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#1 Chris Freilich

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Posted 07 December 2015 - 06:13 PM

Hi all,

 

Just starting out, freshly out of a great workshop with Chris Haarhoff and Andrew Rowlands, and I've finally gotten together my equipment package, which is a Pro CineLive rig with a Gen 4 battery rack.

 

I have questions about how to power cameras and accessories off of this rig. There is a 12v/24v switch, and a large number of different connectors which seem to provide 12V, 24V or both.

 

I assume that the 12V/24V switch switches all of the outputs that can supply both voltages? What about the outputs that are 12V only... will they still supply 12V power when in 24V mode? Same question for the P-Tap outputs?

 

And how do I figure out which of these outputs is meant for which devices? I just received my Preston, for example, and am not sure how to order a proper power cable for it.

 

Further, I understand that the Alexa can be powered by either 12V or 24V. Is this true, and if so, what are the attendant benefits of each? I've read a recent thread about problems with ground loops in 24V mode, though to be honest I didn't really understand the details of that thread either.

 

I'm basically totally lost in regard to best practices in powering camera and accessories with my rig. Any information or advice would be greatly appreciated!

 

Best,

 

Chris


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#2 brett.mayfield

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Posted 08 December 2015 - 11:45 AM

Hey Chris

 

Im no power expert, but I also own a CineLive and have tried to use the various power outputs in as many ways as possible.

First, to address your Preston cable issue: preston makes cables, check their website in the downloads section. you can also check with Media Blackout or Terry West. I have two kinds of Preston power cables, the first is Ptap (I had a 12v Lemo to Ptap splitter made by Alan Rencher of Media Blackout) and then there is 12v Lemo (from CineLive) to Preston.

 

Your rig has three battery plates, bottom front (bf), bottom back (bb) and top back (tb). BF and TB are 12v only and they provide power to your camera and accessories (aks) in 12v. the BB is auxiliary and provides 24v power to camera and aks. You lower junction box has three breakers: Cam, Acc/Aks, and Aux. In order to use power from any of your plates, you must depress the respective breaker. Cam and Acc will only supply 12v from BF and TB to your Camera and Aks, as noted before. the Aux breaker will allow you to send 24v power to the noted outputs, as well as to the Ptap labelled Aux on the right hand side of the lower electronics. be careful with this ptap - it has been known to fry a few recorders. If you are using electronics on the bottom of your sled, use the left-hand ptap (labelled Acc I believe, I dont remember...) but it is 12v always.

 

While Alexa can technically run 12v, your sled cannot provide the proper wattage (I think thats correct...), so you will have to flip your switch from 12v to 24v. This will draw power from your Aux battery plate (BB, remember?!) and will provide 24v power to you camera and all of the 12/24v Lemo outs. Be sure that your electronics can handle this load. Teradek, preston, they are fine, they will regulate the power appropriately up to 31v I believe.

 

Each power output is pretty much arbitrary, meaning preston doesnt need to go to any one of those in particular. But it would make sense to have the 3-pin lemo made for your Preston, as there is more than one on your sled and it is more or less standard. I wouldnt recommend the hirose, but that being said, I did have a hirose cable made for my smallHD to run off the Hirose on the upper electronics.  Generally, if you are going to have a cable made, you will say "I need a preston power cable for CineLive to MDR3" and the cable manufacturer will have the proper pinout diagram to make you a cable. But ask them any questions. I always do, because Im kinda ignorant when it comes to power.

 

When I am running an Alexa, I tend to run the camera power from the sled in 24v, with my most serious battery (like an HCX if there are limited supplies) on the Aux (BB) plate and then I run my aks off of the sled rather than off of the camera. Generally, I will never have to change the Cam/Acc (BF, TB) batteries on a shoot day, maybe once. But the Aux (BB) will change throughout the day. You will need a CineLive/Alexa cable made (I always suggest duplicates).

 

I also will use the Aux/BB plate as a spare battery holder and for extra weight/dynamic balance. When I am on the kind of set that is cart-less or we splinter off, I throw and extra battery on this plate, even when only in 12v, because i then have a spare battery that is actually working as balanced weight. great for extending the post and getting those floor-grazing walking shots with the CineLive's somewhat abbreviated post. then once the camera battery is wasted, swap your Aux battery to camera and youre still golden.

 

have a good one!

 

brett.


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#3 Chris Freilich

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Posted 08 December 2015 - 03:55 PM

Thanks Brett, that is very informative! I'm going to have to print it out and study it a bit!


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#4 Chris Freilich

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Posted 15 December 2015 - 06:43 PM

So, I just got back from my first Alexa job, and I tried to use my brand new 24V power cable from Terry West, and when I switched the 12V/24V switch to 24V, the camera breaker pops immediately. New cable, new CineLive sled, new batteries. Any idea what I'm doing wrong?


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#5 brett.mayfield

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Posted 15 December 2015 - 08:38 PM

hmm...I'm hesitant to blame the cable if Terry made it. your jumper block is for Gen 4 correct? if you know how to use a multimeter, try taking it to the cable. I'm not sure...perhaps call Pro.
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#6 Chris Freilich

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Posted 16 December 2015 - 08:40 PM

I wrote to Terry yesterday about the issue I had. He had built me a replacement cable and was going to send it out to me, but then he said I could bring my sled and batteries to him if I wanted to go over everything with him. I went up this afternoon and we plugged everything in, and it seems pretty clear that the sled is providing the proper 24V to the ports and the cable is properly bringing that power to the camera. We tested his newly built replacement cable, with the same results. Without the Alexa on there, there is no popping breaker. So, it seems like perhaps there was a ground leak somewhere it the camera system, is the best guess. I'll have to wait to fly an Alexa again to see if I have the same problem. Terry was great and very responsive to the possibility that it could have been a problem with a cable he made, even though it was not.


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#7 Sanjay Sami

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Posted 18 December 2015 - 12:38 AM

Terry is absolutely fantastic. I have had nothing but good experiences with him, and have never had an issue with the 30 odd cables (maybe more) he has built me. A gyro battery hot swap box he made me fell off a quad some years ago and was bent out of shape, but still works fine.


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