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#21886 - 06/19/10 06:08 PM ADNET Power Strategy
Cristian Adamo Offline
junior


Registered: 01/21/03
Posts: 27
Loc: Buenos Aires, Argentina
Hi there.

I am in the process of setting up an Adnet with one ocelot and 7 RlY8-XAs. There is a chance that all 56 relays might be ON at the same time. Some relays might be switching inductive loads but I have experience with that part of the problem.

I am worried about the power side of the installation, as I have had problems before with power and having several RLYs and relays turning off when you try to to turn too many relays on at the same time. Either power is not enough, or power cables cannot carry the load, etc.

So, for those who are savvy about the subject, help with the following questions would be greatly appreciated. My intention here is to get as reliable a system as possible from the beginning:

1) I am planning to power the entire Adnet with 12VDC. Any reason to go 9V instead of 12 or AC instead of DC?
2) I am not sure if I will be able to use one power supply for the entire ADNET. If I end up using 2 or three power supplies, is it still possible to have a common ground and if so how do you do that?
3) If I end-up using one power supply for the entire thing (12VDC@8A), what type of cable would you recommend I use for the two power cables? It would be safe to assume the entire length of the net will be about 150 feet.
4 Is it a good idea to terminate the bus, and if so, do I need to do this at both ends or only the one furthest away from the ocelot?

Thank you in advanced for sharing the knowledge...

Cris.-
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#21889 - 06/19/10 07:44 PM Re: ADNET Power Strategy [Re: Cristian Adamo]
ADI Tech Support Moderator Offline
addict


Registered: 12/22/02
Posts: 608
Loc: Branson West, MO
Chris

1) 9VDC. It helps keep the voltage regulators from overheating on the RLY8XAs.

2) It is not necessary to have a common ground.

3) I would go with about a 16 guage.

4) You generally do not have to terminate the bus. If you do, only terminate the end of the chain (the Ocelot is terminated).

Kevin Barrett
ADI Tech Support
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#21890 - 06/19/10 07:46 PM Re: ADNET Power Strategy [Re: Cristian Adamo]
Guy Lavoie Administrator Offline
Beyond All Hope
*****

Registered: 12/21/02
Posts: 6401
Loc: Montreal, QC, Canada
1) 12VDC is fine. No reason to go with anything else.

2) I don't know of a way to actually have a common ground among a bunch of RLY8XA's, unless you actually open the modules and connect to it's internal common (the 7805 regulator's metal tab maybe?). In that case, you would then connect your +12v to one of the PWR screw terminals, and leave the other PWR terminal unused.

3) #14 or #16 wire should be ok. Something like ordinary lamp cord should be fine.

4) you might want to terminate that the far end (end opposite the Ocelot). A 150 ohm resistor across the bus terminals would be good.
_________________________
"If you don't know what you're doing, do it neatly..."

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#21892 - 06/20/10 04:35 AM Re: ADNET Power Strategy [Re: Guy Lavoie]
Cristian Adamo Offline
junior


Registered: 01/21/03
Posts: 27
Loc: Buenos Aires, Argentina
Hi there... thank you for the quick replies... really helpful.

I am somewhat surprised by the fact that the common ground might not be a problem.

If you search for these terms in the forums, a lot of threads come-up and several comments about this having some sort of impact on data bus reliability. Guy even mentions this in the last entry for the following thread, and implies that DC power has the advantage to being able to establish a common ground:

http://www.appdigusers.com/forums/ubbthr...h=true#Post6770

I am not sure why this would be different in the scenario that I mentioned in this thread?

Thank you again! Just trying to learn here.... :-)
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#21893 - 06/20/10 12:35 PM Re: ADNET Power Strategy [Re: Cristian Adamo]
Guy Lavoie Administrator Offline
Beyond All Hope
*****

Registered: 12/21/02
Posts: 6401
Loc: Montreal, QC, Canada
I think that using a single power supply for the whole system will have a better effect on bus reliability then having a common ground. The usefulness of having a common ground is mainly in the case of using a SECU16 or 16I where you want to also power some signal devices that will be going to those module's inputs. In the case of the RLY8XA though, all outside connections are done to relay contacts that are isolated from any of the module's internal electronics.
_________________________
"If you don't know what you're doing, do it neatly..."

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#21894 - 06/20/10 07:57 PM Re: ADNET Power Strategy [Re: Guy Lavoie]
Cristian Adamo Offline
junior


Registered: 01/21/03
Posts: 27
Loc: Buenos Aires, Argentina
Guy... thank you so much.
I will then try to use one power supply if possible at all. I might add a secu-16 or secu16-i down the line at some point...

Cristian.-
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#21896 - 06/21/10 06:27 PM Re: ADNET Power Strategy [Re: Cristian Adamo]
Cristian Adamo Offline
junior


Registered: 01/21/03
Posts: 27
Loc: Buenos Aires, Argentina
Would something like this work if I want to do this with one power supply? I guess 9vdc@16A should be more than enough even in case I want to add additional modules down the road...

http://www.mouser.com/ProductDetail/Mean...jliLBcDOiotU%3d

Thanks!
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#21898 - 06/21/10 08:37 PM Re: ADNET Power Strategy [Re: Cristian Adamo]
Guy Lavoie Administrator Offline
Beyond All Hope
*****

Registered: 12/21/02
Posts: 6401
Loc: Montreal, QC, Canada
9 volts is right on the edge. It might work ok for RLY8XA's as Kevin mentioned (it does help to reduce internal heat), but not sure about some other modules, like a SpeakEZ. But it looks like a good fit for what you want to do.
_________________________
"If you don't know what you're doing, do it neatly..."

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#21905 - 06/23/10 06:50 AM Re: ADNET Power Strategy [Re: Guy Lavoie]
Cristian Adamo Offline
junior


Registered: 01/21/03
Posts: 27
Loc: Buenos Aires, Argentina
Thanks!
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