ATX PSU

[Marius_]

Hi Everybody,
I am proud owner of raspberry Pi. I have one project in my mind that i want to realize, but I cannot do it without your help.
What I want is to build NAS server that will be powered over ATX power supply. As I saw on similar projects on internet, raspberry can be powered via +5VSB ( purple wire) without powering up ATX. Now to power up ATX and hard drives connected to it, you need to connect green wire with COM on PSU. What i want is that my raspberry do it via GPIO pins (or any other alternative as long as it is wirelessly). When it's about GPIO pins I am pretty much noob. I want this because i don't need my hard drives running 24/7, but only when I need them. Is it possible to do that via GPIO pins and is it there...somesort of module that would connect those two wire. Anybody have any idea? Any help would be apritiated. Thank you!

[pluggy]

If you don't know what you're doing I'd stay well away from using an ATX power supply via the GPIO headers. Its very, very easy to destroy the Pi, when you're using the proverbial sledgehammer to crack a nut.

[mrpi64]

I have to agree with pluggy here. Plus, I don't even know if the Pi can cope with the current that an ATX psu shoves out. I would stick to the standard micro-usb supply for now.

[pksato]

Hi, a long time ago, I did this circuit.

This use a NPN transistor (2SC1815, or other, pins can be different), 10k and 1k resistor, all salvaged from fault ATX PSU.
Software is very simple, rise pin to power on and lower to power off, like a led.
More details about circuit, Its is simple, not need a schematics.
Transistor Emitter is connected to ground (black).
Collector to PON (green)
Base pin is floating.
10k Resistor is is connected from GND to transistor Base.
1k Resistor connected from gpio to base (junction to 10k).
This circuit was mounted on ATX main board connector.

But, if have a compatible usb to [PS]ATA bridge, set to put HDD on stand-by mode, after certain time.
Use command like, hdparm -S 200 /dev/sda

[gordon77]

I have to agree with pluggy here. Plus, I don't even know if the Pi can cope with the current that an ATX psu shoves out. I would stick to the standard micro-usb supply for now.

PSUs don't 'shove current out', things 'draw' current dependent on the load. The RPi will only draw what it needs.

The risk here is that a fault / misconnection here could draw a lot of current, which a PSU like this is capable of, damaging the RPi etc.

[davidcoton]

Yes, it's do-able, but listen to the warnings about fried Pi.

I can't see all the details in pksato's post, a circuit diagram would help. It may be usable if your eyesight is better than mine.

There are some questions you need to research to do a proper design:
1) What current is available on the 5V Standby line? Is it enough for your Pi and any peripherals powered from it?
2) What voltage appears on the switch wire when it is open circuit?
3) What current flows from the switch wire when it is grounded?

If you don't understand the questions, or can't find the answers, don't try the circuit.
Question 1 determines whether the idea will work to power the Pi.
Questions 2 and 3 are required to select a suitable transistor and resistors for the circuit. The values are probably not critical within fairly wide limits, but without the information no-one can tell.
I don't actually know the answers, but even if I did, finding them yourself is part of your learning process!

[rpdom]

1) What current is available on the 5V Standby line? Is it enough for your Pi and any peripherals powered from it?

Usually you can glean this information from the label on the PSU.

[Marius_]

Ok, Thank you all for the comments.
I'm giving up on raspberry controlling PSU and Gpio. I think it is too much for a beginner like i am. It's better to leave it as it is and find other alternatives... so i will rephrase my question: There is Green wire (a.k.a PSU ON) on the atx psu. To start the psu, green wire must be connected to the COM (black one). Now, is there some sort of switch (on-off switch) that will be able to make a connection between two of those lines wirelessly? Of course, i can put common on-off switch to power the PSU On, but i want to make it with less wires. Is there some,let's call it, wireless switch that can make circuit between green and black on my demand.
Thank you all once more....

[mung]

I use an ATX psu with one of my projects, but don't really want to offer technical help and risk blame and ire if you blow up your pi.

One thing I have found is that its rather inefficient running ATX PSU if you are only using rpi and low power peripherals, it would be better to buy a simple usb psu.

If you want to run things with molex 4pin and need a lot of power then its useful, the red is 5v yellow 12v, you could run via gpio back powering, but better is wire up a micro usb to molex and plug it into the atx connectors.

I got some really cheap micro usb cables from ebay that do not work as the wire is wrong rating for the current required, but if you cut the cable down to 20cm the voltage drop is less so works fine, then hacked together a connector board.

I maybe post a photo if I have time tonight, but do not recommend anyone uses it without knowing what they are doing.

[pluggy]

One thing I have found is that its rather inefficient running ATX PSU if you are only using rpi and low power peripherals, it would be better to buy a simple usb psu.

+1

Most of the ATX power supplies I've used consume more power in the off state than the Pi uses in total. A handful of watts isn't a lot in PC land, but when a Pi only uses a couple to start with.....

[davidcoton]

... Now, is there some sort of switch (on-off switch) that will be able to make a connection between two of those lines wirelessly? Of course, i can put common on-off switch to power the PSU On, but i want to make it with less wires. Is there some,let's call it, wireless switch that can make circuit between green and black on my demand.
Thank you all once more....

I'm sure there is. But this is a Raspberry Pi forum so it's off-topic. Try google.

[mung]

I don't know why I bother as its probably no use to anyone but I took a photo of one of the hacked up atx psu and usb plugs I have messed with.

I cut up a scrap piece of pcb, hacksaw slots at the width of usb plug and solder wires onto copper that I shave down to width of the usb power contacts, probably takes 5 minutes longer than a simple soldering of micro usb cable onto the molex female socket, but allows changing usb leads if you think that maybe necessary.

Some boards I have put a regulator inline as I have changed the voltage outputs on the atx psu to higher voltage.

rpi model A+ with atx psu

psu6.jpg (63.57 KiB) Viewed 2533 times

usb socker to molex 4 pin power adapter pcb.

psupp.jpg (36.92 KiB) Viewed 2533 times