Noob help for RS 485 3 wire connection to cat. 5E please.

[kingdommaker 0]

Hello all, I cannot figure out how to connect an orange, yellow and yellow/green wire RS 485 from an ASH-56NVIR camera to Cat. 5E to connect to an AU40Z PTZ controller. The camera manual says to connect colors of wire but they don't match.

 

Any quick links for your ease would be greatly appreciated.

Edited July 7, 2009 by Guest

[Soundy 1]

Are these wires labeled? With RS485, you'd normally use RX+ and RX- on the camera, connected to TX+ and TX- (respectively) on the controller (a few cameras I've seen label the RX pins as TX, I assume to tell you what to connect them to rather than their actual function). TX on the camera should not normally be required.

 

Remember that once you're connected, you have to set your controller (joystick, DVR, whatever) to the proper port settings (baud rate, parity, etc.), and your software to the same protocol (Pelco D or P or whatever else is supported) and tell it the ID number of the camera.

 

With many cameras, the port, protocol, and ID info is displayed when the camera boots up...

[kingdommaker 0]

Yes, the 2 wires are labeled thanks. However should I connect the ground wire to R+ or R-?

[Soundy 1]

Um, what ground wire? On the camera, or the controller?

 

Ground should not be required - TX+ on the controller goes to RX+ on the camera; TX- goes to RX-. That should be all it takes. Only one pair of the Cat5 is used.

[kingdommaker 0]

The camera has a yellow striped green ground wire in the rs 485 connector cable.

 

I read an article on grounding rs 485 it but this site won't let me post links for 5 days...

[Soundy 1]

That ground should not be required. It might be useful if there's noise in the picture or other issues, but RS485 doesn't REQUIRE it.

[Sawbones 0]

Soundy is correct; don't worry about the ground wire. RS 485 is a two-wire connection.

[kingdommaker 0]

Interesting. Here is another 3 wire rs 485.

 

***.coleparmer.***/catalog/product_view.asp?sku=8982056

[TastyHuman 0]

Soundy is correct; don't worry about the ground wire. RS 485 is a two-wire connection.

 

The RS-485 standard is a three wire connection. It's a differential pair but each signal pin is referenced to ground. Now whether the manufacturer understood this or not is another matter. Failure to reference these pins to ground can potentially cause big problems for when the signal goes out of the valid +/- range the transceiver chip can overheat and kick in the protection circuitry to shut it down (best case) or burnout the part completely (worst case).

 

But you don't have to believe me. Here's a link:

 

http://www.chipkin.com/articles/rs485-cables-why-you-need-3-wires-for-2-two-wire-rs485

 

Any device that implemented two wire rs-485 is designed incorrectly. Yes, it will generally work fine on short runs but for longer runs with different ground potentials at the drops trouble can bite you.