Joining two dvrs together to use same rs485

[typnar 0]

I have two DVRs and want to use a single rs485 cable.

 

Both dvrs are next to each other.

 

I could just tap into the existing wire but I feel resistors or other things might be needed to have this operate properly.

[SEANHAWG 1]

What one device are you using that would needed to be controlled by 2 DVR's?

 

Or better yet, what exactly are you trying to do?

[typnar 0]

It's not one device used by two dvrs I just want to use the same rs485 cable with different camera id.

 

I have multiple zoom box cameras running on a second floor with 1 wire already ran.

 

here is a outline of what I'm trying to do.

So the extra 2 cameras at the top right are next to each other and can just link off one of the existing ones.

[tomcctv 190]

either use a controller next to your dvrs or if your system has a CMS software that will give you all cameras with control. what make are your DVRs.

 

to set it up as your diagram will not help as you would still need to log into the DVR to see the camera you want to control.

[typnar 0]

I don't have a controller, these are two Mace brand DVRs and I'm using the Mace Software to control them.

They are all connected.

The issue is having to run duplicate cat5 rs485 to control a cameras on a different dvr right next to each other.

 

Isn't there some kind of a resistor or isolator I add to the rs485 line so it doesn't send the signal back into each dvr?

[tomcctv 190]

I don't have a controller, these are two Mace brand DVRs and I'm using the Mace Software to control them.

They are all connected.

The issue is having to run duplicate cat5 rs485 to control a cameras on a different dvr right next to each other.

 

 

 

 

hi. you would still not get control from another dvr.

 

DVR 1 you set up your settings for control of the camera... so as when you click on the camera you can use the onboad controller to zoom.

 

so if you then move to DVR 2 and you want to control the same camera you cant it is not in the DVR settings. 485 is out only (transmit)

 

so you have 2 DVRs and 2 monitors. you can do it with the mace but you would need to go 2 DVRs to PC with monitor and use mace CMS.

[Soundy 1]

Something like this should work: http://www.485solutions.com/product_family.asp?familyid=31

 

It's actually a pretty simple design - the datasheet for it has a full schematic: http://www.485solutions.com/bb-elec/literature/9pmds-3803ds.pdf

[typnar 0]

I am not trying to have either DVR be able to control any camera. Each DVR will still handle their own cameras, I'm only trying to share the single wire.

 

Here is a new image to show the way I want it to end up.

 

Also note, by RS485 cable I mean the two + - wire A & B.

 

You will see I want to extend the current wire to cover the extra cameras that were previously attached to another wire.

 

I do know that just attaching it as shown will work but the problem I don't want to happen is the signal gets caught in a loop or the signal gets sent backwards into the dvr.

For that is why I'm needing some sort of resistor or isolator to add into the beginning of each DVRS cable so it does not accept a signal backwards.

 

[Soundy 1]

For that, you don't need to do anything special. If the two DVRs are side-by-side and the wires for those cameras are right there, just disconnect from the one DVR and tie them into the other. Whether you star them out or daisy-chain them, the whole thing is just one parallel circuit... just make sure if you're daisy-chaining (as shown on your second diagram) that the camera at the end of the chain has termination enabled, and the ones "below" it on that chain don't.

[tomcctv 190]

hi. you are controlling the cameras from your dvr software which is fine but on your diagram you still have the 485 connecting both (you cant)

 

 

your diagram shows DVR 1 controlling 1 camera .... DVR 2 controlling 5 cameras and with the 485 link back to DVR 1 from DVR 2 why do you need this ???

[typnar 0]

For that, you don't need to do anything special. If the two DVRs are side-by-side and the wires for those cameras are right there, just disconnect from the one DVR and tie them into the other. Whether you star them out or daisy-chain them, the whole thing is just one parallel circuit... just make sure if you're daisy-chaining (as shown on your second diagram) that the camera at the end of the chain has termination enabled, and the ones "below" it on that chain don't.

Yes it will be daisy-chaining.

your diagram shows DVR 1 controlling 1 camera .... DVR 2 controlling 5 cameras and with the 485 link back to DVR 1 from DVR 2 why do you need this ???

I'm using more cameras than my diagrams show and this will give you a better idea.

DVR A goes with cameras A# then DVR B control B# cameras.

 

 

I want the current to flow the way of the green arrows and not back into each others DVR with termination at A-2.

I just figured it out, it's a diode that controls or blocks the flow of current to just go in one direction.

So adding a diode into the A & B wires just after they leaves the DVR would prevent DVR-A's signal from going into DVR-B and vise versa.

 

The whole purpose of this is to prevent any damage from stray signals going back into the dvrs.

 

Is this something that anyone has experience with using?

( ±80V Fault-Protected, Fail-Safe, 1/4-Unit Load, +3.3V RS-485 Transceiver )

http://www.futurlec.com/Maxim/MAX3430CSApr.shtml

[treborsz 0]

The serial data distributor gives serial data from multiple inputs on multiple outputs at the same time. All inputs can be "stand by" status at the same time, but only one controller/DVR will be activated at once.

[tomcctv 190]

I just figured it out, it's a diode that controls or blocks the flow of current to just go in one direction.

 

 

that will just give you problems. what about end of line termination ???

 

just buy a roll of cat5 link camera A1 to A2 and A3 and drop the link from A3 to B1 and the data link to each dvr. job done.

 

if getting cables to the camera is a problem then just ADD a controller if both DVRs are next to each other that may be your best way

[Soundy 1]

So adding a diode into the A & B wires just after they leaves the DVR would prevent DVR-A's signal from going into DVR-B and vise versa

So will simply removing the wire connecting the two - you've already stated you don't need each DVR to control the other DVR's cameras so there's no reason for that connection to be there.

 

The whole purpose of this is to prevent any damage from stray signals going back into the dvrs.

You can't damage anything this way - at worst you might have cameras being confused or signal being dampened.