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Unread postPosted: Sun Jan 18, 2009 12:03 am
Author: Insomniac
starman wrote:WOww, those are beautiful!! A couple of those trimmed right would make awesome computer desktop wallpaper.

How again are you synchro-triggering your camera/spudder? What is the black you are using for your background?

EDIT: OK sorry I just reread your original post on the synchro-trigger. I would like to figure a way to trigger my digital camera to do this.


For this it is simply a long exposure (some digital cameras call it 'fireworks mode', although I did it manually on this camera) in the dark. I just wait for the timer to click down and hit the cannon's trigger.
You should really try it with your triple thunder launchers: Do a few with no burst disk, and a few with one and see how the flame expands when it leaves the gun. You may need to set your ISO higher for the burst-disk shot as they are typically much dimmer than a non burst disk shot. You will probably need to do it at night (rather than in a darkened room) I wouldn't envy being the one to fire a shot indoors with one of those. :shock:

The background is just a black towel draped over a chair.

As for making your camera trigger when you fire a cannon, there are a number of problems with that:

1. Most digital cameras have a 'shutter lag' long enough to make synchronisation difficult if you lack some sort of delay timer on the cannon.

2. As fast as shutter speeds are getting, most pics will still be blurred when trying to photograph such things as projectiles and explosions. Also, higher shutter speed means the camera needs either a higher ISO (much grainier pic) or huge amounts of light to let the sensor pick up a decent photo.

3. Unless you crack open your camera and rewire the shutter button to some wires so you can build your own little device to trigger both it and the cannon simultaniosly, there isn't usually a way to tell the camera to fire other than pressing the shutter button. (some cameras have an IR sensor for a remote, so you could exploit that)

These reasons are why strobe photography exists in the first place. Strobes trigger instantly, can last for extremely short durations, and it is easier to open up a strobe or use an external flash than to try and open up your camera. Photos such as THIS are pretty much always taken with strobes, as it is just so much easier than to try and use a fast shutter speed. Disadvantages are that any light in the picture (tracer round etc) will show up as leaving a trail because the shutter is open for a long time.

FishBoy wrote:very cool. how much did the sound trigger setup cost?


Around $20, although I have multiple parts for pretty much every component in case I screw up. I haven't built it yet, still waiting on the MOC3020.

Unread postPosted: Sun Jan 18, 2009 12:13 am
Author: starman
Insomniac wrote:For this it is simply a long exposure (some digital cameras call it 'fireworks mode', although I did it manually on this camera) in the dark. I just wait for the timer to click down and hit the cannon's trigger.
You should really try it with your triple thunder launchers: Do a few with no burst disk, and a few with one and see how the flame expands when it leaves the gun. You may need to set your ISO higher for the burst-disk shot as they are typically much dimmer than a non burst disk shot. You will probably need to do it at night (rather than in a darkened room) I wouldn't envy being the one to fire a shot indoors with one of those. :shock:


Thanks for the info. I really hadn't considered going to fireworks mode and just doing it manually. The remote fire capability can be put to good use there.

Don't worry, there will be no shooting of those things indoors...:shock:

Unread postPosted: Sun Jan 18, 2009 12:17 am
Author: Insomniac
Bah, thought of some additional info to write, and by the time I was done you had posted. Oh well, be sure to post any pics you take here. I wonder how the flames from your guns will compare to the little one I was using? Will it scale or will they be completely different? Hmm.

EDIT:

starman wrote:Don't worry, there will be no shooting of those things indoors...:shock:


Thats half a relief, and half a dissapointment. With no burst disk, my mini displaces enough air that when my doors are closed it makes my window rattle slighly. I wonder what would happen to the window if your three guns went of simultaniously?

EDIT EDIT: Speaking of long exposure photos, I actually took the photo that is my avatar. (sister waving around a sparkler for 15 seconds)

Unread postPosted: Sun Jan 18, 2009 1:29 am
Author: starman
Insomniac wrote:I wonder how the flames from your guns will compare to the little one I was using? Will it scale or will they be completely different? Hmm.


The flame that I can see (very short period of time) is usually about 2 ft long, mostly light blue and looks like a muscular 3" dia bar of flame. I would like to see some of them photo'd though.

As far as shooting without a burst disk, I've never tried that except with the potato or tennis ball barrel attached and not sure how well that will work. I suppose if I turn the fan off and fire very soon after fueling I might get something...or start out with the fan on and disk in and pull the disk at the last second. I haven't really considered "dumbing them down" like that before now.... 8)

Unread postPosted: Sun Jan 18, 2009 1:34 am
Author: Insomniac
Try it, it makes an interesting sound even on small scale. (a really deep, fairly quiet 'WHUMP' sound)

EDIT
When mine fires with a burst disk it is a very brief, dim flame. It is quite directional and doesn't seem to expand as much as the non-disk ones do.

