Xbox PSU and Power_ON "flickering"

Hi all,

I have a Xbox PSU 203W and want to use it with my Printer.
Currently I have it all wired and working fine BUT I also want to be able to control it's power using the M8[0-1] commands.

I did wired the Power_ON cable from the PSU to the RAMPs 1.4 and it effectively works but what happens is that the power is not stable.
The PSU led keeps flashing between green-red and the supply is clearly not constant I can hear the fans and even the steppers falling as if the power
is constantly changing between on and off. I can only describe it as flickering.

If I try to shunt the Power_on cable from the PSU to the 5V standby cable it works fine, solid green led and all working as it should.

It seems that the RAMPS/Firmware isn't keeping the Power_on Pin constantly pulled high, but I'm unsure how to tackle this.
Any ideas?

Thanks!

Edited 1 time(s). Last edit at 05/21/2015 12:42PM by Nandox7.

Have you checked for loose pins and connectors? Have you checked voltage between the blue wire and ground to see if it's being held high, sagging, or dropping out completely?

What are you trying to power using this PSU? I have a heated bed that takes about 11 Amps, a hot-end heater that takes around 3.5 Amps, and I found that trying to power these and drive the motors from a 203W XBox power supply would cause the PSU's LED to briefly flash red, which meant that the control board would reset.

Replacing the XBox PSU with a 30 Amp alternative fixed the problem.

The moral of the story is - an XBox PSU is fine for a printer without a heated bed, but is right on the limit with one.

@cdru, just checked it. It was pulling the pin high with 3,80v.
Found that odd and as it was plugged to my RaspPi over USB I decided to plug to my laptop.
And magic happened I managed to get 4.80v when pulled high and it started working.

Odd thing is I plugged it back over USB to the RaspI and it works fine now.

@David J, I was not even printing. It was just turning it on.


My RaspPi is powered by and external PSU so it shouldn't be a problem but honestly I don'y know what might have been.
I plan to power the RaspPI using the standby 5v from the Xbox PSU so let's see how that goes.

Thanks for the replies.

How do you have your 5VSB (red wire) wired to your ramps board?

Good question.

Actually before was powering the servos rail, so it was connected opposite to the power_on pin into the VCC pin.
Now I have it out.