Powering BMMCC and VA from same battery

Hello,

I just like to know if it is possible to power the BMMCC and the VA from the same battery. I like to use LP-E6 battery adaptors on the camera and the video assist and connect both to one power source (7,4V LiIon battery pack). Will this cause a problem with the common GND connection (both are also connected by HDMI cable)? I like to avoid a failure caused by power GND and signal GND offset...

Best regards

Markus

Hi Markus,

I was hoping to see some answers to your question. I have tried something similar and ended up with a defunct HDMI. In retrospect I suspect the problem was related to the common earth and I asked the local repair shop proprietor who specializes in higher end video cameras for an opinion. His comment surprised me – he thought I was unlucky and that the HDMI failure was unrelated. As I feel that I might not have made myself clear I would like to hear other opinions.

What I was trying was a little more complicated than your proposal. I was using a DP6 monitor that has a generous voltage range of 6-18 volts and a Panasonic XC-X900 that requires an external supply of 9.4 volts. To power the camera I had two 7.2volt NP-F970 batteries in series giving ~ 14.4 volts that I regulated to the required 9.4 volts with an LM 318T regulator circuit. To power the monitor I could select one or other of the batteries meaning that earth could be at the same potential as that for the camera or higher depending which battery I had selected. My loss of HDMI out on the camera did not happen instantly, I had some use from the set-up. I have replaced the camera but I am not keen to repeat the experiment without further advice.

Alastair I agree with your repairman, HSMI failure not likely costed by your power setup, since you had the voltage regulated, which should have also isolated the two outputs, this is how a BDS works, it regulates and isolates the various outputs from the one common higher voltage battery. If the battery setup,was the issue, it would have blown right away.

Markus and Alastair, if you use a good Battery Distribution System (BDS) that regulates the power to 7.4 volts and isolates the two outputs, like the Atomos Power Station, which uses two Sony L batteries and distributes power to 2 isolated outputs at 7.4 (8.2 VDC max, which is a 7.2 battery max rating), and comes with two Cankn E6 dummy battery connectors. I use this with my Micro and VA setup, worked well if you used the large L batteries.

Also,you can use the 14.5 VDC camera batteries, and use the VA power jack on the side, and the power connector on the Micro camera dongle, or in case of a camera without a 12VDC power jack, the dummy battery on the camera and the direct 12VDC plug on the VA. I did this also with a AB Gold Mount battery, using the DTap connectors, and a regulated E6 dummy battery connector on the Micro and the direct power plug in the VA, again no issues.

To be sure you do not short aHDMI or SDI connection, make all video cable connections first, before powering up the equipment, and power down before disconnecting the HDMI or SDI connection, and you should not have any problems. While HDMI claims "hot swaped plug and play" this does Not apply to high end video cameras and recorder/monitors
DS.

Alastair I agree with your repairman, HSMI failure not likely costed by your power setup, since you had the voltage regulated, which should have also isolated the two outputs, this is how a BDS works, it regulates and isolates the various outputs from the one common higher voltage battery. If the battery setup,was the issue, it would have blown right away.

Markus and Alastair, if you use a good Battery Distribution System (BDS) that regulates the power to 7.4 volts and isolates the two outputs, like the Atomos Power Station, which uses two Sony L batteries and distributes power to 2 isolated outputs at 7.4 (8.2 VDC max, which is a 7.2 battery max rating), and comes with two Cankn E6 dummy battery connectors. I use this with my Micro and VA setup, worked well if you used the large L batteries.

Nowhere in the marketing materials or manual for the Atomos Power Station does it claim that the two DC outputs are isolated from each other. That's actually extremely uncommon for most power sources; unless it's explicitly advertised I would *not* assume any DC output is isolated.

That said, I completely agree with your assessment that it's unlikely powering two cameras from the same ground would cause an HDMI port to die. There are so many other ways your equipment can/will share a ground as well - HDMI cable, XLR cable, etc.

To be sure you do not short aHDMI or SDI connection, make all video cable connections first, before powering up the equipment, and power down before disconnecting the HDMI or SDI connection, and you should not have any problems. While HDMI claims "hot swaped plug and play" this does Not apply to high end video cameras and recorder/monitors
DS.

Any camera or recorder that is damaged by hot swapping a video cable has a faulty design. I'm not saying it can't happen, but you can reasonably assume that to not be a problem.

True Quentin, the BMCC had an issue with hot swapping SDI cables on the video monitor output, which allowed a short if one was not real careful, so the recommendation was to power down Devices beforehand.

As the Atomos Power Ststion has a D.C. To D.C. Power converter, and after reading this comment by a reviewer:

An interesting option would be to pair the Power Station with a V-Mount or Gold Mount battery that has a D-Tap (P-Tap) power output. Using a D-Tap to 2.1mm adapter cable, the Power Station can add voltage-regulated power distribution to the battery, with enough input voltage that you shouldn't have any trouble powering your DSLR, monitor/recorder, and 5V USB device.

