Jump to content
jhartleycaw

Sharing - pole , 9 way 12v box

Recommended Posts

Evening all,

 

I have been given the unenviable task for refreshing some domes at work.

 

To save having to rewire, we are going to use the existing wiring, which is a BNC coax and a strange cable which seems to be 2 twisted pairs(or even 4 core) and a shield/ground. Looks to be slightly beefier than cat5 cores.

 

Each dome needs a 12v feed for the actual camera, and a 12v feed for the heater/fan, 750ma for the cam, and 1a for the heater/fan, as far as I can work out.

 

My idea was to run +- for the RS485 on 2 of the cores, and then +12v down each of the 2 remaining ones, sharing the - across 2 outputs off the 9 way with the shield/ground. 4 cams, use 8 of the outputs. 1 +12v feed for the cam, 1 for the heater. Or just twist 2 cores together, and split them at the other end.

 

Will this work, or a recipe for disaster? Not sure how bridging the - will affect the PTC fuses.

 

Backup plan is run cat5 to each camera, and triple up 6 of the cores for power and use the remaining 2 for signal, but as I said, want to avoid time in the ceiling chucking cable!

 

Thanks

 

James

Share this post


Link to post
Share on other sites

What is the maximum footage from the DVR and cameras? What is the size of 2 pair cable wires? If within the acceptable loss of DC, then just use 1 pair for the camera power and the other pair for the heater/fan.

 

If I understood what you were asking.

 

Dennis

Share this post


Link to post
Share on other sites

Hi, thanks for the reply, in answer to your questions:

 

DVR to each camera is max 10-15m

 

I'm not sure on the size of the cable, only that it is belden branded and has 4 cores and a shield.

 

I would give a pair for each, but I want to use one pair for signal(RS485) so only leaves 2 cores and the shield.

 

So basically wondering if I could use 1 core for power, 1 core for heater, and then share the shield between them. Effectively using 2 channels of the 9, 1 core to each plus and then split the shield to each minus. Would this blow the protection or share 2.2 amps between the feeds(assuming each channel is 1.1amp rated). I think I am assuming the minus is common across the 9 channels, which is more then likely wrong! It is one of those lockable boxes, with a 12v psu at the bottom and 9 fused channels.

 

Does that make sense?

 

Thanks again

 

James

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×