If this design works out well, I can rev it again to do that. The caps for the 7905 are already SMD, but maybe they could be a little smaller physically. They have to be tantalum per the spec sheet.

I also really wanted to use the Molex board lock 24-pin connector too, but it is sold out everywhere reputable until mid-year restock.

Be careful about what Pico ATX you buy, the ones I could find specs for most of their wattage was basically 12V passthrough, very little down low where oldskool needs it.

I am still on the lookout for one that is "ample" rather than "might work but it's close" ... but I can skip the AT/ATX bit because I'm looking at AT boards with ATX connectors on for the project I have in mind. I have thought it's maybe just easier to bundle up 4 DC-DC converters with known decent ratings... rather than play "guess what voltage drew the short straw" on the Pico ones.

Yea, don't buy the Chinese knockoff Pico PSU's. The real PicoPSU can output roughly the same amount of amps on both the 12V and 5V rails. They obviously shouldn't be used in late AT systems, but rather for Pentium MMX and prior AT or SBC systems.

wiretap wrote on 2022-02-21, 03:09:

Yea, don't buy the Chinese knockoff Pico PSU's. The real PicoPSU can output roughly the same amount of amps on both the 12V and 5V rails. They obviously shouldn't be used in late AT systems, but rather for Pentium MMX and prior AT or SBC systems.

speaking of, does anyone have a good link for the best pico psu with highest (real) amp rails?

Smaller version.. this post contains rev 0.3. Same BOM is used as in this post: Re: AT pico psu.

Just note the linear voltage regulator needs to be flush clipped and then soldered so the 24-pin ATX connector sits flat.

Perfect! Gonna have to trim those legs good but should be able to do it.

You could make pads that would mount that fet smd for the tab and pins

Beauty!👌

I ordered some PCB's and parts this morning, so I will be able to test it when they arrive.

wiretap wrote on 2022-02-21, 18:12:

I ordered some PCB's and parts this morning, so I will be able to test it when they arrive.

Sweet! Whatcha think total cost will be? May snag some from ya 😀 or make my own.

Can there be a one click link to order them like a mouser? Project.

Sphere478 wrote on 2022-02-21, 18:30:

wiretap wrote on 2022-02-21, 18:12:

I ordered some PCB's and parts this morning, so I will be able to test it when they arrive.

Sweet! Whatcha think total cost will be? May snag some from ya 😀 or make my own.

Can there be a one click link to order them like a mouser? Project.

They are around $13 each to build. There isn't a place to order one fully built. I'm sure PCBway could do it for a high price though. I'm only making one for personal use because I don't have time to make a bunch, which is why I uploaded the design files and BOM for anyone to build their own.

wiretap wrote on 2022-02-21, 18:55:

Sphere478 wrote on 2022-02-21, 18:30:

wiretap wrote on 2022-02-21, 18:12:

I ordered some PCB's and parts this morning, so I will be able to test it when they arrive.

Sweet! Whatcha think total cost will be? May snag some from ya 😀 or make my own.

Can there be a one click link to order them like a mouser? Project.

They are around $13 each to build. There isn't a place to order one fully built. I'm sure PCBway could do it for a high price though. I'm only making one for personal use because I don't have time to make a bunch, which is why I uploaded the design files and BOM for anyone to build their own.

Okay, lemme know how the beta goes. I may decide to make one of my own.

Not a bad project for honing your soldering skills on really, no super sensitive components, and the surface mount fiddly ones are super cheap parts, so get several times more then you need, so if you're messing them up, you can flick them off into trash and try a fresh one.

edit: Though come to think of it, I think getting boards made, the surface mount parts are on the cheap side to get preinstalled and put the through hole stuff on yourself. At least for regular resistor, LED, capacitor, stock logic etc... and though I say cheap, it's still a good few bucks, and may only be worth considering for batches of 10 boards up, not one offs. At least that's the way I hear of hobbyists doing small runs, get all the bulk fiddly bits done at board co, put the through hole and special parts on yourself.

Yea with JLCPCB, their assembly service for SMD stuff is dirt cheap, and they always have coupons. But for this board, the small SMD stuff (well 0805 small) isn't necassary unless you want to populate the lights. Those tantalum SMD caps are huge, and are actually easier to solder than most through hole components.

I wonder if the next evolution of this could maybe be a higher amp version of atx2at.

I love my atx2at but 8a5v is about a few amps short of a usable solution for socket 7. And mounting it directly to the plug is a decent way to mount it which the atx2at leaves kinda open ended.

This is a pretty robust design on the 5V layer. I'd have to calculate how many amps it can pass, but it has the current distributed to 4 pins. On this latest rev, I upped the thermal relief spokes to 0.75mm each. So in reality you have roughly 0.75mm x 4 x 4 worth of copper trace equivalent. To make a more robust design, you could eliminate the thermal relief spokes in the 5v fill zone (which would suck to solder), and order the board with 2oz copper.

Edit: just calculated it for standard 1oz copper fill. Roughly 7-8 amps since the 5V fill zone is on an internal layer. That's about the limit of official PicoPSU's anyway. Moving it to an external layer would give you about 14 amps since it dissipates the heat better. So maybe I'll make a different revision or model for higher current capacity. As far as the 12v, you can't really do any better though, since the AT connector only feeds a single 12V pin. You'd need to do that with no thermal relief and 2oz copper to get the best current capacity.

wiretap wrote on 2022-02-21, 23:35:

This is a pretty robust design on the 5V layer. I'd have to calculate how many amps it can pass, but it has the current distributed to 4 pins. On this latest rev, I upped the thermal relief spokes to 0.75mm each. So in reality you have roughly 0.75mm x 4 x 4 worth of copper trace equivalent. To make a more robust design, you could eliminate the thermal relief spokes in the 5v fill zone (which would suck to solder), and order the board with 2oz copper.