I made an assumption that the two 7.2/8.4 DC power output plugs both came off the power supply from separate taps, as the Power Station was marketed as a "Voltage Regulated Power Distribution System (BDS), thus "isolated" as they can detect a power overload and shut down the Power Station, which is how most BDS designs work. But I could me mistaken, and the two 7.2 volt taps could be both from the same tap on the power board, but the 7.2/8.4 plugs andmthr USB 5vdc plugs are isolated as they are different taps. Think I will take my Power Station apart to find out.
Cheers

True Quentin, the BMCC had an issue with hot swapping SDI cables on the video monitor output, which allowed a short if one was not real careful, so the recommendation was to power down Devices beforehand.

Yikes, that sucks. I hadn't heard about that design fault. Do you know if they ever made any hardware changes to fix the problem? A bit of Googling suggests that it might have been caused by a faulty SDI->HDMI converter people were using.

As the Atomos Power Ststion has a D.C. To D.C. Power converter, and after reading this comment by a reviewer:

An interesting option would be to pair the Power Station with a V-Mount or Gold Mount battery that has a D-Tap (P-Tap) power output. Using a D-Tap to 2.1mm adapter cable, the Power Station can add voltage-regulated power distribution to the battery, with enough input voltage that you shouldn't have any trouble powering your DSLR, monitor/recorder, and 5V USB device.

I made an assumption that the two 7.2/8.4 DC power output plugs both came off the power supply from separate taps, as the Oiwer Station was marketed as a "Voltage Regulated Power Distribution System (BDS), thus "isolated" as they can detect a power overload and shut down the Power Station, which is how most BDS designs work. But I could me mistaken, and the two 7.2 volt taps could be both from the same tap on the power board, but the 7.2/8.4 plugs andmthr USB 5vdc plugs are isolated as they are different taps. Think I will take my Power Station apart to find out.
Cheers

Aha! Just because there's a DC-DC converter does not mean the output's ground is isolated; many DC-DC converter topologies share a ground. Some even share a positive instead of a ground, but I wouldn't expect to find that in any camera equipment because it can easily cause major problems if you create a ground loop.

The easiest thing to do is to just take a multimeter set to continuity range and see if it beeps when you touch the ground of the two DC outputs. If it does, those outputs are not isolated. No need to take the power station apart.

Thanks Quentin, had the same thought after I wrote my previous post.

The ground issue was with the BMCC and hot swapping the SDI BNC connector when the camera and monitor were powered from a single source caused the SDI board to "fry". The power source was a knock off V Lock battery plate with supposed BDS outputs for 5, 7.4, and 12 VDC. This was several years ago, and when the Ursa Mini came out, the issue was redisscused, and given the lack,of experience with some new (to using SDI/BNC connections) users, the general advice was to power down the camera when making SDI connections.

In the TV studios I have worked with/at, ca eras were always connected first, the powered up. Same when setting up a remote with A Sony ENG camera, we ran the BNC cable from the truck to the camera first, then powered the camera up. Truck gear was already powered up, but camera not switched in until we had it ready to go.

Yes, with proper camera design of the HDMI and SDI boards, you should be able to hot swap, but since you do not always know what is "inside" a lot of these newer camera designs, best to play it safe -- Connect first, then power it up.
Cheers

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Thanks Denny and Quentin for the helpful discussion. I am pleased to think that the failure of my defunct HDMI out was probably not my fault.

I am now using a 4k Video Assist that I power from 2 NP-F970 batteries in series. I break the ~ 14.4 volt down to 12 volts using one of the regulators shown below. For around ten dollars on the internet you get this device that an output of up to 5 Amp. It can be set to cycle through readings of input voltage, output voltage, output current and output power. There is the option of displaying just one parameter or turning the display off completely. It is also possible to set a limit to the output current. The only strange feature is that the USB out voltage is the same as the other outlet. I have laboriously fitted a regulator (7805) to give a fixed 5V out at the USB outlet thus enabling me to set a different voltage at the other connection. The only drawback now is that the meter only shows the USB volts – to set the other I use a separate meter while making the adjustment. One use I have for the USB is an infrared extender.

The LANC control shown is the Prolanc, it comes with 3 built-in programs only one which works with the VA4k. On a suitable device the Prolanc has a number of functions, however on the VA it can only start or stop recording. It has a red LED that flashes continuously when the VA is powered. On other devices the flashing red indicates a problem.

Good, glad you got it sorted. Happy New Year.
Cheers

Cameras or recording that has been damaged by hot swap video cable has a design error. I'm not saying it can not happen. But you can reasonably conclude that it will not be a problem.

That LANC remote is exactly what I need: small and one-button triggering! Now the question is... where to find it and how much?

Nevermind, I just found the link and ordered one directly from prolanc!