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Alexa Dionic HC Power Issue/Readouts


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#1 Dave Chameides

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Posted 27 March 2011 - 09:51 AM

Shooting with the Alexa using Dionic HCs. While we aren't having a power issue per se, as soon as we power up the cameras, the readouts on the batts shoot down to 1 immediately. Power on the camera lcd says it's fine and we are getting decent run times so we've just chosen to ignore the anomoly. That said, it's still troubling me as I haven't seen anything like this before. Same thing happening with two cam bodies and my batts as well as rental houses. Anyone have any thoughts or experiencing similar issues?
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#2 Alec Jarnagin SOC

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Posted 27 March 2011 - 11:23 AM

Dave,

Just curious, are you running the camera in 12V mode or 24V? I have not flown the camera yet, but I have heard it prefers 24 Volts. Half the voltage equals twice the amperage, etc.
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#3 Lawrence Karman

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Posted 27 March 2011 - 11:31 AM

If i'm not mistaken, that "1" means the battery calculates it will run the camera for 1 hour at that current, which is not surprising and actually pretty good. Plus whatever else you are powering: Cinetape, Preston, OB1 recorder, HD transmitter or Modulus, GPS?
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#4 RonBaldwin

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Posted 27 March 2011 - 12:14 PM

I think that must be "normal" as the same thing happens to me (powering from two hc's on the sled). As mentioned above I think it is showing approx run time at current draw. I seem to get about 35 min on a set of hc's powering the alexa, cinetape, preston and nebtek.
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#5 Afton Grant

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Posted 27 March 2011 - 08:04 PM

Just curious, are you running the camera in 12V mode or 24V? I have not flown the camera yet, but I have heard it prefers 24 Volts. Half the voltage equals twice the amperage, etc.


This is a rumor I too have heard and actually was hoping someone could explain exactly what "prefers 24V" means. I shot for 12 days with the thing, 4 of which were in the unforgiving heat and dirt of Haiti. Single onboard V-Mount the whole time. Never a problem. Is 24V needed for certain functions? Certain fps? The only thing I could think of being affected would be the running of 24V accessories, but I believe the camera will put out 24V regardless of what's fed into it. If someone could please correct and/or educate me....

Thanks!
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#6 RonBaldwin

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Posted 27 March 2011 - 08:55 PM

What Stephan at Arri told me was that it only accepts 12v from the onboard. If I remember correctly (doubtful) he mentioned that the 24v was mainly for the aks. My next show is with the Alexa so maybe I will try it and report back about run times...might just have to.get a cable to power the cinetape from the sled instead of the 3 pin from the camera?
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#7 Benjamin Treplin

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Posted 27 March 2011 - 09:23 PM

The Alexa has an internal voltage buster that supplies the RS ports with 24V if the input voltage is less than 24V. The camera takes anything from 10.5V to 34V. So it is more efficient to power the camera with a power source above 24V because there is no need to boost the voltage on the RS ports.
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#8 RonBaldwin

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Posted 27 March 2011 - 10:09 PM

The Alexa has an internal voltage buster that supplies the RS ports with 24V if the input voltage is less than 24V. The camera takes anything from 10.5V to 34V. So it is more efficient to power the camera with a power source above 24V because there is no need to boost the voltage on the RS ports.


so I guess it would blast through one hc pretty fast -- cn the threshhold be changed? The camera was shutting down around 21/22 volts (I usually watch that closely...but with today's moron hack directors who never cut it just happens).
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#9 Benjamin Treplin

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Posted 27 March 2011 - 11:32 PM

cn the threshhold be changed? The camera was shutting down around 21/22 volts (I usually watch that closely...but with today's moron hack directors who never cut it just happens).