Edit: just calculated it for standard 1oz copper fill. Roughly 7-8 amps since the 5V fill zone is on an internal layer. Moving it to an external layer would give you about 14 amps since it dissipates the heat better. So maybe I'll make a different revision or model for higher current capacity.

Yeah, without spokes it really really does suck to solder haha.

The atx2at is a active overcurrent device. With oled display.
Re: ATX2AT Smart Converter - Live on Kickstarter!

Concerning the +5V capacity I guess one could always just add a few bodge wires from the ATX to the AT connector on one side of the PCB, especially with the last, smaller revision where the +5V pins of both connectors are pretty close to each other anyway.
Something like in the picture.

Doornkaat wrote on 2022-02-22, 05:36:

Concerning the +5V capacity I guess one could always just add a few bodge wires from the ATX to the AT connector on one side of the PCB, especially with the last, smaller revision where the +5V pins of both connectors are pretty close to each other anyway.
Something like in the picture.

I think you underestimate how many amps that setup can pass. 30a woupdn’t surprise me through all those separate connections in parallel.

I was talking about how many amps the at2atx trips at

If this is a consern, a trick we used on the 18650 pcb projects was to leave the mask off the trace and melt a bunch of solder to it during assembly to increase it’s cross section, a wire could even be soldered to the trace. But it was mentioned earlier that there is an entire plane dedicated to the 5v and the 12v so I think it should be fine.

Question,
I see one pin on the atx is listed as nc.
Is that the -5v?

If so, you should be able to connect it to -5v and the regulator -5v it will only combine the two signals for more stable power.

Sphere478 wrote on 2022-02-22, 06:28:

I think you underestimate how many amps that setup can pass. 30a woupdn’t surprise me through all those separate connections in […]
Show full quote

Doornkaat wrote on 2022-02-22, 05:36:

Concerning the +5V capacity I guess one could always just add a few bodge wires from the ATX to the AT connector on one side of the PCB, especially with the last, smaller revision where the +5V pins of both connectors are pretty close to each other anyway.
Something like in the picture.

I think you underestimate how many amps that setup can pass. 30a woupdn’t surprise me through all those separate connections in parallel.

I was talking about how many amps the at2atx trips at

If this is a consern, a trick we used on the 18650 pcb projects was to leave the mask off the trace and melt a bunch of solder to it during assembly to increase it’s cross section, a wire could even be soldered to the trace. But it was mentioned earlier that there is an entire plane dedicated to the 5v and the 12v so I think it should be fine.

The way I read wiretap's post the adaptor would be able to carry 7-8A from the ATX to the AT connector in total. I was surprised but I didn't question it because I know very little about PCB design. Did I get that wrong, is it 7-8A per pin?

I am not talking about the ATX2AT Smart Converter or wiretap's PICO-AT having/getting similar functions.

The solder for trace reinforcement trick is common on power supplies too. I think I also have some S462 boards that use this approach in their VRM circuitry?

Doornkaat wrote on 2022-02-22, 06:57:

The way I read wiretap's post the adaptor would be able to carry 7-8A from the ATX to the AT connector in total. I was surprised […]
Show full quote

Sphere478 wrote on 2022-02-22, 06:28:

I think you underestimate how many amps that setup can pass. 30a woupdn’t surprise me through all those separate connections in […]
Show full quote

Doornkaat wrote on 2022-02-22, 05:36:

Concerning the +5V capacity I guess one could always just add a few bodge wires from the ATX to the AT connector on one side of the PCB, especially with the last, smaller revision where the +5V pins of both connectors are pretty close to each other anyway.
Something like in the picture.

I think you underestimate how many amps that setup can pass. 30a woupdn’t surprise me through all those separate connections in parallel.

I was talking about how many amps the at2atx trips at

If this is a consern, a trick we used on the 18650 pcb projects was to leave the mask off the trace and melt a bunch of solder to it during assembly to increase it’s cross section, a wire could even be soldered to the trace. But it was mentioned earlier that there is an entire plane dedicated to the 5v and the 12v so I think it should be fine.

The way I read wiretap's post the adaptor would be able to carry 7-8A from the ATX to the AT connector in total. I was surprised but I didn't question it because I know very little about PCB design. Did I get that wrong, is it 7-8A per pin?

I am not talking about the ATX2AT Smart Converter or wiretap's PICO-AT having/getting similar functions.

The solder for trace reinforcement trick is common on power supplies too. I think I also have some S462 boards that use this approach in their VRM circuitry?

not sure how that amperage was calculated. Per pin that sounds about right maybe.🤔 the heat isolators I think are unfairly judged for their cross section but their distance is so short that it’s hard to burn them out. Whatever heat they make is synced to the plane quite effectively at higher amps than you may think.

Anyway. I could be wrong. This is just my hands on experience with other circuits. There may be a element at play here I am not anticipating. Welcome more opinions, just seems like more amps wouldn’t be a issue on this adapter.

So back to my earlier idea,

Pico psu= cool
Atx2at= cool
Atx to at micro adapter=cool

But why have three seperate devices?

What about a adapter like this that incorporated a atx2at but for higher amperage AT mobos? That plugged into the mobo like this micro adapter instead of floating free in the case?