@c310 said in Switching PSU on/off:

did you implement this?

Not yet, I am still doing the theory.

1. will this approach allow to start the printer with a push button ? (how long the push should be?)

Yes, there is a push button Normally Open on my diagram. As for the duration of the push, I don't know but it won't be long, I guess you could tell with the LEDs on the Duet or the relay when it is powered on.

2. would it be possible to switch printer off after print in automatic mode?

Of course, that's the whole point : just send M81 in your end Gcode and PS_ON will rise to high state (don't forget to adjust the logic accordingly on the relay module, usually via a jumper). This will turn the relay (hence the printer) off.

and for my understanding - why pushing ON button for a short while will keep printer ON ?

When everything is off, as the Duet board doesn't have any 5V input in this configuration, EXP1 doesn't supply 5V and PS_ON is not active. Which means that the relay is off. The push button is here to "jump start" the relay, by turning on the PSU, which will turn on the Duet, which will turn on the relay (assuming you added the M80 command in your config file). As soon as the relay is on, the push button is no longer needed to allow the L connection of the PSU. You can then release it.

@crynool said in Switching PSU on/off:

I assume he uses the M80 in the config.g file, a LED connected to an output could be used as indicator that it is safe to release the Button.

That's right, or use the existing LED as an indicator. I plan to connect a cooling fan for the Duet to the same 5V output as the one for the relay, so the fan starting up will be my signal to release the button.

The only thing I'm asking myself. The 5V on EXP1, where do they come from in case the PSU is switched off?
I want to be able to switch the PSU on via command OR Button. Is EXP1 powered with 5V even if the only connection to the Duet is via USB?
If this is not sufficient, an efficient 5V powersupply (USB Charger) connected to 5V input could solve the issue.

See my previous reply in this post. This method is meant to avoid the use of an external 5V power supply for the Duet, as I want to turn off the printer AND the Duet board when the print is finished. The drawback is that you have to start the printer using the push button. If you want to start the printer remotely, say via the web interface, then you need a 5V input for the board (like USB). This will indeed allow you to draw 5V on EXP1.

Ok, thank you for your original post and this reply, I will do this.

Hi there. Yet another post about using a relay to switch on and off the PSU with the Duet Wifi 2.0.

I did my homework, but I haven't found an actual wiring diagram. Throughout my research I've found the last post in this topic interesting :
Thoughts on powering on/off Duet remotely

Here is the wiring diagram of what I understood :

Is it correct ? The L switch is for disconnecting the relay from power when I'm not using my 3D printer. The push button is to start the printer. This would allow to use M80 and M81 in my gcodes without having to power the Duet via USB for example.

I plan to use this power module : https://www.banggood.com/5V-1-Channel-Level-Trigger-Optocoupler-Relay-Module-For-Arduino-p-915614.html?rmmds=detail-bottom-alsobought__3&cur_warehouse=CN

I know that PS_ON operates on low level so I will have to plug the jumper accordingly on the relay board.
It seems to have optocoupler isolation, but what about the "flyback diode across the relay coil" dc42 is talking about in his post ?

Thanks for your feedback and have a good day.