EDIT EDIT: Just realised I have some footage of it firing with a burst disk. It is the last full-speed clip (not much to see in slow-mo)
The other clips are the same gun with cone attached to the lid so I could make special effects style explosions.

[youtube]http://www.youtube.com/watch?v=GxpBdL95-Yk[/youtube]

Bah, not this again. I used to be able to embed vids, what happened?

EDIT EDIT EDIT: Ah, that's better.

Unread postPosted: Fri Jan 23, 2009 6:48 am
Author: Insomniac
Ok, got the parts, but for some reason (messed up order?) I ended up with some MOC 3021's instead of MOC 3020's.

I had a look at the datasheet, and it would seem the only difference that the 'imput trigger current' is typically 8 instead of 15, and max of 15 instead of 30.

Will this part work in the circuit I'm using it for, or will it alter sensitivity, not work at all, or burn out?

EDIT: Just checked the catalouge of the place the shop ordered it from (for convenience we just asked the electronics store to order it for us), and the moc3020 and moc3021 are listed as the same product, so it would seem you can't specify which one you want. I guess that means they are pretty equivilent. :)

Unread postPosted: Fri Jan 23, 2009 1:55 pm
Author: jimmy101
Insomniac wrote:Ok, got the parts, but for some reason (messed up order?) I ended up with some MOC 3021's instead of MOC 3020's.

I had a look at the datasheet, and it would seem the only difference that the 'imput trigger current' is typically 8 instead of 15, and max of 15 instead of 30.

Will this part work in the circuit I'm using it for, or will it alter sensitivity, not work at all, or burn out?

I suspect you'll be OK. Did you post your circuit? If you have a trimmer potentiometer (vairable resistor) anywhere in the circuit then you should be able to get the correct trigger current.

Post you results and circuit... I'm interested in giving this a try :)

Unread postPosted: Fri Jan 23, 2009 4:52 pm
Author: rp181
I am planning to do this eventually, but with a optical triggering system to capture projectile in mid flight. Main use is coilgun, so sound wouldn't work too well.

Unread postPosted: Fri Jan 23, 2009 5:30 pm
Author: Ragnarok
rp181 wrote:Main use is coilgun, so sound wouldn't work too well.

Yeah, that would be a problem.
About the only noises mine give out are when they charge, and the mild click of the trigger switch.

Unread postPosted: Fri Jan 23, 2009 6:42 pm
Author: Insomniac
This is the circuit here: http://www.diyphotography.net/universal ... sh_trigger

This circuit doesn't have vairable sensitivity or anything, so if I wished to add that, what resistor should I replace with what pot?

I'll try it as-is to see if it fits my needs, and if it doesn't work then I'll have to experiment a bit.

Also I've skipped the optical part of the trigger because I woudn't use it.

Unread postPosted: Fri Jan 23, 2009 7:16 pm
Author: rp181
for sensitivity, the simple way is to just block the microphone with foam or something.

Unread postPosted: Fri Jan 23, 2009 7:44 pm
Author: Insomniac
What if I want to make it more sensative? A big paper cone perhaps? :D

Unread postPosted: Sat Jan 24, 2009 12:26 am
Author: Insomniac
Bah... just spent a couple of hours with dad wiring it up (going slowly so I didn't mess it up) and when I clap my hands or yell.... it sits there and does nothing. Bit annoyed, to say the least :( .

Will post back later with photos and the exact layout we used so that if we did somthing very stupid one of you can point it out to me. :lol:

EDIT: Heres some pics of the circuit, and the diagram we followed (we modified the exact layout so it would work better on the board, nothing important moved (or so we think)

In these pics the red and blue wire pair are for the power, the two blue ones with a white jack attached go to the mic, and the other two blue wires go to the flash.

Image

Image

Image

Sadly I don't know enough to find what is wrong... All the solder joins are pretty good and we checked each break we made with a meter, so I don't think it's anything like that.

Unread postPosted: Sat Jan 24, 2009 10:44 am
Author: rp181
Just take is step by step. Start with where the power eneters, and keep moving forward.

Check the polarity on everything.

Unread postPosted: Sat Jan 24, 2009 6:50 pm
Author: Insomniac
I checked the polarity of everything, checked the resistors (matched the colour codes with a spare and checked that with a multimeter), and we even shorted out the emittter and collector with a bit of wire (if I understand correctly, this is like switching the transistor fully 'on')

Nothing fires the flash, and I'm unsure of how else I can troubleshoot it. I don't have an osilloscope so I can't see exactly what is going on.