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12v versus 24v?


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#1 Tom Wills

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Posted 30 November 2010 - 08:44 PM

I've begun work on piecing together a sled (it'll be a bit of a Franken-rig 3A, but it's a big upgrade from what I have now). However, the starting point of a sled I am looking to purchase does not include any electronics, and the wiring was all done by the previous owner. I'm planning on re-doing it all from scratch, and hopefully with some professional help.

In beginning to work up some designs, and it's made me really curious as to whether I need 12v or 24v power for the sled. As more and more work moves to digital cameras, most of which are usable on 12v, would it make any sense to focus on having a really good 12v system, or would it be better to just go 24v from the start. Right now, the market I'm in doesn't even have any film cameras, let alone anything higher-end than a RED. And, while I'm sure I'd love to operate some film jobs, I think that the level that I am (and probably will be) at for some time will keep me planted in the video world. I also anticipate that this sled will eventually be replaced, once I do move up in skill and funds.

So, what do people think? Is a 12v only sled viable? I really appreciate the help!
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#2 Alfeo Dixon SOC

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Posted 30 November 2010 - 09:01 PM

You don't have the luxury of choosing you camera... So if you want to give me all your calls for jobs that fly film cameras... Go right ahead, I'll take it!
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#3 RobVanGelder

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Posted 01 December 2010 - 12:27 AM

12 volt is out - you need to think at least Li-Ion type of batteries or you might have problems in the future.
That means 14.4 or 28.8 volts nominal, where the batteries can reach 17 volts when just of the charger.
It is important to make your electronics in such a way that they can handle these voltages.

It also shows you that if you need a constant 12 or 13 volts output you need additional electronics to keep it at that level.

My "franken-rig" which has parts and electronics of the Steadicam Master is a double voltage system, switchable between 14/28 volt.
It also has a Downconverter to make 13.2 volts constant for anything that needs that 12 volts. (transmitters, follow focus, lcd, etc.) Some accessories really have a top voltage @ 15/16 volt that they can handle.
Keep in mind that down converting is always better than up-converting, although I have now found some reliable and lightweight 12 to 24 up-converters that van handle up to 10 amps.

On my special request this company even made a 12 to 28 volt / 15 Amp up-converter which I am about to test this week. (with 435/high speed).

Rob
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#4 Tom Wills

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Posted 01 December 2010 - 12:46 AM

You don't have the luxury of choosing you camera... So if you want to give me all your calls for jobs that fly film cameras... Go right ahead, I'll take it!


Good point Alfeo. It is something to consider - what if a job came to town with a 24v camera?

12 volt is out - you need to think at least Li-Ion type of batteries or you might have problems in the future.
That means 14.4 or 28.8 volts nominal, where the batteries can reach 17 volts when just of the charger.
It is important to make your electronics in such a way that they can handle these voltages.

It also shows you that if you need a constant 12 or 13 volts output you need additional electronics to keep it at that level.

My "franken-rig" which has parts and electronics of the Steadicam Master is a double voltage system, switchable between 14/28 volt.
It also has a Downconverter to make 13.2 volts constant for anything that needs that 12 volts. (transmitters, follow focus, lcd, etc.) Some accessories really have a top voltage @ 15/16 volt that they can handle.
Keep in mind that down converting is always better than up-converting, although I have now found some reliable and lightweight 12 to 24 up-converters that van handle up to 10 amps.

On my special request this company even made a 12 to 28 volt / 15 Amp up-converter which I am about to test this week. (with 435/high speed).

Rob


Rob,

I'm already using a whole host of Anton Bauer ProFormers, which (I believe) are 14.4v. I'm probably going to pick up some Dionics in the future. Would I be incorrect in thinking that most professional gear could use the 16+ volts that a battery can be off the charger? So far, I've never had a problem running any of my accessories, or accessories I've rented straight off of the battery, except for one really cheap video transmitter a DP loaned to me. Would it be worth it to do voltage regulation at this point? Getting the kind of amperage on a voltage regulator needed to drive all of the electricals of a sled seems like overkill to me - but then again, XCS does it!

This is why I love this forum - with every question I ask, it seems I end up getting tons of other answers I never would have thought to ask about.
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#5 Eric Fletcher S.O.C.

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Posted 01 December 2010 - 01:18 AM

Getting the kind of amperage on a voltage regulator needed to drive all of the electricals of a sled seems like overkill to me - but then again, XCS does it!


XCS does it to run the camera.

it's folly to have a 12v only rig (12 volts covers anything that uses a 14.4 volt battery or less) 12V only and you can't fly any modern film camera, the Alexa runs on 12 or 24v but since Arri accessories are now 24V you have to rely on the cameras up-converter...

