Are fans powered if PS_ON is off?



  • My machine is powered my a 24V PSU and a separate 5V PSU to allow for remote PS_ON/OFF'ing. My fans are all 12V, so I installed a cheap Chinese buck-converter from the 24V rail to V_FAN. I want to replace this buck-converter small dedicated 12V PSU that is always on. My question is whether this will leave the fans always powered on no matter the state of PS_ON?



  • @nxt-1 said in Are fans powered if PS_ON is off?:

    My machine is powered my a 24V PSU and a separate 5V PSU to allow for remote PS_ON/OFF'ing. My fans are all 12V, so I installed a cheap Chinese buck-converter from the 24V rail to V_FAN. I want to replace this buck-converter small dedicated 12V PSU that is always on. My question is whether this will leave the fans always powered on no matter the state of PS_ON?

    Yes it will. PS_ON is only an external signal. If you don't control the 12v PSU with it then the fans will stay on.



  • Surely fans connected to the fan ouputs on the duet would not stay on unless told by the firmware to stay on, the 12v psu and any fans directly connected to the 12v psu would be on regardless of ps_on signal.

    For the latter you'd need to use the ps_on signal or 24v supply to control the 12v psu as well.



  • @bearer said in Are fans powered if PS_ON is off?:

    Surely fans connected to the fan ouputs on the duet would not stay on unless told by the firmware to stay on, the 12v psu and any fans directly connected to the 12v psu would be on regardless of ps_on signal.

    For the latter you'd need to use the ps_on signal or 24v supply to control the 12v psu as well.

    Yeah, of course. If you haven't actually turned on the fan with gcode ps_on won't matter 🙂



  • @bearer said in Are fans powered if PS_ON is off?:

    Surely fans connected to the fan ouputs on the duet would not stay on unless told by the firmware to stay on, the 12v psu and any fans directly connected to the 12v psu would be on regardless of ps_on signal.

    For the latter you'd need to use the ps_on signal or 24v supply to control the 12v psu as well.

    The controllable fans are a non issue as the are usually off when the printer is turned off. But the always on fans should remain off for a long as the Duet is in 'off' mode imo. Maybe it should be an option in the config whether M80/M81 influences the fans as well. @dc42


  • administrators

    @nxt-1 said in Are fans powered if PS_ON is off?:

    The controllable fans are a non issue as the are usually off when the printer is turned off. But the always on fans should remain off for a long as the Duet is in 'off' mode imo. Maybe it should be an option in the config whether M80/M81 influences the fans as well. @dc42

    The always-on fans are as it says, always-on as long a VFAN power is provided. The firmware can't control them.



  • @dc42 said in Are fans powered if PS_ON is off?:

    @nxt-1 said in Are fans powered if PS_ON is off?:

    The controllable fans are a non issue as the are usually off when the printer is turned off. But the always on fans should remain off for a long as the Duet is in 'off' mode imo. Maybe it should be an option in the config whether M80/M81 influences the fans as well. @dc42

    The always-on fans are as it says, always-on as long a VFAN power is provided. The firmware can't control them.

    Ah, I assumed the always on fans were in fact connected to the MCU in some way. Thanks for clearing that up, I will have to look in to controlling the 12V PSU then.


 

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