5vsb external power



  • So I was checking out the docs on external 5v, I recently converted my Davinci Pro 1.0 to a DuetWifi and PanelDue setup and am looking to power down the ATX supply by using the external 5v connection.

    I have searched high and low to a definitive answer on this. The wiki states that it can be powered by 5vsb. But then the image shows it needing ps_on.

    The power supply that comes in the Davinci is a 200W server 1u atx china power supply. It has 5vsb (green) and a black wire that goes to the on/off switch. With a black wire to the other side of the switch.

    Is it possible to wire this in a way to work as the external 5v or am I going to need an additional 5v supply.


  • administrators

    Yes you can use the 5VSB output from an ATX supply to power 5V and 3.3V circuits of the Duet, via the 5V external power input. The usual reason for doing this is so that the Duet's PS_ON output can turn the 12V power from the ATX supply on and off.



  • I get that, it does not appear to have a Ps_on wire… just the green VSB appears to switch to ground to turn the supply on.


  • administrators

    The PS_ON wire on your PSU is one of the wires that goes to the on/off switch.



  • Okay then the wikipedia article on this has me confused because it spoke of standby power, 5vsb and ps_on. It says that it turns the supply on by pulling 5vsb to ground.

    So based on what you say, because the green wire to my switch registers as 5vsb and the black wire to the switch has no voltage then the black wire is ps_on i would connect these to the Duet accordingly and then choose any ground wire from the supply to complete the Duets 3 connections?


  • administrators

    One of the black wires to the switch should have a small voltage on it when the button is off. The other one is ground.



  • @dc42:

    One of the black wires to the switch should have a small voltage on it when the button is off. The other one is ground.

    There is a single black wire to the switch which is ground and a green 5vsb wire to the switch. None of the other wires in the harness have voltage when the switch is off.




  • administrators

    The green wire connected to the switch doesn't go to 5VSB, it goes to the PS_ON connection in the power supply. 5VSB is a different pin that always provides 5V (at fairly low current) even when the power supply has not been turned on by the push button.



  • @dc42:

    The green wire connected to the switch doesn't go to 5VSB, it goes to the PS_ON connection in the power supply. 5VSB is a different pin that always provides 5V (at fairly low current) even when the power supply has not been turned on by the push button.

    I do not know then, the power supply clearly states that it has 2.0Amp +5Vsb the only wire that has 5V or any current for that matter is the green wire.


  • administrators

    The 5VSB wire is normally coloured purple.



  • Yeah i read that on the wikipedia, it just had me scratching my head because as you can see in the photo the psu states it has 5vsb

    I cracked the PSU open last night and 5vsb doesnt exist on the PCB everything is clearly labeled even the non used like -12v


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