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Why are there issues with mixing batteries and cables from different rental houses?


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#1 James Malamatinas

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Posted 22 September 2013 - 07:59 AM

On a recent shoot I narrowly avoided a serious potential problem when I plugged in an Arri 24v battery into a Panavision Alexa. Thankfully the result this time was that the Alexa simply did not take power from the 24V, however the 1st AC I was with, when I bought up the issue, pointed out that we were lucky the Alexa didn't blow due to a difference in polarity with the batteries.

At the time I didn't get a chance to ask any more detail, but could somebody explain exactly what the issue is here - I'm not that learned about electrics, voltage, amps and so forth. What exactly is going on and, in future what sort of things must I be aware of when mixing different components from different rental houses? Also, are there issues connecting 24v batteries to equipment that should usually accept a 12v battery, or does it simply power it for longer?

 

Purely for my own interest, is this something that should be obvious to a 2nd AC? It was a multi-camera shoot and a couple of the other 2nd AC who had been assisting didn't realise this either, but it seems fairly important to know given the consequences!

Thanks in advance for the input.

 


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#2 Michael Kubaszak

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Posted 22 September 2013 - 08:27 AM

Don't know the answer but, this screams of something that should be checked out at the prep. Unless of course production wouldn't give you one, camera flew in that morning etc.  I throw/plug every battery on/in each camera at prep.


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#3 James Malamatinas

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Posted 22 September 2013 - 08:58 AM

Cheers Michael, it was a daily so unfortunately I wasn't part of prep, also the camera I was using was a camera bought over from main unit just for the night. Main unit gear was from Panavision whilst 2nd Unit was Arri just to complicate things a little more! 
 

Definitely agree though, would check this out in prep usually.

 


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#4 Dom Jaeger

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Posted 22 September 2013 - 11:37 AM

Panavision batteries are wired with the reverse polarity to Arri (and every other standard I've come across). What that means is that normally for example a 24V battery with a 3 pin XLR or Canon socket is wired with the negative terminal on pin 1 and the +24V positive terminal on pin 2, while Panavision batteries are wired in reverse. Don't ask me why they chose to do that. The upshot is, you need to only use Panavision power cables with their batteries, otherwise a reverse current is sent through the appliance. Some cameras, like Alexas, are very well protected against reverse polarity or short circuits in the input voltage, others aren't and can blow components.

 

With the amount of voltage, some appliances are regulated to accept a broad range of voltages, Alexas for example will work on anything from 10 to 28V. Others may be 12 or 24V only (though generally there is a tolerance of several volts either side). A 12V battery may supply over 14V when fully charged and run down to 10V before the appliance switches off, and often these days the batteries are more likely to be 13.2V or 14.4V, simply because a nominally 12V appliance can usually handle up to around 17V. The danger is applying too much voltage rather than less, so avoid putting 24V into a 12V appliance. If in doubt, check the voltage specs which are usually written on the back. 


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#5 Phil Rhodes

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Posted 22 September 2013 - 12:01 PM

I don't see a lot of 3-pin XLRs for power - that's an audio thing, although I'm mainly a video guy. In my world, 4-pin XLRs are 0v on pin 1 and +12V on pin 4.

 

I have seen Dedolights using 3-pin XLRs, but that always seemed very unsafe to me.

 

P


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#6 Bruce Greene

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Posted 22 September 2013 - 02:14 PM

I have in my kit a "suicide" pigtail cable for this scenario. I always check polarity before using it.

Glad to know the Alexa will not melt though!
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#7 James Malamatinas

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Posted 23 September 2013 - 12:56 AM

Thanks Dom, that's a very comprehensive answer and exactly what I wanted to know. Like Bruce said, I'm very happy to know that the Alexa had adequate protection!

I've never spent much time considering the specific configuration of pins for different cables and what each pin does, but are there many other situations like this where actually knowing that information would come in handy on set, either in configuring a camera or other appliance, or for troubleshooting?

 

 


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#8 Keith Walters

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Posted 23 September 2013 - 03:27 AM

Everybody seems to blame Panavision for this problem, but the reality is they were supplying 24V batteries with 3-Pin Cannon/XLR sockets long before Arri started making 24 Volt cameras. The first 24V Arri camera was the 35mm 535, which came with NiCad batteries with 3 pin XLR sockets, wired the reverse of the Panavision standard. Just why Arri did that is beyond me, and I've never gotten a coherent answer from Arri engineers.

The only explanation I can think of is that because Pin 1 in negative on a 4-pin 12V socket, they thought it logical that pin 1 should also be negative on a 3-pin socket.

If they simply wanted to stop people from using Arri batteries on Panavision cameras (or vice versa) you'd think it would have been more sensible to simply use pins 1 & 3.

