12VDC vs' 24VAC

[MrSquid 0]

I just finished setting up two Sony D/N Dome camera's and a b/w bullet connected to a 1240 GeoVision system. Right now I am using a 12VDC powersupply. I have 16/2 pulled along with rg-59 to each camera. Is there any advantage to using a 24VAC powersupply instead?

 

Thanks,

Anthony

[griffonsystems 0]

a lot of outdoor housing only use 24vac so for those i always run ac.

[MrSquid 0]

Is there any difference in picture quality?

 

Would I need a 3rd wire to ground the housing with A/C?

[securitymonster 0]

you can get a longer run with 24V AC

[griffonsystems 0]

picture quality is with the camera and the lens not the power used, but if you are looking at a run over 500ft prob wise to go with 24vac

 

no you dont need a 3rd wire to ground ac - at least i have never needed one

[rory 0]

24VAC is also better for indoors with florecent lighting.

[Cooperman 0]

In theory, there used to be an advantage in using 24v AC, simply because "line locked" cameras would use the 50 or 60 Hz waveform as a reference to trigger the image capture; so if they were all on the same supply, they would all trigger at the same point, and that would make it easier for recorders and multiplexers to lock on to their video signals.

 

In practice, modern recording and display equipment is so much more stable, there is little technical advantage now in using 24v AC over 12v DC.

 

24v AC can certainly be run further than 12v DC, but as an earth conductor is normally required (certainly this side of the water), it is much more prone to earth loop problems than 12v cameras which are not generally grounded.

 

Also, it's often easier and cheaper to provide a battery 'back up' for 12v cameras.

[rory 0]

dont use "earth" (ground?) on this side of the globe ..

[normicgander 0]

The old Edison vs. Westinghouse battle again...

 

Ohms Law wins.

 

I agree with giffonsystems, its more of an efficiency issue. 12Vdc is fine for short runs...

[MrSquid 0]

Thanks everyone. My runs are all less then 100' so it looks like I will stick with the 12vdc that I have.

[GECAMGUY 0]

I'm no installer and certainly don't have the breadth of experience those that have posted on here have mentioned but just to throw my two BNC connectors into this.

 

In our lab, one thing I've noticed about cameras that are 12VDC/24VAC is if I run 12VDC and I don't switch the camera from Line Lock to internal lock, I often see color rolling between Green and Blue. This isn't just with GE cameras, I see it happen with competing cameras as well. I've even seen cameras that state that their universal 12VDC/24VAC but have it factory set to Line Lock with no way to change it so, yeah you can run 12VDC, but you get lousy video.

 

That being said, I generallly recommend 12VDC for anything under about 100', but not longer than that unless you're also using the wiring to heat your building as well as power the camera

 

Oh one other thing, if your powering a camera that you may some day switch out to an IP camera, most IP cameras are 12VDC only, so keep that in mind as you "Futureproof" your installation.