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ELK-M1XIN Does it have to be powered from the bus?

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#1 auzzzie



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Posted 05 September 2018 - 11:39 PM

Can I power the ELK-M1XIN (Input Expander) from an external power supply or does it have to be from the RS485 Data Bus?


Reason being, I have a remote unit in the garage and only a single CAT5E between the buildings. I want to use some of the pairs for other things as  I have a 12+ PSU local to the input expander so it seems like a waste to pull power from the other building. 



#2 RAL



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Posted 06 September 2018 - 12:30 PM

The M1XIN can be powered from an aux power supply.  In theory, the RS485 bus can work with just the two Data A and Data B signals between the M1 and the XIN.  But in practice, you may find that you need a common ground (NEG) signal between the two for it to work reliably.  Without a common ground, the two power supplies can have a difference in what each sees as the 0 volt signal level (i.e. a different ground reference).  If they get too far apart, the RS485 receivers can't detect the signals properly.

#3 mikefamig



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Posted 07 September 2018 - 11:21 AM

I recommend getting a power supply with adjustable output voltage. That will allow you to tweak it a little if needed to overcome a long wire run and match it close to the supply on the M1.



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