I don't know. I was wondering if it's possible to feed 12V through the Fischer connector. Guess not.
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#10 RobVanGelder

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Posted 28 March 2011 - 06:53 AM

It makes more sense to use 24 to 28 volts because your batteries will last longer. Not only is there no coversion (booster) nesseccary, the current draw from the batteries is lower too, probably halved. That means your batteries will live longer!
But: if the rental house supplies the batts i tend to use the onboards and keep my own batts for the aks.
Rob
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#11 John atkinson

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Posted 28 March 2011 - 07:19 AM

On my first Alexa jib the DP handed me the camera and said "this doesn't like Dionics" . Use the hytrons on this camera. No problems.


JA
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#12 Jens Piotrowski SOC

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Posted 28 March 2011 - 10:48 AM

Use the A/B hot-swap adapter on the back of the Alexa and 2 Dionics simultaneously, works great.

http://1.bp.blogspot...ilmcastlive.jpg

also to my knowledge the ALEXA is a true 24V camera, meaning it works internally with 24V, a 14.4V battery will be send through an internal DC/DC converter and will results in higher amperage draw.

85 W power draw at 24V equals 3.6 amps
85 W power draw at 12V equals 7.2 amps

"Power Management
When using the BAT connector and one or more onboard battery
adapters simultaneously, the camera power management ensures that
the power source with the highest voltage level is used. When the
voltage level of one power source drops below the level of the other, or
a power source is disconnected from the camera, the power
management automatically switches to the other power source,
avoiding shutdown of the system.
So as an example, one could use a 12 V onboard battery as backup for
the main 24 V battery, or power the camera from the 24 V battery while
on a tripod and use the 12 V battery for fast switching to handheld
mode by just unplugging the power cable.
When using two onboard battery adapters with batteries in parallel
(one on top and one on the back), they are treated as one source by the
camera. This allows combining small batteries with less load per item
into one strong power source"
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#13 MarkKaravite

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Posted 28 March 2011 - 09:56 PM

I asked Jurgen from Arri the 12v vs 24v question when he was at Fletcher for an Alexa demo. He concurred that the Alexa is a 24v system, and upconverts 12v inputs to 24v. That's why the RS connectors work with a 12v input. With that said, Jurgen pointed out that the upconverter is so efficient, that there is not an appreciable difference between 12v & 24v inputs when it comes to run times. I also tested the Arri 2 pin power input with a 12v source, and it did not work. The only way to input 12v is through the Anton Bauer plates.

I love the dual battery system on this camera. In studio mode, we always run a battery on the back in combination with a 24v block battery. Theoretically, the camera never has to shut down. Moving on, just pull the block, move the camera and start framing the next shot. Also, gone are the worries if there is another take in the block battery, because of the auto switching to the 12v power source. It is true that the camera gets poor run times with a single Dionic (HC or 90) on the back. For handheld shots, we carry Hytron 140's for single battery work. Not only do the Hytrons give you decent run times, it offsets what is normally a slightly front heavy camera with Master Primes. As Jens points out, a Dionic hot swap rig on the back would achieve the same advantages of the Hytrons.
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#14 Sean Jensen

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Posted 29 March 2011 - 09:57 PM

Hello all.

I'm on my second Alexa series and am running the camera off one Dionic HC through my sled with no problems. On the last show, before I had a right angle cable made for the camera, I was using an onboard battery. The Alexa with an Angenieux Optimo 28-76, clip-on matte box and eyebrow, Wevi or Boxx and a battery is just too long for me. An Anton Bauer hot swap adapter would only add to that. I had the cable made and that extra two and a half inches less really makes a difference. I actually hit myself in the head a couple times while panning with the onboard battery. The single Dionic HC works fine for the camera and all accessories except I power the Boxx from the accessories out on my sled. It's power hungry and I find it drains its battery almost as fast as the camera drains its. I get decent run times and change batteries at about the same rate as I would on a film show.

Sean
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#15 Matthias Biber

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Posted 30 March 2011 - 10:52 AM

Low power warning is adjustable in the menue. There are two settings one for the onboard batt and one for 2 pin Fisher. If you want to run 12V through the Fisher conector, instead of 24V, you have to set the low power warning correctly, first.
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