But wait, there's more! Like most Panavision cameras, the Arri 435 has a protection relay that only activates when the correct polarity battery is fitted. With the PV design, they have a silicon diode that prevents reverse polarity from reaching the relay closure circuit, so if you get reversed polarity, nothing will happen. (They both use relays rather than simply using diodes directly, because otherwise you lose quite a bit of power just heating up the diode)

But the Arri 435 feeds the relay control circuit through a Polyswitch (self resetting fuse), and the fuse "blows" if you have reversed polarity. It wouldn't really matter I guess, except that the Polyswitches are only good for a limited number of "blows" and after a while the circuit stops operating.

The easiest fix is to just replace the Polyswitch with another diode, and then the problem never occurs. If you're totally anal you could fit a new Polyswitch in series with the diode, but it doesn't really serve any useful purpose.

Most experienced camera assistants will have 3-pin reversing leads as part of their kit.

Again WTF Arri chose such a brain-damaged system of protection is beyond me. Perhaps they wanted to punish people for using Panavision cameras.

It was a major PITA when Panavision Australia were Samuelson Film Service, carrying both Arri and Panavision cameras!


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#9 Dom Jaeger

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Posted 23 September 2013 - 08:58 AM

Everybody seems to blame Panavision for this problem, but the reality is they were supplying 24V batteries with 3-Pin Cannon/XLR sockets long before Arri started making 24 Volt cameras. 

 

Fair enough Keith, Arri were the dunderheads. 

It's more fun to blame Panavision though, especially if you've worked for them.  ;)

By the time I started in the service department at Sammies in '96 the Arri version seemed the more sensible and already accepted standard. 

You have to admit, it does keep it simple to make pin 1 negative across connectors. 


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#10 Keith Walters

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Posted 24 September 2013 - 05:41 AM

By the time I started in the service department at Sammies in '96 the Arri version seemed the more sensible and already accepted standard. 
 

??? All the 24V batteries I had anything to do with at Sammies  were wired to Panavision standard. If I remember correctly, we never bought any Arri 24V batteries, apart from the small ones for the SR3s. We actually made our own dual voltage 12/24 lead acid packs and accompanying chargers, but they mostly got used in 12V mode for running the older cameras and monitors.

 

We used to have endless problems with overseas companies bring their own Arri cameras but not wanting to pay the airfreight for the batteries, and wanting to use ours.

 

The worst ever job I had anything to do with was when I was at Cameraquip, and a large production had rented 435s from both us and Panavision, and then pissed off to the middle of the Simpson Desert somewhere. Naturally Cameraquip used the Arri polarity....

 

To top it off, one of the assistants was a certain Brain Damaged individual from New Zealand with the  initials I.T. who I am sure you have learned to despise, if somebody hasn't crowned him with a 4K ballast yet....


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#11 Rob Vogt

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Posted 26 September 2013 - 08:07 PM

Also be weary about Convergent Designs vs Sony/Astro Design onboards which use the same 4 pin hirose but reversed polarity. The nanoflash is the same wiring as a Gemini, which is input protected, but the Nanoflash is not-or at least not as well protected. Same thing with the Genesis accessory and Alexa ethernet port. The stedicam pro 3 pin Male/Female lemo is reversed polarity from the Panavision 12V. The older heden  c-motion motors used to be wired differently from Preston but the newer c-motion motors changed to use the same pin-out. The Barton box has the same connector but different wiring as the camera run-stop port on the MDR.

 

Point being just because the plug fits doesn't make it right. If you're not sure ask during prep- someone at the rental house will know.


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#12 Matthew Parnell

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Posted 06 October 2013 - 05:33 AM

Phil, 4 pin dedos are 12v, 3 pin are 24v.
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#13 Stephen Williams

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Posted 06 October 2013 - 06:44 AM

I don't see a lot of 3-pin XLRs for power - that's an audio thing, although I'm mainly a video guy. In my world, 4-pin XLRs are 0v on pin 1 and +12V on pin 4.

 

I have seen Dedolights using 3-pin XLRs, but that always seemed very unsafe to me.

 

P

 

 

3 Pin seems to be 24 v where 4 pin is often 12 v (Sony etc)


 


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#14 Phil Rhodes

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Posted 06 October 2013 - 08:39 AM

That really is catastrophically silly in an environment where 3-pin XLRs are usually connected to audio gear which is likely to react very poorly to having 24V stuffed up it...


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#15 Larry Nielsen

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Posted 07 October 2013 - 10:17 PM

One has to remember that before Arri went Three pin, they used to be four pin. And Panavision has been three pin for longer than I can remember. So its only fair to say Panavision didnt screw it up. The three pin configuration of whats hot and not for Arri also changes from Camera house to Camera house. I know you can't use your personal camera on a Clairmont Camera battery unless you use one of their power cables, or have made a jumper yourself to connect between the battery and the cable. Is this a bad thing? Not really, I don't know to may people stealing Claimont camera batteries for their own personal cameras, And no I own no cameras, just something that happened on a show I did when Clairmont did the support, but the DoP owned the cameras.


Edited by Larry Nielsen, 07 October 2013 - 10:21 PM.

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