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Alternating voltage problem

electrical power 12v 24v camera power intermitent

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#1 TJ Williams Jr.

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Posted 03 May 2013 - 08:39 PM

Hey guys,

 

I have a custom top and bottom stage on my rig (wired by Terry West), and am wondering if you guys could help me figure out an electrical issue. Before you dismiss me and tell me to take it to Terry, I've been working on this with him also, but figure I'll cast a wide net for answers.

 

The issue is that my camera power has a tendency to drop out, and it seems pretty much at random. Its both the 12v and 24v power.

 

Whats strange is that the power doesnt drop all the way out- it just drops from 14.4v or 24v to about 9v, and will shift back and forth from one to the other, but never anywhere in between or lower. Sometimes this shift is very quick maybe just a few seconds, and sometimes it will be minutes. Obviously this shuts down any camera that is being powered by the rig, so I have resorted to powering things on camera for quite some time while trying to figure this out.

 

I went through and spread the pins on the post (XCS post) to make sure each connection was nice and solid in the post / bottom stage connections, but the problem is still persisting. I'm not really an electrical engineer, so before sending this in to Terry one more time I was going to open it up here and see if anyone has a good idea. 

 

Hit me with your best shot! I'm stumped.

 

-TJ

 


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#2 Victor Lazaro

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Posted 03 May 2013 - 08:56 PM

What rig is it? what modification did Terry do? What batteries and accessories are on your sled? Photos maybe?


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#3 TJ Williams Jr.

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Posted 03 May 2013 - 09:01 PM

What rig is it? what modification did Terry do? What batteries and accessories are on your sled? Photos maybe?

 

The Rig is essentially fully custom. Its based around the XCS post, but both the top and bottom electrical distro boxes are custom machines, and custom wired, so he didnt really mod it from anything. The battery bottom stage that I use is from Rig Engineering, and its a basic three battery pro style setup with two AB's top and bottom towards the rear, and one AB diagonal under the monitor. The diagonal AB is my camera power position for 12v, and my back top battery is system power (which works great). That leaves my back bottom battery for AUX power or 24v camera.

 

I run Dyna 190WH AB's on it, but before you go off on my off brand batteries this power situation happens no matter what batteries I put on my sled. Often times I will run whatever AB back battery comes with the Alexa for Handheld on my rig, and even so it still has the power drops. I think it must be something to do with the Sled because it also happens on different camera power cables. It happens on my 12v Alexa, 24v Alexa, 12v Red, and so on.

 

no good pictures available right now. I'm cooking dinner.

-tj


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#4 Afton Grant

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Posted 03 May 2013 - 09:19 PM

Do you know what gauge the wiring is throughout the rig?
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#5 TJ Williams Jr.

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Posted 03 May 2013 - 09:23 PM

Do you know what gauge the wiring is throughout the rig?

Thats an interesting point.

 

I think I know what gauge the wiring is inside of the custom boxes I had made. I think its 20 gauge, but I dont know what gauge is inside of the Rig Engineering battery stage, or the XCS post for that matter (although I somehow think without knowing that the wiring in the XCS post is going to be adequate for powering a small car)... This does seem to happen only on cameras like the Red, and Alexa with heavy power draws though. Maybe I should check out the wiring inside of the Rig Engineering bit.

 

Thats a good idea of a place to look. Thanks!


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#6 Eric Fletcher S.O.C.

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Posted 03 May 2013 - 10:07 PM

XCS is 14 gauge power

20 is too small for an Alexa or Red or any Sony full size camera
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#7 Mark Schlicher

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Posted 04 May 2013 - 12:53 AM

Does your rig have any voltage regulation circuitry? If so, I'd suspect that. The kind of random fluctuations you describe doesn't sound to me like they are related to wiring gauge.


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#8 TJ Williams Jr.

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Posted 04 May 2013 - 01:37 AM

XCS is 14 gauge power

20 is too small for an Alexa or Red or any Sony full size camera

 

Great to know that the XCS is wired at 14 gauge. I'll bring that up with Terry when I bring it in because I dont think my wiring is that fat right now. I would expect too thin of wire to cause heat issues though not power fluctuations, but its a good place to start. Thanks Eric. 

 

 

 

Does your rig have any voltage regulation circuitry? If so, I'd suspect that. The kind of random fluctuations you describe doesn't sound to me like they are related to wiring gauge.

 

As far as I know Mark there is nothing in between the batteries and the power outputs except for circuit breakers. The power is passed straight through. 

 

Do you guys think a short of some kind could be causing this? Some sort of voltage loss to the housing perhaps?

 

Seems so weird to me. 


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#9 Eric Fletcher S.O.C.

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Posted 04 May 2013 - 01:50 AM

Is it only during 24V operation. If so it's your batteries and their protection boards shutting them down
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#10 TJ Williams Jr.

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Posted 04 May 2013 - 01:52 AM

Is it only during 24V operation. If so it's your batteries and their protection boards shutting them down

 

It happens during both 12v and 24v operation, and seems to happen more frequently at 12v as opposed to 24v although I havent done any sort of empirical test on that yet. Just a feeling. 


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#11 Eric Fletcher S.O.C.

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Posted 04 May 2013 - 02:39 AM

Then it's a battery and undersized wiring issue. Even though you have 14ga wire up the post. Your effective gauge is 20 because that's the smallest wire in the rig. 20 ga can cause up to a 3 volt drop in our sleds
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#12 Alan Rencher

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Posted 04 May 2013 - 03:52 AM

Are there diodes installed? The batteries may be freaking out of they are unbalanced and trying to charge each other. What do you think, Eric?
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#13 Mark Schlicher

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Posted 04 May 2013 - 03:41 PM


 

Whats strange is that the power doesnt drop all the way out- it just drops from 14.4v or 24v to about 9v, and will shift back and forth from one to the other, but never anywhere in between or lower. Sometimes this shift is very quick maybe just a few seconds, and sometimes it will be minutes.

 A sudden, random, stepdown from 14.4 or 24V to 9V that lasts between seconds and minutes, regardless of camera and unrelated to the power draw sure sounds like an issue with some kind of circuit (or, I suppose, an intermittant connection). I would think that any voltage drop related to wiring gauge would be consistent, except in the case of powering on a new accessory with a high initial draw. Random fluctuations for no apparent reason don't make sense to me as wire-gauge-related.

 

Good luck, hope you track it down quickly.


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#14 Afton Grant

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Posted 04 May 2013 - 06:56 PM

If a wire's gauge is too small to power a specific device, it will heat up, which will increase resistance, which will decrease the  voltage.  If the gauge is way too small, it will heat up and up and up, get more and more resistant until a tipping point is reached and the device can no longer run.  At this point, the demand for power disappears, the wire will cool down (if it hasn't been melted) and if you were to test the voltage with a multimeter, it will probably give a normal reading.  This is deceptive, however, since a meter alone will not draw the same current as a camera.  


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#15 Eric Fletcher S.O.C.

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Posted 04 May 2013 - 08:36 PM

 A sudden, random, stepdown from 14.4 or 24V to 9V that lasts between seconds and minutes, regardless of camera and unrelated to the power draw sure sounds like an issue with some kind of circuit (or, I suppose, an intermittant connection). I would think that any voltage drop related to wiring gauge would be consistent, except in the case of powering on a new accessory with a high initial draw. Random fluctuations for no apparent reason don't make sense to me as wire-gauge-related.

 

 

 

 

That's EXACTLY what happens with undersized wire


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