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Homemade Camera Crane

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Homemade Camera Crane

Unread postAuthor: MrCrowley » Mon Jun 14, 2010 12:57 am

A little project i've been working on. So far it has cost me $50NZD ($35USD) and I still need to buy some spray paint for it. My friends and I do a little filming just for fun/as a hobby so I thought i'd give a camera crane a go. Wasn't too difficult, you just need to make sure everything is straight.

Crane can turn 360 degrees, reach a height of about 9' and the camera will always be level. The base is a computer chair, pivot is just a big bolt, has 7.5kg of weights on the back and the camera mount is just some bolted metal from a golf trundler and a TV mount haha. It has a chain which can be adjusted to allow for different camera tilt angles (or as shown in the pictures, made to keep the camera level). The bungy cord helps remove the slack in the chain (by pulling the camera back) as the crane arm tilts up. This also helps to keep the camera level.

If anyone wants more pictures, I can post some later. Maybe even a video. Apart from that, anyone have suggestions for improvements?
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Unread postAuthor: Technician1002 » Mon Jun 14, 2010 1:34 am

RC servos for X/Y movement. Use a rate gyro on the rotation so a swinging boom can maintain orientation during the pan. Then you can swing the boom and do a psudu dolly shot.
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Unread postAuthor: CS » Mon Jun 14, 2010 1:51 am

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Unread postAuthor: MRR » Mon Jun 14, 2010 9:55 am

Very nice indeed. If you are interested in camera mounts you should also search on youtube for merlin steady cam, flycam or poor mans steady cam.

The footage with these mounts is amazing.
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Unread postAuthor: Technician1002 » Mon Jun 14, 2010 10:21 am

Some kite cams are stabilized. Commercial solutions are expensive. Home brew can be inexpensive. Rate sensors for pitch and yaw with analog out is as cheap as a Wii motion plus. Brushless coreless motors on the axis with a proper servo amplifier will provide high bandwidth response. (rock solid).
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Unread postAuthor: MrCrowley » Mon Jun 14, 2010 4:02 pm

My friend has a merlin steady cam, think they cost about $1600NZD here, he got it from his dad who is a TV producer. They're a [female doggy] to stabilize with such a heavy camera, very, very tricky stuff indeed.
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Unread postAuthor: Technician1002 » Mon Jun 14, 2010 7:47 pm

Adjusting the servo amp is not too difficult if you have access to a scope. The moment of inertia has to be matched by the overshoot compensation on the servo amp. Set the servo amp for "Critical Damping" of 1.5 with the phase angle of 180 degrees.

Many pre manufactured solutions assume a camera weight range and are not adjustable in those parameters in the servo amp, so with excess or too little mass the damping phase angle and gain is incorrect causing instability.

Servo gain, damping factor, and feedback phase should all be separately adjustable. Feeding the servo amp a dither ramp, ( induced jitter ) and adjusting for the correct phase angel and gain is not difficult. This needs to be done for each axis, 3 or three depending on the mount. Properly done, setup is a 30 minute process to get rock solid stability.

Not all pre manufactured solutions provide these adjustments and are thus limited to cameras with limited lens and body combinations.

My background is in marine Satellite telephone and communications. Gyro aimed and stabilized C band satellite dishes in the golf balls on ocean going ships use this all the time. A ship at sea is not a stable platform. Antenna alignment within +- 1/2 degree is normal.

If you build your own servo amp (not hard if you work with PLL circuits) you need 3 basic adjustments. A DC gain, an adjustable AC gain (lead damping) and integration phase angle (often selected by hand picking AC coupling capacitors).

Mechanical inertia provides a 90 degree lag. The AC coupling cap provides integration with a 90 degree lead when the proper RC pair is selected to match your moment of inertia. The feedback current (not always in phase with the voltage) should be 180 degrees out of phase with the mechanical movement with the gain set for critical damping.

Info on critical damping is here for additional reading.
http://www.cnccookbook.com/CCServoTuning.htm

The Wii motion plus has a solid state 3 axis rate gyro that makes an excellet sensor whether you want pitch and yaw or all three pitch yaw and roll correction. It's not a bad sensor for $20.

By feeding in manual DC offset, you can manually drive the camera to new postions with adjustable slew rates for very smooth pans.
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Unread postAuthor: MrCrowley » Tue Jun 15, 2010 1:24 am

Video:
[youtube]http://www.youtube.com/watch?v=G-11baO5oq0[/youtube]
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Unread postAuthor: Technician1002 » Tue Jun 15, 2010 1:29 am

Nice video. With a yaw gyro the shot of the house could look like a dolly shot. For the tilt down shot a pitch gyro with manual DC offset could power tilt the camera very nicely.

Darn it, Now I need to tear into some Wii Remotes to raid parts., Some RC servos to get motor and gear trains, and build some servo amplifiers. Like I don't have anything else to do at the moment. :shock:
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Last edited by Technician1002 on Tue Jun 15, 2010 11:35 am, edited 1 time in total.
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Unread postAuthor: MrCrowley » Tue Jun 15, 2010 3:22 am

Haha don't think i'll be wiring this up anytime soon but I do have some ideas for manual mechanisms to tilt and pan the camera. As for a dolly, I might just build one separate from the crane because the computer chair base would make it hard to get a decent set of pneumatic tyres on or skateboard wheels (for a dolly track).

Just looked at the video and the quality is pretty shocking compared to the same file uploaded on my facebook. Youtube did give me some error about some index being at the end, probably why it looks so bad.
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Unread postAuthor: Gun Freak » Tue Jun 15, 2010 10:43 am

I get that index error all the time, what does it mean?
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Unread postAuthor: Davidvaini » Tue Jun 15, 2010 4:04 pm

sweet, very smooth functioning..

side question, is the song in the video a really lite acoustical version of Fortunate Son by Creedence Clearwater Revival? especially starting at 42 seconds into the video...
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Unread postAuthor: MrCrowley » Tue Jun 15, 2010 4:50 pm

Yup, it's from the Sons of Anarchy (TV Show on FX) soundtrack/EP "Shelter".
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