URSA BROADCAST G2 powering from a distant power supply

We just upgraded our studio cameras from JVC GY-Hm790’s to the Blackmagic Ursa broadcast G2.

We have snakes that carry 12v 4 pin power from our control room to the studio. The snakes are approximately 100ft long. We had a multi port power distribution supply with 12v 60w 5Amp powering our old cameras with no issues. Due to the higher draw of the ursa G2, the existing power distribution doesn’t have a high enough amperage.

To overcome this, I have tried using the included blackmagic power supply plugged into the snake in the control room to no avail. I believe I am getting to much amperage loss on over the run. I’ve clarified that the pins are the same, and I checked the voltage on the camera side of the snake to see if there is a noticeable voltage drop. The voltage remains consistent and still 12 volts. I tried using a larger power supply with a higher amperage, but still no luck. According to the specs the camera requires 12v 8.33amps 100watts. I used a few online calculators to determine that based on the wire size I needed an input amperage of approximately 11amps to have 8.33 available at the output. I tried a 12v 12amp power supply on the control room side, but not luck. I still have 12 volts at the camera, but it still won’t power up.

Does anyone have any ideas on a possible solution? I know this is a long shot. Thanks in advance.

Your problem is not solved with a power supply that can deliver more amps, there is not really such a thing as "amperage loss". Instead, the voltage drop of a cable increases relative to the current drawn.

Try measuring the voltage when the camera is connected, not just when there is nothing drawing power.

If your wires are proper copper 1.5mm^2 (16AWG), 30ft each way (so total wire length including return current is 60ft), and you're drawing 8A, at 12V nominal voltage you'd only get about 8.5V. I'm guessing the camera also has some inrush current requirements when turning on and a minimum voltage level to turn on.

The "proper" way to solve this would be to have a 4-wire system, which would measure the voltage on the camera end with a separate pair of wires and raise the voltage accordingly. You might still need a more beefy power supply though, since a larger supply voltage and the same amperage equals more power.

A hack-ish way is to get a supply where you can tune the voltage with a trim pot or similar. The drawback is that you'd have a higher voltage on the line when nothing is connected / when you first connect the camera.

Every DC line loss calculator I've run shows 100% voltage drop with cables smaller than 18ga at 100 feet. You could have 100A 12V power supply but it's no good it it's only delivering 8V at the camera.

What's the gauge of the cable in the snake? Easy solution is to re-terminate the XLR with AC ends, or just reloom the snake with AC. According to the online calculators 12v DC @ 8A is a non starter until about 10 gauge which is heavy duty AC.

Good Luck

[Gary Adams]

Howard is correct as usual. As I've played with this a bit too, the startup current is the biggest problem causing the largest voltage drop initally. Once powered, the camera will probably run with smaller cable (assuming there is still at least 12V at the camera end based on the current. Some users will start up the camera locally either with supply or battery, then remove it once powered. This, of course is not ideal, but it gives you the idea of what is happening. Larger cable and possibly higher voltage supply, like 18 Volts may help. Or consider the SMPTE Camera Converter solution. I hope this helps.

Gary

I have the exact same problem, and it definitely comes down to inrush current. Running the original BMD 12V PSU over 30m of 2x2,5 sqmm will only drop the voltage at the camera by about 0,5V while it is running. It will refuse to start up though unless a charged V-Mount battery is attached, however once it runs I can remove the battery without problems.
I am wary of solving this by simply upping the voltage of the PSU. Depending on the current regulation system in the camera it may run a lot hotter on 18 or 20V. Additionally I consider running power supply systems close to their operating limits bad engineering practice.
I really think BMD should implement some kind of soft start/inrush current limiting here.

Ich habe eine BM Ursa Broadcast G2 über eine 100 Meter 2x LWL und 4-pol XLR Leitung (auf Trommel) extern mit Strom versorgen können. Diese Kabeltrommel war ursprünglich für die Studio Kamera konzipiert.
Das Vorgehen: als Einspeisenetzteil werden 24V 10A angelegt, an der Kamera kommt ein Spannungswandler 24V -> 12V 10A zum Einsatz. Das Bauteil ist an der Kamera montiert.
Dadurch ist es möglich, die Kamera extern über eine 100 Meter Leitung mit Strom zu versorgen.
Die Leistung an der Kamera reicht für den Kamerabetrieb, einen Studiomonitor, das Recording in der Kamera und hätte sogar noch Reserve für ein Kopflicht auf der Kamera mit halber Helligkeit.
Somit kann ich die Kamera mit nur einem Kabel über 100 Meter Entfernung mit 2 Signalwegen (In, Return Out) und Stromversorgung an der Regie anbinden und benötige keine zusätzliche externe Stromanbindung am Standort der Kamera.