Dual DC in on mini

Technical discussions about our hardware electronics with our product engineer.
User avatar
4000ft
Member
 
Posts: 5
Joined: Thu Nov 02, 2017 12:07 am
Has thanked: 1 time
Been thanked: 0 time

Dual DC in on mini

Fri Nov 03, 2017 11:01 pm

What happen if we connect two independent DC inputs to the mini's barell connector and POE in.
Which one will power the device and what is the logistic behind it.

We have several Mtik powerbox pro's and we power them with two independent dc inputs, barrell and POE in.
The powerbox takes the input with higher voltage. Works great as a redundant power, however there is no way to find out which one of the ports is currently on, nor the incoming current.

Cheers, Pavel

Julian
 

Re: Dual DC in on mini

Mon Nov 06, 2017 10:43 am

DC power in is protected by a single flyback diode, and both polarities use wired-AND logic with the outputs of the POE input's bridge rectifiers.

Powering via both at once is not a recommended method. I can, however, tell you that I've tried it briefly in the lab without breaking anything,

User avatar
lligetfa
Associate
Associate
 
Posts: 1191
Joined: Sun Aug 03, 2014 12:12 pm
Location: Fort Frances Ont. Canada
Has thanked: 306 times
Been thanked: 381 times

Re: Dual DC in on mini

Mon Nov 06, 2017 1:12 pm

I wanted very much to do this. I have a MINI out in a storage shelter that does not have reliable AC mains power but it does have PoE via a 300 foot buried CAT5 run. The long run has a voltage drop at high wattage that was alerting on low voltage for the 48V kit. I could power it with a brick from local AC power but as it is unreliable, would want the PoE power as a backup. I asked Dave if I could use both PoE and barrel at the same time but he would not endorse it and did not give a reason.

User avatar
sirhc
Employee
Employee
 
Posts: 7398
Joined: Tue Apr 08, 2014 3:48 pm
Location: Lancaster, PA
Has thanked: 1604 times
Been thanked: 1322 times

Re: Dual DC in on mini

Mon Nov 06, 2017 1:48 pm

So the official answer is NOT RECOMMENDED, not responsible for damage of any kind resulting from this.
Support is handled on the Forums not in Emails and PMs.
Before you ask a question use the Search function to see it has been answered before.
To do an Advanced Search click the magnifying glass in the Search Box.
To upload pictures click the Upload attachment link below the BLUE SUBMIT BUTTON.

Julian
 

Re: Dual DC in on mini

Mon Nov 06, 2017 2:56 pm

I think the reason is that if POE DC+ in were to become sufficiently more positive with respect to DC+ in (barrel connector) for any reason, sparks can and will emit from your device and could possibly render it nonfunctional.. Just a theory, though, I may do some testing later in the week on this.

Dave will probably have input once he gets his crazy canadian internet working.

User avatar
sirhc
Employee
Employee
 
Posts: 7398
Joined: Tue Apr 08, 2014 3:48 pm
Location: Lancaster, PA
Has thanked: 1604 times
Been thanked: 1322 times

Re: Dual DC in on mini

Mon Nov 06, 2017 2:59 pm

This is not recommended as you are bonding 2 separate DC power sources together and there is no protection circuits in place to protect each power source from the other.

In units that have redundant power supplies there are circuits between the power sources to prevent them from affecting each other and in the event something happens to one that it does not short out and the other power supply heats things up and POOF or worse.
Support is handled on the Forums not in Emails and PMs.
Before you ask a question use the Search function to see it has been answered before.
To do an Advanced Search click the magnifying glass in the Search Box.
To upload pictures click the Upload attachment link below the BLUE SUBMIT BUTTON.

uberdome
Experienced Member
 
Posts: 127
Joined: Thu Sep 08, 2016 6:58 am
Has thanked: 3 times
Been thanked: 11 times

Re: Dual DC in on mini

Mon May 03, 2021 6:38 pm

The WS-6-MINI remains one of my favorite small switches for microPoPs.

If you are doing a design revision on this product, it would be very useful to allow dual power input like the MikroTik products do (I think they have a rectifier on both inputs). I have to repair a line feeding a WS-6-MINI this week, and if I could plug it in to a second power source, I could keep it powered and rely on secondary network paths so no customers go down. I connected a secondary power on a MikroTik this past week for re-working a power supply, and it kept everything working while I repaired a system.

Thank you, Chris

Return to Dave's Lab

Who is online

Users browsing this forum: No registered users and 19 guests