The Official High-Speed Camera Thread

[evilvet]

I'm working on a version in my spare time using flash units from disposable cameras.

Not sure if you saw this http://www.spudfiles.com/forums/ideas-f ... 22917.html but lots of good info on flash guns herein.

Cheers

[Technician1002]

I was thinking more along the line of one of these.
http://html.alldatasheet.com/html-pdf/1 ... R2101.html

This 6 element package is what is typically used in a CD or DVD player. Finding a broken one will provide one at my favorite price. The small diodes are very fast. In a CD or DVD player the diode package is nicely mounted for you complete with a ribbon cable. Unsolder the socket for the cable from the electronics board and solder it to your project.

Word of warning. Those low capacatance items are ESD workstation stuff only. Careless handling will destroy them.

If you are interested, I can explain what all 6 diodes are used for in a CD player.

[evilvet]

The LDR tends to be a relatively high capacitance item so the response is somewhat slow.

Also, I am using a 10k resistor on the LDR to pull it low, I think I need to experiment with 1k or lower to increase the sensitivity of the voltage divider at high lux; I loose low light control but all I care about is "My God its full of stars" vs "anyone not wearing 2 million sunblock", hopefully that will be enough to capture the fast transit I want to use with full tank pressure.

[Technician1002]

Warning, the diode is very subject to ESD. Use proper ESD protection.
These are fast enough to read the pits on a spinning DVD.

As a bonus, the package includes a nice IR LASER light source. Properly positioned, it makes a very effective passing object detector.

[evilvet]

If you are interested, I can explain what all 6 diodes are used for in a CD player.

I would be most appreciative of a wisdom dispersal; that said my soldering skills and ESD/SMD capabilty are roughly equivalent to http://en.wikipedia.org/wiki/File:Homer ... Abbans.JPG
so be gentle

[Technician1002]

If you are interested, I can explain what all 6 diodes are used for in a CD player.

I would be most appreciative of a wisdom dispersal; that said my soldering skills and ESD/SMD capabilty are roughly equivalent to http://en.wikipedia.org/wiki/File:Homer ... Abbans.JPG
so be gentle

The four spots in the center are the main pickup and focus servo. The pairs cross corner from each other are mixed together. A cylinderical lens will make a round spot oval in one directon if focused too close and too far the other direction. The two pairs are compaired to provide the focus error signal and drive the lens focus coil to servo drive it into focus.

The two off center line spots are measuring the edge of the track of pits. As the beam starts to hit the edge, one diode gets a strong reflection while the other moves onto the row of pits. These two are for tracking and make a high speed line following robot out of the device. The high speed component drives the lens to track off center discs and the low frequency component drives the sled motor so the sled follows the row of pits from one end to the other. The tracking diodes are not used for signal detection. Only the center 4 are summed together to detect the signal endoded in the disc.

This page covers focus and tracking somewhat but does not go into the detals.
http://www.gadgetsguru.in/how/gadgets-w ... d&pageno=1

A service manual sometimes covers the cylindrical lens used for the focus servo and difraction grating used to create the three spots used for pickup. The center is for signal and focus and hits the 4 center diodes. The two side beams are skewed to the sides of the track and are used by the last two diodes for tracking.

Edit found a block diagram of the optical block including the difraction grating and astigmatic lens.

The center orientation of the 4 diodes is not important as long as it is properly oriented to the lens. The other pickup shown in a prior post shows the diodes oriented 45 degrees to this diagram.

[jackssmirkingrevenge]

Spotted on endo:

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[jackssmirkingrevenge]

[youtube][/youtube]

Needs moar pressure/lighter ammo load to make those paintballs burst but impressive visuals nonetheless.

[evilvet]

I'm taking another tack on this.
Despite Technician1002 best advice and in light of my inadequacies in getting the DVD hack to work, I am reverting to a cruder method.

I have been working on this most of today and can report:

My "canon" such as it is consists of a 1/4" solenoid valve and 300mm of brass tube. At 100psi it is perfectly adequate to put a sabot'ed 4" nail neatly through pretty much anything I stick in front of it, particularly at point blank range.

The good part of the plan is that the solenoid makes a good loud "clunk" in the microsecond range before the valve is open enough to expel the projectile.

To trip the flash I am using an electret microphone with a pre-amp based on this http://www.jaycar.com.au/productView.asp?ID=KC5166 which gives me a nice spike in the 50-80mV range when it hears the solenoid start to open.

Arduino code says "listen for clunk, wait x msec for the round to clear the barrel and put pin 13 high to fire the flash".

It actually works surprisingly well, valve goes clunck and flash goes "flash"

Next problem:

The output is a fairly jagged A/C wave form which is leading to some false triggers and hence multiple exposures. My thought was to use a bridge rectifier to get a DC full wave output and caps to filter it but the problem is that the diodes forward voltage is too high to actuate on the electret output, 0.7Vf against 50-80mv Vc.

Do I:
a} Go to the pub and forget the whole thing
b} Build a super diode using an op-amp
c} Use the spike output to trigger a 555 wired for debounce as the flash trigger
d} Do something clever with a trannie (Settle JSR, settle........)

BTW, amazing canon shot, M1A1 means never having to say you are sorry.

[jackssmirkingrevenge]

Can't the solenoid switch also start the sequence, without putting a microphone into the loop?

a} Go to the pub and forget the whole thing

Always a plan

d} Do something clever with a trannie (Settle JSR, settle........)

BTW, amazing canon shot, M1A1 means never having to say you are sorry.

Actually a T90

[Ragnarok]

Needs moar pressure/lighter ammo load to make those paintballs burst but impressive visuals nonetheless.

From my perspective, I'm more irritated by:
- Them taking their masks off
- The fact that it's somehow a repeater.

[evilvet]

Can't the solenoid switch also start the sequence, without putting a microphone into the loop?

Actually a T90

I guess the T90 caption might have given that away. Too busy watching Cadel hoist the flag for all of Oz when posting. Yah for Australia !!

Anyway, to return to the thread.

Yes I could wire it via the solenoid trigger but the problems of switch debounce are still going to be there since I am using a mechanical rather than electronic switch. I was also thinking of a generic high sensitivity sound trap to use in other photo capture applications where the solenoid may not be involved.

I am enrolled in an electronics course at my local college for the next few months so I might ask the lecturer his opinion and see where we go.

[ramses]

Do I:
a} Go to the pub and forget the whole thing
b} Build a super diode using an op-amp
c} Use the spike output to trigger a 555 wired for debounce as the flash trigger
d} Do something clever with a trannie (Settle JSR, settle........)
e} Use software debouncing

[evilvet]

@ramses
Thanks for that, I hadn't seen that one

I got it working with an op-amp to bring the signal up to 2.5Vdc then filtering it via a bridge rectifier to give me a nice clean DC spike for the Arduino.
If I dont freeze my butt off in the lab tonight I should have some photo results to show by Sunday night

[ramses]

@ramses
Thanks for that, I hadn't seen that one

I got it working with an op-amp to bring the signal up to 2.5Vdc then filtering it via a bridge rectifier to give me a nice clean DC spike for the Arduino.
If I dont freeze my butt off in the lab tonight I should have some photo results to show by Sunday night

All right, now I'm curious. How'd you manage to filter it with a bridge rectifier?