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Topic: Water & Sound & 24 Hz sine wave (Read 5575 times)previous topic - next topic

focalist

#1
Mar 14, 2013, 01:38 amLast Edit: Mar 14, 2013, 02:10 am by focalist Reason: 1
VERY cool...Okay.. but I believe the forward and reverse effects (as well the frozen motion) is because the frequency is the same as the frame rate, 24 HZ.  I would assume that similar effects would be obtained as long as the frame rate and the oscillation rates match.. or is there some magical resonance at 24 Hz?  For that matter, considering the sound level generated by a big ole speaker, maybe a solenoid could do much the same job in a much smaller space with much less power... or even a servo/stepper if the frequency of going back and forth is as low as 24 hz... I don't do much with servos, but I know that buzzing a stepper back and forth that fast could be done..

(edit- after thinking about it, 24Hz is subsonic)

Hmm.  Since I can do some neat frame rate stuff with the EOS and Magic Lantern, have a couple of old 6x9" car speakers and some tubing....

stoopkid

#2
Mar 14, 2013, 04:13 am
Yeah, the trick here is that the frequency matches the frame rate AND the shutter speed it very fast. You'd want to do this in the sun or with lots of light. In person, the water would not look like this. The speaker is only wiggling the hose, the camera gives it the still look.

If you did this with a regular North American camcorder you'd want 30Hz. You can do this with anything, even a ceiling fan would appear to do strange things if you filmed it at a high enough shutter speed.

http://en.wikipedia.org/wiki/Wagon-wheel_effect

focalist

#3
Mar 14, 2013, 04:37 amLast Edit: Mar 14, 2013, 04:50 am by focalist Reason: 1

Using a IR pair as a photogate, arduino for the timing, and a bunch of cheap MOSFET's, I drive literally hundreds of watts of LED's for stop-motion.  This particular one is three consecutive 2msec flashes 5 msec apart lit with about 75 watts of LED's, a paint drop landing in a bowl.  I have to revisit that project, I have now amassed just about six hundred watts of white LEDs and built drivers.. and much more efficient and fast switching transistors for them too.  I should be able to dump around 45,000 lumens at intervals down to microseconds with ease.  Since I am just letting the LEDs power up to flash, the cycle time is nonexistant.  Arbitrary delay, duration and interval strobe, solid state. This was shot badly, mainly because I tried to use a relatively slow ISO with a wide aperture - which backfired in terms of having too shallow a depth of field.  That, and 2 msec introduced more blur than I want.  More power and better exposure planning will make for a much better outcome- but suffice to say, using power LED's as a photostrobe is more than feasible.

Tons of light is the key with stroboscopic effects...

fitzgr

#4
Nov 23, 2013, 12:16 pm
Could this be down without the speaker? Say using a servo, and a strobe light. What I'm after is trying to do this live. The servo would vibrate the hose, and the strobe would simulate the shutter of the camera.

Regards,
Grant

robot797

#5
Jan 12, 2014, 01:36 am
i am already working on it

i am kind of stuck on the sinewave
i cant find out how to get a simple sinewave with the power to drive a solenoid

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