It's not hard to make a rig that does 12 or 24V, and it's certainly not worth the future loss of jobs to not make it voltage selectable. Remember one of my Mantras. NEVER let your gear limit your work
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#6 RonBaldwin

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Posted 01 December 2010 - 11:09 AM

...NEVER let your gear limit your work...


you are a loser Eric -- it's NEVER let your body limit your drinking.

Hi Tom -- It's so easy in the grand scheme of things to make a voltage selectable sled (what -- some wire and a switch?). Don't even think about not having that function. We old-timers went through that bs in the early days when steadicams were 12v only. Rigging extra batts and using converters bring the suck. Don't embrace the suck.

rb
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#7 Tom Wills

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Posted 02 December 2010 - 04:52 PM

Thanks everybody for all the responses. Glad I didn't make a bad choice early on that would require re-wiring the sled entirely later down the road!
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#8 RobVanGelder

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Posted 03 December 2010 - 03:21 AM

So the consensus seems to be: make it 24/12 volt switchable at least.

Still I want to emphasize the fact that it is a good thing to have a stabilisation on the voltage. I bought a video transmitter some time ago that really could not handle more than 14 volts.
The other day I tested the 12 to 28 volt up-converter that I had ordered. It seems to work well with a 435, giving only 0,2 volt (27.67 to 27.47 volts) drop when shooting 125 fps. But the camera had no film yet, will test that another time.
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#9 Douglas John Kropla

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Posted 11 January 2011 - 05:50 PM

...NEVER let your gear limit your work...


you are a loser Eric -- it's NEVER let your body limit your drinking.

Hi Tom -- It's so easy in the grand scheme of things to make a voltage selectable sled (what -- some wire and a switch?). Don't even think about not having that function. We old-timers went through that bs in the early days when steadicams were 12v only. Rigging extra batts and using converters bring the suck. Don't embrace the suck.

rb

Hey Ron,
I am in the same boat with Tom, do you or anyone else have a wiring diagram for a simple 12/24 volt system? Should I ask Terry West maybe?
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#10 Jess Haas SOC

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Posted 11 January 2011 - 10:45 PM

You just run two 12volt batteries in series to make 24volts. So you connect the positive of one to the negative of the other. For 12 volt accessories you can tap a single battery by going from the center of the two batteries for a 12v positive or you can use a separate battery. Wiring a switch of course adds a little more complexity. Don't have a diagram handy so I doubt that made too much sense.

~Jess
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#11 Eric Fletcher S.O.C.

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Posted 11 January 2011 - 11:51 PM

Careful Jess you can in certain circumstances get a reverse polarity 12 volt backfeed if you pull the "main battery before the "booster" battery. There is a great Circut diagram in one of the old Steadicam letters that uses a relay to provide a Saftey
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#12 Douglas John Kropla

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Posted 12 January 2011 - 09:58 AM

Thanks Jess and thanks Eric. It is the addition of the switch that is twisting my brain. Also to prevent one batt back loading into the other a schottky diode or a regular diode could be used correct?

I have 3 pin lemo's on my topstage. I have 4 cables going up from the bottom, could I just run a common ground to my 12/24 lemo(pin 1) and two of the 12 volt lines (pins 2 and 3) as power? Then jump the ground over to the other lemo(aux power) with the last 12volt line? This would give me 12 volt for FF/AUX plus 12/24 power with the correct cable to whatever camera came my why, yes no?

At the bottom I have two IDX plates with 4 pin xlr into the bottom stage. I take one batt positive line and branch it to pin 2 of the xlr and that goes up the pipe as the separate 12/24 volt line? With an inline fuse?

Sorry Tom I hijacked your thread here.
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#13 Douglas John Kropla

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Posted 13 January 2011 - 03:50 PM

I found a 12/24 wiring diagram that works for 2 or 3 batteries. Tom do you want it? I spent the last day wiring up my sled and it works great. I got this from a fellow from OZ named Trevor.

I am a little worried about the backfeed problem so I will attach the diagram here.[attachment=6227:12:24_wiring.jpg]

Edited by Douglas John Kropla, 13 January 2011 - 03:55 PM.

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#14 RonBaldwin

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Posted 13 January 2011 - 04:11 PM

FWI...Pro has all their schematics on their site if you want to see how they do it. No secrets there...just a simple well built sled.
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#15 Douglas John Kropla

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Posted 13 January 2011 - 06:05 PM

Thanks Ron, I will look into that. Does the schematic i'm using pose any problems in regards to one batt backloading as Eric mentioned. Thanks for the advice and Tom I am sorry I hijacked your thread.
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