weedeewee wrote on 2022-05-11, 21:50:

Jura Tastatura wrote on 2022-05-11, 18:22:

Just an idea, to make similar adapter in the same format but 24pin atx -> 20pin atx that would also give -5v to mbo from modern atx psu. I'd buy that, been searching for a long time but only seen atx-at adapters...

Its not a PCB but easiest way to do what you need is get a fully wired 24 atx to 20 atx cable and solder in a 7905 and two capacitors, someone made a small pcb for the components and it's here on the forum but I'm too sleepy to find the link to it.

also, I think the title of this thread should be changed to AT pico adapter :-p

Yeah, that solution would work pretty well. Where is that link btw..? That diamond shaped pcb.

Sphere478 wrote on 2022-05-11, 22:01:

Yeah, that solution would work pretty well. Where is that link btw..? That diamond shaped pcb.

yeah, I think that was it.

Here it is

Re: New solutions to the ATX -5V problem

weedeewee wrote on 2022-05-11, 21:50:

Its not a PCB but easiest way to do what you need is get a fully wired 24 atx to 20 atx cable and solder in a 7905 and two capacitors, someone made a small pcb for the components and it's here on the forum but I'm too sleepy to find the link to it.

Yeah, but I want all the bling-bling, leds, display, like on that smart ATX-AT adapter. 😁

Note: error cap position is reversed

Here is the gerber with that redundant trace removed^

here you can see it's gone (green) and that the via attaches to the 5v plane anyway. (red)

If someone wants to suggest a IC and footprint for making the power switch work with a momentary, and draw a schematic I can give a try at making it fit.

something like this? https://danyk.cz/zap-vyp_en.html

weedeewee wrote on 2022-05-13, 06:34:

something like this? https://danyk.cz/zap-vyp_en.html

Looks like 6? Components?

2 transistors, few resistors and a capacitor.

That’s gonna be difficult to fit…

If we switch to a smd -5v transistor that could save a small amount of room, 🤔

Lookin good..

(This is the previous version.)

hmmm, interesting.

How much juice does the 12v brick need to have?

CalamityLime wrote on 2022-06-03, 08:30:

hmmm, interesting.

How much juice does the 12v brick need to have?

the power supply that feeds the pico psu?

wattage divided by 12v

so, quite a bit 🤣 180w psu would require a 15a 12v brick.

If anyone needs one (pcbs) lemme know.

At that much juice you may want to look into a 4 pin connector for power like on this brick
https://www.mini-itx.com/~192w-ac-4pin

CalamityLime wrote on 2022-06-03, 14:26:

At that much juice you may want to look into a 4 pin connector for power like on this brick
https://www.mini-itx.com/~192w-ac-4pin

Honestly, a car battery charger and a battery would be a good source.
Or a controller and a solar panel with battery

These pico psus seem to be largely carputer oriented.

there is the M2-ATX, looks like that's made to take car/boat batteries.

I've seen the pico psu pop up in a few things. A good example would be what tech tangents did with some PC that had a special psu.
It is tempting to try it for something but I don't have a good use case myself.

Oh btw, some newer psus are 12v only. You could use another psu…. Kinda defeats the point though 🤣

In any case, lets not forget this adapter works with normal psus also.

Repost from another thread to put it in a more suitable thread

3.3 from the pico at could be handy. You'd want a nice stable connector

Some simple feedback:

Pads:
Make the pads for the ATX connector larger (and the AT connector if there's space). The pads you have are on the smaller side, I think you'll find that solder will ball up on the conductor itself without a good contact to the pad. I've had issues with tiny pads doing this on even leaded solder.

Traces
I do see that you have nice thick traces for the -12 and -5 volt rails but to make room for the pads here are some numbers that might help:
You have the thick traces at around 50mil (1.25mm) which is good for around 1.4amps but most negative rails are about half an amp to an amp.
You're not going to see a whole amp on either the -12 or -5 but to accommodate an amp you want around 32mil which is about 0.8mm.

For PWR_OK
It's a signal line so you don't need much. To accommodate say half an amp (can't find a proper spec but it feels right) you want a trace about 0.35mm

I'm giving trace thickness measurements based on 1oz copper, if you're using 2oz copper than you can half the thickness.

Hope that helps a bit.

I had to find some of information on trace thickness for the USB-2-232-KBD to deal with RGB keyboards. Ultimately it came down to fitting the thickest trace I could fit.

I'm thinking about the 3.3v line and I'm thinking that it should probably be controlled by a mosfet.
The power good goes high to tell your computer that the rails have stabilized and it's safe to use the power.

Especially in my case where I'm thinking of pumping the 3.3 into the cpu, it would be nice to have that get power when the 3.3 is good.

I think the easiest circuit for that kind of switching would be an nchannel mosfet on the high side, probably with 2 resistors and a cap. Been a bit since I messed with mosfets and I feel like I never really understood them so I'd have to have a look into it.

If using a mosfet you probably would use the 5v rail because of forwarding losses through transistors.

Anyway, I believe there were AT mobos that used the power supply's 3.3v for the cpu they had a extra connector. If I recall correctly

I was thinking about your comment about voltage loss.

The on resistance of a p channel mos should be about 0.1 - 0.2 ohm. For argument sake lets say it's 0.2 Ohm.
I measured the resistance across power and ground of my socket 3 486 and measured 7000 Ohm. (hopefully esd didn't kill it)

Using those numbers as reference the voltage drop across the mos should be about 0.0001 volts. On paper as I understand it, the reality is probably a bit higher but even so should be within tolerance.
To help with temps then it should probably have 2 phases.

A resistor from source to gate should keep it off then another nchannel mos to switch it on from the 5v pwr-ok line should switch on the circuit. Looking something like the image attached.

Maybe I’m wrong, but I could have sworn that there was like a half volt give or take drop passing through any transistor or diode. Because of forwarding losses