Multi M1DBH's

[me2]

I would like to install a second M1DBH in a location away from the M1 Panel. The second m1dbh will 70 feet from the M1. The 1st m1dbh is in the box with the M1. I want to put the second one in the basement to free up some cable home runs.

Do I cable the 2 M1DBH's like the example "Daisy Chain Connections of Data Bus Devices Using Two Home Runs" on page 12 ?

Will this work?

ps: The first m1dbh is not full. I am not sure that I can use the crossover cable and J9 method.



edited to clear up my question

 

[Steve]

No, you need a crossover cable. You do it exactly like the diagram on the last page of the DBH manual.

Diagram for construction of a "Crossover" Cable using 8 Conductor Cat5 wire and 2 RJ45 Plugs.
Used for jumpering from connector J9 on 1 M1DBH to connector J1 on another M1DBH to extend the total
capacity of data bus connections.

 

[Spanky]

The second M1DBH should also be connected to the data bus that goes to the M1. Do not put a second M1DBH on a leg of the first M1DBH. If you do there could be too much time delay in the data direction switching.

 

[me2]

Now I am confused.

Steve are you saying I can use the crossover cable in J9 even though the 1st m1dbh is not full?

 

[Steve]

In the case of not filling up the first DBH I would have thought to put the crossover in the first unused position, then the terminator in the first unused position of the second. I would not think doing this would cause signal problems, but I would go with what Spanky says which I think is to simply homerun both DBH and connect them to the M1, which would give you 2 parallel branches.

 

[rfdesq]

Now what do you do when you have 3 DBH's?

 

[Steve]

Now what do you do when you have 3 DBH's?

Start drinking heavily?

Pray?

Ask Spanky?

Seriously, I know Spanky has always recommended no more than 2 branches off the controller, so I don't think he would say add a third there. I would think you could chain them all with the crossover as long as you did not approach the bus length limits???

 

[rfdesq]

I was kind of being facetious, but you caught my drift. I was instructed by Kurt years ago on a project I was working on to use the crossover cable method. Then add another branch for the other DBH's. The reason for the two branches was because of the physical locations of the DBH's from the M1 itself.

 

[bphillips]

Spanky mistook your question. His response has to do with the fact that you shouldn't daisy chain multiple M1DBHR <key letter being the "R". That is because an M1DBHR is an "active" hub (sort of similar but not exactly like an ethernet switch) and yes, if you try to daisy chain another M1DBHR off a leg of another M1DBHR it will delay the data bus signaling.

HOWEVER, the original question was about a standard M1DBH which is NOT an active device. It simply daisy chains the data path through each RJ45 plug.

Therefore it is OK to plug a second M1DBH into the last unused port of another M1DBH. Three (3) precautions: 1) The wire being used to feed the 2nd M1DBH must be wired as a crossover cable. See the instruction manual. 2) DO NOT EXCEED the combined max. data bus length of 4000 feet. Keep in mind that you will need to calculate each length of wire as "TWICE" its actual length since the data is going out to the device and then returning back to the M1DBH so it is therefore double its actual distance. 3) While it might be possible to feed a 3rd M1DBH off another, it probably shouldn't be done, simply because with each connection (plug) you are increasing the chance for high resistance or loose connections with each RJ45. Besides the fact that each length of wire is effectively double its actual length.