Thread: If anyone knows where to find cheap DC-DC AT PSUs, speak now.

Originally posted by Skraggy_uk
I may have an idea that is so fantastically simple that I'm surprised it hasn't been mentioned before.

Will give more details when I know that the PSUs are out there first.

I'm sure it has

Originally posted by frodobaggins
I'm sure it has

OK, seeing as you replied, I'll tell more.

I've been thinking about the DC-DC boards that have started to appear.

And while not so much a problem now, but how the DC-DC PC PSUs available at reasonable prices used to be the AT based ones (seen a few bought in error in the buy and sell forum on here).

Now if you have one of those AT ones, or know where a job lot is going cheap (old hospital, ex server centre that is upgrading, or a Surplus place that has grabbed them), and don't want the expense of a buying an ATX one, or have a Cubid or other mini DC Converter board that you want to regulate, but use with a different CPU/Mobo, how about this.

Us the 12v line of the AT PSU to provide a clean 12v feed to the Epia/Mini PC board.

Or alternatively, use the Mini PC to provide an ATX header to an AT PSU (off the 12v Feed).

All the big peripherals could be run from the AT PSU, smaller ones from the DC board. Most of the 60w going to power the CPU.

You could use a relay to operate the hardware on/off switch on the AT PSU, and a relay in the 12v out line to operate the power good on the DC-DC board that way the whole thing could be switched on from the Headunit remote line or an ignition feed.

What do you think, a good use for AT PSUs, and a reasonable way of regulating power to the DC-DC ATX power boards?

It would probably end up being more trouble than it's worth

Originally posted by frodobaggins
It would probably end up being more trouble than it's worth

How do you mean?
with an DC_DC AT PSU the 12v line output is regulated, but it can't run a modern ATX board.

The ATX power board needs a regulated 12v.

I realise that the two relays was a bit simplistic, although, it is a popular way of firing up dual PSUs (normally just splice the power into the powergood on the second PSU but a relay would be safer) on heavily modded desktop/tower cases where accessories need more juice than a standard PSU can provide.

For someone who has a DC/DC board, and has access to an AT PSU, it might be something to try. Especially with when the AT could take all the load of the periphs (drives/screen/ etc).

UPS circuits/Startup/shutdown controllers could be used to make things more complicated if you really wanted.

I can see your idea, it's not a bad idea however it's not very practical.

Is the point to reuse AT power supplies, or to create a cheap ATX PSU?

If you're trying to reuse an AT power supply, then why not just create a daughtercard to handle +3.3V, 5VSB and PS_ON?

Both the AT PSU and ATX daughtercard would be fed directly from a relay connected to the car mains.

The +3.3V rail can be fed directly from the relay, using an LM2587T-3.3 or MAX788 with 2 caps and 2 inductors.

The 5VSB can either be created the same way as the +3.3V rail but connected directly to the car mains (do this if you want to leave the computer in standby mode for a long time). Otherwise you can take the cheaper route and just use a linear regulator and a capacitor, connected directly to the remote line.

The PS_ON would use a general purpose transistor amplifier, 10K resistor and be used to turn the relay on (this draws it's power from the motherboard which in turn uses the +5VSB).

So you'd need a relay, a MAX788/LM2587T-3.3, 3 caps, 2 inductors, a linear regulator, a general purpose amplifier and a 10K resistor to turn your AT PSU into an ATX one.

If you're not trying to reuse an AT power supply, then remember that the only problem with the 60W 12VDC->ATX PSU is that the +12V rail is fed directly from the car mains and is unregulated. Thus to remedy this problem you only need to post-regulate the +12V output from the PSU, which would require an LM2587T-12, a T6 transformer, a 1N3819, 3 caps, and a resistor.

Your method will require an AT PSU, a 60W 12VDC->ATX PSU, a relay and some way to hack up the 60W PSU to trigger the main relay which would control both PSUs (easiest is to probably just use the same method as I mentioned earlier to create the PS_ON).

So both of the above methods are much cheaper and not all that much more complicated than buying an AT PSU to provide a regulated +12V, and buying the 60W 12VDC->ATX PSU plus components to hack them together. In either case since there are so few components, you don't even need to worry about printing a circuit board, you can just use a plain unprinted circuit board and use some small wires to attach all the components together.

Good try though

By the way do you have check how cheap are the magicpower now?

20 of this unit will be in europe soon...

If you need one.

Originally posted by PTCruiser
By the way do you have check how cheap are the magicpower now?

20 of this unit will be in europe soon...

If you need one.

Yeah, I've seen.
And as usual too late

I had an ATX PSU, and have just bought an inverter so I need to keep the costs down for this version.

I have to convince my GF that it is worth the cost.

Then i have to convinve her it will work.
That is my MK1.

once I have convinced her my MK1 works, I can then build her one, using her car as the prototype for the MK2. Once that is built, it will go into her car, and then I can think about building myself one.

i guess the general idea was a good one, but I don't know enough about electronics to have worked out the fine details.

Still, i'll keep posting the ideas, and you can keep shooting them down.

one of them one day might actually work. (Shock Horror)

That's the spirit Skraggy!

Better to come up with ideas that aren't so great, than not to think at all