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A couple of Multicam doubts and general help

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Re: A couple of Multicam doubts and general help
« Reply #70 on: 03 / December / 2019, 12:42:57 »
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Ok, I won't be touching that then! I wonder what waterwingz meant with "problems with grounding" on #41, and on the last bit of #45... :blink:


BTW I'm not planning to change the shooting procedure, it's perfect as it is now. The whole 3rd cable idea comes from #41, was he referring to another type of grounding problems?
« Last Edit: 03 / December / 2019, 12:45:07 by ikercito »

Re: A couple of Multicam doubts and general help
« Reply #71 on: 03 / December / 2019, 13:15:07 »
Ok, I won't be touching that then! I wonder what waterwingz meant with "problems with grounding" on #41, and on the last bit of #45...
Grounding problems can occur with multi-camera rigs primarily because of all the different AC to DC power supplies being used for the USB hubs and "battery eliminators"

In theory, each of those power supply provides a 100% floating DC output.   The issue comes when those different outputs are only randomly connected together through a maze of small ground paths through he USB trigger cables and "dummy battery" connectors.  This can creates voltage offsets and current spikes that cause weird random problem - possibly including camera crashes.  And with some power supplies, the isolation is not perfect to the mains (or AC) side of the power supply, allowing potential shock hazards (one CHDK multicam user reported just that several years ago).

So, the best way to handle this is to use a heavy gauge wire (say 14 ga.) to interconnect the DC grounds of each of the power supplies for the cameras and the USB hubs. People tend not to do this as it's extra work and the little "wall wart" power packs for the USB hubs and the battery eliminator power supplies tend not to provide a convenient connection point.  But even if you can't connect all of the power supply grounds, interconnecting the 0V wires coming from each dummy battery power pack is a pretty good compromise as that's where the most substantial current flows will be.  You don't need a wire to the dummy battery itself as it's better to just connect things at the power supply end.  To finish this off, you can connect (bond) that common ground conductor to building ground ("earth") for a bit of added protection.

Does that help?


 
Ported :   A1200    SD940   G10    Powershot N    G16

Re: A couple of Multicam doubts and general help
« Reply #72 on: 03 / December / 2019, 13:34:17 »

It does! Thank you so much for clarifying! Tomorrow I'll check what can be done about it.


interconnecting the 0V wires coming from each dummy battery power pack
All the power strips are grounded to building ground. The power supplies for dummies are grounded individually too. The SX150 battery adapters do not seem to have any grounding (will check tomorrow, I'm out of the studio now) Should I interconnect the ground between them? Never thought that would be safe... But again I have no f*** clue of what I'm talking about. Thanks so much for your patience :)

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Re: A couple of Multicam doubts and general help
« Reply #73 on: 03 / December / 2019, 13:48:15 »
Generally, how to optimize a smooth start of the rig?  :-*
I would power up each 'tripod' one by one with some secs delay to avoid heavy power peeks.
Then boot computer...
All lifetime is a loan from eternity.


Re: A couple of Multicam doubts and general help
« Reply #74 on: 03 / December / 2019, 13:51:48 »
All the power strips are grounded to building ground.
That's good  (and almost certainly required by your local electrical code).

However, remember that each of your power supplies can be thought of as having two sides.  One side is connected to the AC mains power..  The other side connects DC low voltage power to your cameras.  Inside the power supply, the electronics magic converts the high voltage AC mains power into safe low voltage DC power. There is no actual electrical connection between the two sides though - they are "isolated" (or supposed to be).

So connecting things to building ground on the AC side does nothing to create a common ground on the DC side.

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The power supplies for dummies are grounded individually too.
I assume you mean on the AC side? See my previous comment if so.

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The SX150 battery adapters do not seem to have any grounding (will check tomorrow, I'm out of the studio now)
AC side again?  This is not uncommon and allowed by electrical code if the internal design meets a "double insulated" standard.

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Should I interconnect the ground between them?
Don't touch anything on the main/AC/high voltage side.  Please.

On the DC side, where the + and - cables we discussed earlier come out, you should interconnect a single thick conductor (at least 18ga and 14ga even better) between each of the black ( - ) negative wires as close to each power supply as possible.  Tie the end of that wire to building earth (ground) for extra protection.

Ported :   A1200    SD940   G10    Powershot N    G16

Re: A couple of Multicam doubts and general help
« Reply #75 on: 03 / December / 2019, 14:08:43 »
Will check it out tomorrow, but here's a drawing to check if I understood correctly. (Note: red cables are untouched)

Re: A couple of Multicam doubts and general help
« Reply #76 on: 03 / December / 2019, 14:17:36 »
Generally, how to optimize a smooth start of the rig?  :-*
I would power up each 'tripod' one by one with some secs delay to avoid heavy power peeks.  Then boot computer...
While I'm not sure that's completely necessary,  there is certainly nothing wrong with doing it that way.
Ported :   A1200    SD940   G10    Powershot N    G16

Re: A couple of Multicam doubts and general help
« Reply #77 on: 03 / December / 2019, 15:09:07 »
Will check it out tomorrow, but here's a drawing to check if I understood correctly. (Note: red cables are untouched)
Good - you've got the concept now.  I expanded it a bit for you - note that AC mains wires are a different color too. Safety first!

« Last Edit: 03 / December / 2019, 17:18:47 by waterwingz »
Ported :   A1200    SD940   G10    Powershot N    G16


Re: A couple of Multicam doubts and general help
« Reply #78 on: 04 / December / 2019, 07:53:51 »
Today I received the power sources I mentioned: 5V 10A 50W, brand new.. I connected the mains cabling and measured with the voltmeter. At first it was giving around 5.3V so I turned it down to the minimum, and it was around 4.6V. I checked the cameras and at the bottom it says 4.3V so thought the cameras could well withstand a little bit more tension and proceeded to plug one of them
Incidentally, there is an old trick you could use here to lower the voltage output a little bit more.  Install a 5A silicon diode in series with the +5V output of each of these power supplies. Or a seperate 2A diode to each camera. At the current level you will be using it shoild give you a constant 0.5 to 0.6V voltage drop - enough to get to the specified operating voltage of the camera.
« Last Edit: 04 / December / 2019, 09:15:52 by waterwingz »
Ported :   A1200    SD940   G10    Powershot N    G16

Re: A couple of Multicam doubts and general help
« Reply #79 on: 04 / December / 2019, 10:28:42 »
Something like this... Or a 2A on each of the cameras, instead.


In any case, I may temporarily leave this out.  There's 0,5V excess, as long as the power source can keep up with it, the cameras should be fine right?


 

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