Inverting PS_ON levels



  • I recently upgraded to a Meanwell 24V PSU and it's finally time to wire up the remote on/off feature of the Duet/PSU. Sadly the PSU operates at inverted logic levels compared to the Duet PS_ON terminal.
    My idea was to take the PS_ON signal and hook it up to a RPi Zero W that I already have streaming a video. With the RPi I want to invert the signal and wire it to the PSU RC+. The RC- terminal would be wired to ground.

    Is this a valid way to do this?



  • Keep in mind that the GPIO pins are 3.3v, however, it does sound a little complex just for inverting a signal.

    I have a Meanwell supply with an optocoupler and a couple of resistors to invert PS_ON.
    If you're handy with a soldering iron it's another possible solution.



  • I've recently wired up one of those PSUs with an inline logic inverter, which I had from a radio control plane, connected to the PS_ON. I reckon your plan should work. The rpi will need to connect the RC+ on the PSU to ground/RC- to turn off the PSU. RC+ can float open circuit or be connected to the +5v standby to enable the PSU. The PSU labelling is confusing, but think of RC+ as the signal wire to switch, RC- as ground, and +5v as +5v. The only problem I can think of is that the standby 5v only supplies 500mA - that might not be enough to power the duet and rpi....



  • @insertnamehere said in Inverting PS_ON levels:

    I have a Meanwell supply with an optocoupler and a couple of resistors to invert PS_ON.
    If you're handy with a soldering iron it's another possible solution.

    Soldering is not an issue, how did you make a resistor based inverter?

    @pawprinter said in Inverting PS_ON levels:

    I've recently wired up one of those PSUs with an inline logic inverter, which I had from a radio control plane, connected to the PS_ON. I reckon your plan should work. The rpi will need to connect the RC+ on the PSU to ground/RC- to turn off the PSU. RC+ can float open circuit or be connected to the +5v standby to enable the PSU. The PSU labelling is confusing, but think of RC+ as the signal wire to switch, RC- as ground, and +5v as +5v. The only problem I can think of is that the standby 5v only supplies 500mA - that might not be enough to power the duet and rpi....

    I have a separate 5V PSU wired, so that will be a non issue.



  • @nxt-1 +5V is from the Meanwell aux supply.
    0_1549362828552_schemeit-project-2.png



  • @insertnamehere are the 5V @ 500mA (says 300mA in the datasheet) enough to power the Duet reliably?



  • @devleon In the OPs case possibly not. I'm using a Meanwell HFG600 which is 5V @ 500mA in the spec.
    I don't have a panelDue attached and fans all run off the 24V.
    I've seen no problems using a 500mA supply over 100s of hours printing.


 

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