burn outside the chamber and draws in more air for the rest of the fuel to burn inside the chamber.

Since the fuel at the bottom has to wait for oxygen and for the turbulence from the flames above to mix it, the flame front slowly crawls down mixing in air with fuel and burning as it goes.

That's my theory on it anyway :D
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Last edited by Hotwired on Thu Sep 01, 2011 3:57 am, edited 1 time in total.
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