SKR V1.3 ATX PSU


Learn how to turn your 3D printer on and off again in Marlin 2.0 with the SKR V1.3 and an ATX PSU. Follow our guide and get to grips with PS_ON.

Being able to turn on and off the ATX PSU via the SKR V1.3 is a very handy function. Especially when it comes to that extra bit of safety. Moreover, the ability for the printer to self shutdown completely on receiving a thermal runaway is priceless.

Parts List

Wires Cutters, Wire Strippers, 2.54mm JST-SM Connectors, 2.54mm JST-XHP Connectors, 16 AWG Silicone Cable.

ATX Breakout, while not necessary it does makes life a lot easier.
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Wiring the Relay

There are two ways we can set up the PS_ON switch, firstly as an emergency shut down, and kill all power. Secondly would be to have it shut down the main power and only leave 5 volts standby power remaining. Consequentially enabling the SKR V1.3 to still be available for firmware updates.

First, to make this easier to follow along I have broken it down into sections. However you will need the parts in the above list.

ATX to Relay

STEP 1

The first step is to make up some cable with the 26 AWG Silicone wiring. We will require two lengths red and black, that will reach from your ATX PSU to the point you have placed your relay.

The wiring needs to have Dupont connectors on one end and bare wire on the other.

  • Connect the red wire Dupont’s connector to the pin on the Relay marked VCC and screw the other end into the ATX breakout board marked +5VSB.
  • Similarly, the black wire the Dupont connector goes into the pin marked GND on the Relay board.

Now at this point the relay now gets power from the ATX PSU, but no switch method, and it goes to nowhere.

STEP 2

For the second step again we need some 26 AWG silicone cable. Requiring two lengths of black and green, long enough to reach from your ATX PSU, to the point you have placed your relay.

The both wires need to be bare wire on each end.

  • Connect one end of the black wire into a spare COM terminal whilst the other end screws into the exit side of the relay marked NC (Normally Closed).
  • The green wire can now be screwed into the PS_ON terminal on the ATX breakout board. While the green wire screws into the pin marked COM on the relay board.

Now at this point in time, the relay now gets power from the ATX PSU. However it still has no switch method. Except now when activated the PS_ON will short with the GND, turning on the ATX PSU.

SKR V1.3 to Relay

STEP 1

This time around we only need one length of 26 AWG silicone cable in green. It must be long enough to reach from your SKR V1.3 to the relay board.

The wiring needs to have an 2.54mm JST-XHP on one end and a Dupont connector on the other.

  • With the green wire attach the JST-XHP end to the signal on the Max_X switch, and the Dupont end to IN1 on the relay board.

Now at this point the relay now gets power from the ATX PSU. It now has a switch method, that will now activate the ATX PSU by shortening PS_ON will GND.

If you was just after a complete kill switch and not a method to be able to control the power supply, then please skip STEP 2 and move on into Configuring Marlin

STEP 2

But wait there is one more cable to go, if you require the ability to control your PSU and not just have a kill switch, this last wire is important.

Final cable needs to be a red 26 AWG silicone cable, that again will reach the from the SKR V1.3 to the relay board.

The wiring needs to have an JST-XHP connector on one end and a bare wire on the other.

  • With the red wire attach the JST-XHP end to the voltage on the Max_X switch, and the bare end to go into the +5VSB on the ATX PSU.

Now at this point the relay now gets power from the ATX PSU. It has a switch method, that will now activate the ATX PSU by shortening PS_ON will GND. Plus when the ATX PSU is turned off the printer will remain in standby mode (+5VSB).

Whilst in standby we can still configure the SKR V1.3 as if via USB power setup. Power to everywhere else including 12 Volts, 5 Volts and 3.3 Volts from the ATX will be shut off apart from the 5 Volts from the +5VSB.

Complete Wiring Schematic

Configuring Marlin 2 for PS_ON with SKR V1.3

Nearly done, a few quick changes in Marlin and we are finished.

Configuration.h

#define POWER_SUPPLY 2 //Yes the xbox one
//#define PS_DEFAULT_OFF // Personal choice if you want it off at startup

pins_BIGTREE_SKR_V1.3.h

Double check within the pins_BIGTREE_SKR_V1.3.h file that the below snippet of code, is included and activated. Remember to change the pin number if required.

#if POWER_SUPPLY > 0
#define SERVO3_PIN -1
#undef PS_ON_PIN
#define PS_ON_PIN P1_28
#endif

Compile the firmware and upload, effects should be straight away.

Thats it, hopefully the SKR V1.3 ATX PSU guide was useful to you.

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