ATX Power 1.1 - Power Supply for Arduino & Devices

Released today with the cooperation of electronics the solution I found optimal to solve a lot of powering problems: ATX Power 1.1 Project documentaion and download, images and the product at the following link:

Cheers, Enrico

ATX powers are nice (when they work, that is...) But, don't they require some kind of a load to function properly? Also, I'm not sure a 555 is really necessary? Isn't it enough to just ground the power-on signal to get it started (with a load)?

Nice writeup though!

I've used a pretty old one (200W thing), that doesn't even have the power-on signal as far as I remember, just a switch for the mains. The power_good signal is routed to a LED power-on indicator. As all I had was a 22 ohm resistor that could be mounted inside on the case and take some watts (no idea how many, like 10 maybe, or more if mounted on a heat sink), I used that on the 12V line. To be able to load it a bit more than with the 5V out, or so I figured at the time. Seems to work nicely, the resistor gets pretty hot but not excessively. I haven't used it without the 22 ohm load so I don't know if it works without it. It's "only" 0.55 A wasted on the 12V out which is capable of 8A - now 7.45A left. At least it should give a more stable output voltage with it than without.

Had it for over a year now and basically just used it rather seldom, but for hours at a time when I do use it. However for ordinary "breadboarding" and experimenting I'm actually a bit afraid of it(!) :P I'm sure I'll short something and that one has like 20A on the 5V output... I have another power supply, which can deliver maybe 1.5 amps max, variable voltage, so I'll use that and a 7805 voltage regulator usually.

Gotta say google is pretty amazing.. from the few keywords I managed to cobble up, I found the article I based mine on: From the quick read-through I did just now, the PS-ON signal is active-low, not active-high btw.

Hi, I never told (I think or it is and error) that the power-on signal is active high. In the configuration of a logic switch (that I think is more efficient than a simple gnd connection) the bi-stable NE555 works just with the two conditions. I saw the article in your link and probably we are speaking of different versions. ATX PS I refer to are at least powered with a logid activation. I saw in a lot of other parts that the difference is that as in the ATX Design Guide you can find, with a ground shortcut there is not the same stability.

If you consider the employement of a ps in lot of projects, I think that to buy a new one (400W) at 20$ is not a bad choice.

some atx power supplies require a minimum load on each of the rails also, if you go looking around you will start seeing some with large resistors and heatsinks to burn off the x amount of power needed

The problem that the ATX PS require a minimum load is captious. As a matter of fact, when you power on your PC it's obvious that at leat the motherboard and coolers starts, powered by the PS. In the same way, as you power on your ATX connectd i.e. to a cnc controller, the controller the same is powered and the load problem doesn't exist.

its not much of a load, and yes it does exist, ATX power supplies never shut fully off unless you kill the AC entering them, that is how things like suspend to ram and power management work (heck that is how the power button works, which is connected to the mainboard and checked against bios to see what action to take)

we never had those items with AT/XT systems

not ALL atx power supplies require this, but SOME will (especially your cheap and old ones)

here look at the atx spec’s (page27 is what I will be referring to, section 3.4.3)

No damage or hazardous condition should occur with all the DC output connectors disconnected from the load. The power supply may latch into the shutdown state

Doesn’t say it HAS to, just says it can not cause damage or a hazard, but you MAY if you wanna (and a lot do)

Yes, this is a problem that I don't considered, because the PS is connected to the controller board, in my case. But you told before that some type of ATX PS need a minimum of load, not mine ! ;)

I'm happy to be sure that if - in some cases, as I was supposing - ATX don't need load. I can leave it in power-on state also with all load disconnected.

Cheers :)

most that I have ran across that need a minimum load are those aweful BS gray box supplies you buy from bob's computer shack for 15 bucks

usually rated for 400W (50 on the 12v rail 200 on the 3.3 and the rest just made up) so ashamed of it you usually cant even find a brand name

most of the brand name ones, and ones pulled out of decent computers as of recently have been really good about being designed without the shutoff

until I got one out of a HP server a number of months ago, so its a gamble (unless you have a box of them to try)

I understand. Here (I live in Italy), to have a good quality product I spent 20 ? (about 25$) and bought a new ATX12V full compliant ATX PS 400W of the last generation. :)

mmh, I think "picoPSU" should be the way we build an arduino compatible adapter....

Have a look at "picoPSU".

Specs and pricing looking nice for this task i think...

Greetings ChrisS

Nice !!! :)

In the cases I'm working on, I needed a power box external because it is used to a milling machine controller (with arduino too). Where I can find more ? Link ?

Edited the above posting already to link the manufacturer shop.

Greetings ChrisS

Hi Chris. Thank you. It's as I was suspecting ... This nice think I already know, but it works with a power laptop pc (portable). The ATX Power project is for work with higher currents (2 - 5 A, 250-400W).

Please, take a look to the project and the others released or I'm releasing to the following link:

If you know that distributor, can you help me? I'm searching for resellers / distributors worldwide.

Thanks in advance. Enrico

mmh, I think "picoPSU" should be the way we build an arduino compatible adapter....

The picoPSU is a pretty awesome option; I have one running a system consisting of a Intel ATOM Mini-ITX with 2 gig of RAM, dual-250 gb SATA drives, the SATA RAID controller (PCI), and a "hacked" 802.11g wifi router; the system runs completely off the PSU, no problems.

Well worth the money.

yea for a computer they are but you plug a brick into them then it converts voltages

well you can plug a brick in to a arduino …

see where I am going :slight_smile:

yea for a computer they are but you plug a brick into them then it converts voltages

well you can plug a brick in to a arduino ...

see where I am going

I was meaning it more as a "power supply option", not really for the Arduino; I understand that you could just plug the brick into the external barrel jack (or VIN) and go thru the on-board regulator - that would make more sense for most projects...

Now, if you were bypassing the regulator, or using/building a standalone system where you needed possibly more current than a regular regulator could give, you could put the mating ATX connector (Molex MiniFit Jr line, IIRC) on the board, and then easily plug in the PicoPSU (or even a regular ATX PSU) to power the entire board. Granted, though, this kind of setup would only be useful in a minority of cases and needs, most likely...


The different idea of ATX Power is to use ATX PS independently from the pc to work powering arduino and other devices that need more current and - possible - differente voltages.