Blackmagic Forum

I'm working on building a multicore cable solution for my live event system based on a TVS. One of my ideas is to send camera and BMD converter power down the cable from a central power supply at the main rack.

I'm assuming if I have a power supply unit with enough juice to overcome the cable length attenuation any quality power supply will do. I have been considering this unit:

http://www.altronix.com/products/data_s ... 16ULCB.pdf

I thought I couls add a small home built circuit to drop the voltage to the 5VDC needed for the converters and the 12VDC needed for the cameras. I know the required output will be higher to compensate for cable runs but does my thinking make sense?

A nice patchbay for power on the rack would make life so much simpler.

Has anyone ever made up such a power supply system, and if so can you recommend units?

I want to power 4-6 Sony cameras with BMD converters.

Thanks

It has only 4Amp total output and at 15v that's only 60 Watts. And you want to power 4-6 cameras with converters? forget it.

I would recommend getting something like IDX IA-60A, which is single channel power supply, for each camera. You can fit a few of them in rack-mountable shelf or something. I wouldn't rely on CCTV stuff for quality DC power for my cameras.

If you have the skills and want to go DIY route, then computer power supply is number one choice. Much cheaper and more reliable then any CCTV power supply.

We recently had a vendor who had spec'ed out a system with the DC voltage down the spools ending up unable to do it. It just wasn't feasible with our Panasonic cameras. They were too picky about the incoming voltage. Not sure if your Sony cameras might have a similar issue.

They ended up putting regular 120VAC down the lines, and we use a camera power supply on the other end. No big deal, really. I just would prefer to not have 120VAC going down the spool. It works, and we are lucky enough to not have any power hum introduced into anything.

Remember, the cable loss on low voltage DC current is significant. The lower the voltage, and the longer the spool, the tougher it gets to do this. You'd need to use heavy 6 gauge wire or something similarly and obnoxiously thick to get a strong DC current down a 300 foot spool. The voltage will be there with small wire, but often, the current will not. I'm sure you could do some calculations on it, but you have to think of that spool as a big resistor in series with your camera - the smaller the wire, the higher the resistance. I'm not saying it can't be done, but I am saying it won't be easy, and you may not like the resulting weight of the cable. 100 foot spools, and you might have more luck, but it is still a challenge to the DC current.

If you custom make something on a spool with AC power, I do recommend using Neutrik Powercon connectors for it. It would help prevent any accidental misconnections if you used any other type of connector like XLRs or something. And Neutrik, as always, makes great connectors.

http://www.neutrik.com/en/industrial/po ... con-true1/

Also, consider going fiber instead, if you haven't already.

If you really want to avoid AC voltage down the line, and are having no luck at the low voltage, you could try a much higher DC voltage, like 24VDC or even better, 48VDC, and build a little circuit on the end of the spool to step the voltage down to where you need it. The higher the voltage, the less current you have to pull down it, the smaller your wire can be.

This is why the power companies distribute high voltage, like 110kilovolts, over major power power distribution lines, and step it down as needed. If they tried to deliver 120 VAC down major lines, they'd get no current or would have to use copper power lines 30 feet thick. It just doesn't work.


Most cable spools have loose cable ends with cable-end type connectors on them. But I used to make some with small, heavy-duty, die-cast aluminum boxes at the ends, with mounted connectors in them. Then I used short jumpers to connect my cameras and mics into the small box. With a design like that on your spool, you would have a little room inside the box for some small circuitry to step down 48VDC to your 12VDC and 5VDC and mount little power connectors for them. Just a thought.

Breakout boxes were like this: http://www.budind.com/view/Die+Cast+Alu ... e/Econobox

mrmaverick : we are maded 2U rack with power suplys , stabilizers , .. sending out 24V .. at camera there is stabilizer to 13.8V .. we are using cables from datavideo (intercom , power , SDI , ref) .. works great ..

Pytkin wrote:mrmaverick : we are maded 2U rack with power suplys , stabilizers , .. sending out 24V .. at camera there is stabilizer to 13.8V .. we are using cables from datavideo (intercom , power , SDI , ref) .. works great ..

What power supplies are you using? Can you give us a link?

Pytkin wrote:mrmaverick : we are maded 2U rack with power suplys , stabilizers , .. sending out 24V .. at camera there is stabilizer to 13.8V .. we are using cables from datavideo (intercom , power , SDI , ref) .. works great ..

Mmm, hmm. A real life application of what I said in many many words. And if your spools are real long, like 300', you might want 48VDC. How long are your camera lines, Pytkin?

pavel89 : im not sure .. but something like this : http://www.gme.sk/spinany-zdroj-mean-we ... 4-p751-396 .. there are 3 supplys in rack .. each supply is for 2 cameras ..

ssmith : yes U are right .. We are using 30m cables , whitch is stackable .. there are about -3V after one 30m cable .. max lenght we are using is 4x30m ... its tested and camera getting 13.8 V without problem ..

Please be very careful of AC line power down a multicore cable. I believe it is not only very dangerous, it is not allowed under electrical codes. The safe way is to use a proper low voltage power supply. Line voltage level drop will be an issue based on length and number of connectors. A 48 volt source going down the cables to a regulator at the camera end, should be a workable and safe solution. Meter the voltages at the camera/accessories with a full load--everything on and keep notes.

I recommend a single power supply for each camera/accessory group. Nothing is better than having a power supply die in production. Redundancy gives a better chance for success.
Good luck.

yes.. we wanted to put 3 supplys to use with redundacy .. but there was problem with distribution .. all load was from only one supply .. so we was divided it for single supply for 2 cameras .. better way will be two bigger supply (12A) and user it together for redundancy ..