ATX conversion question - Page 1
Forum section: electronics / beginners

author: shobo
author_rank: Regular Contributor
timestamp: December 09, 2017, 02:50:16 pm
content: i'm planning to do an ATX conversion to make myself the most basic of bench power supply.The plan is to get a 24 pin extender to breakout the wires and keep the psu untouched.Since the PSU is a really cheap and i doubt it has multiple rails can the power resistor could be added with an adapter to one of the sata cables with an adapter?The resistor i plan to add is a 10w to the 5v line.

author: madires
author_rank: Super Contributor
timestamp: December 09, 2017, 03:33:44 pm
content: Maybe a better option:

author: cdev
author_rank: Super Contributor
timestamp: December 09, 2017, 04:12:06 pm
content: Those supplies still need a source of voltage to regulate, so teaming up an ATX supply with one of them makes sense.An ATX supply with give you a bunch of fixed voltages and currents and could be teamed up with one of the DC-DC converter modules to give you a single output with controlled current for prototyping.That's a good all around solution for a bench.

author: rstofer
author_rank: Super Contributor
timestamp: December 10, 2017, 12:28:00 am
content: I'm not sure why you are using the resistor...Here is a neat way to set up the ATX supply:https://www.sparkfun.com/products/12867Notice that the gadget has fuses. This is important because the ATX has far more current capability than you want to have in a bench supply. The magic smoke comes out of chips really quick when the power supply doesn't limit the current in any meaningful way.

author: phil from seattle
author_rank: Super Contributor
timestamp: December 10, 2017, 01:09:19 am
content: The resistor is there because most (all?) PC power supplies need a minimum load to start.I agree that current limiting is very important, not just with a beast supply. My dual channel, no-name Chinese bench supply has decent current limiting and I will set it to usually about 2X my max expectation. Saved my @$$ multiple times.

author: rstofer
author_rank: Super Contributor
timestamp: December 10, 2017, 01:30:46 am
content: I have read about the resistor requirement but I don't have one on my converted ATX supply and it seems to work fine. I just installed the kit according to the directions and it all seems to work.Maybe things have changed over the years. I would just install the kit and see what happens.

author: Seich
author_rank: Newbie
timestamp: December 10, 2017, 04:05:46 am
content: Quote from: rstofer on December 10, 2017, 12:28:00 amI got that same kit a while ago before I got a proper power supply and it worked pretty well. If it's an option for you I'd go with it. It's fairly painless to setup and is well constructed. The fuses are a nice touch.It's also pretty easy to build a case around. The schematic is also available, if really want a completely diy solution it might come in handy:https://cdn.sparkfun.com/datasheets/Kits/Benchtop%20Power%20Supply-v13.pdf

author: ChrisLX200
author_rank: Unknown
timestamp: December 10, 2017, 08:43:57 am
content: There are all sorts of breakout boards for ATX PSUs, I used a different one but the functionality is the same. Also 3D printed a nice case for it.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: December 10, 2017, 08:54:06 am
content: Cheaper and with polyfuseshttps://m.seeedstudio.com/productDetail/1222

author: rstofer
author_rank: Super Contributor
timestamp: December 10, 2017, 04:39:13 pm
content: Quote from: netdudeuk on December 10, 2017, 08:54:06 amPlus it has the load resistor, if required.Nice!

author: shobo
author_rank: Regular Contributor
timestamp: December 10, 2017, 09:14:50 pm
content: Quote from: rstofer on December 10, 2017, 12:28:00 amThe shipping will kill me.for the moment an ATX extender and a minimum of 4 banana plugs would be something around 7 dollars + a power resistor for 3 and change.

author: robotic
author_rank: Contributor
timestamp: December 10, 2017, 10:26:20 pm
content: Wow didn't know there were so many options. I was going to do the same type of thing (but cut the wires as I have so many power supplies [salvaged from old PCs]). After buying a used power supply, it's been night and day though. I love being able to see the amperage draw and adjusting the voltage and such. I would get the DPS powersupply for $25-$50USD (depending on model).However the ATX conversion is great for simple things like powering my 12v lipo chargers so I don't have to constantly disconnect and reconnect things.

author: SteveSi
author_rank: Contributor
timestamp: October 14, 2019, 03:25:06 pm
content: I am also planning an ATX PSU + DPS3005 + USB PSU.So this gives me all the ATX rails + a variable, current limited rail.However, I really want the DPS3005 to provide 15V max.I thus plan to use -12V and +12V from the ATX PSU to connect to the DPS3005 - but will this give me a problem with the earth - for instance, if I connect the ground of my scope to the 'gnd' output on the DPS3005 then will I get magic smoke?If so, would it be better to get the buck-boost DPH5005 module instead and feed it 12V to get a 0-50V output?

author: janoc
author_rank: Super Contributor
timestamp: October 14, 2019, 04:45:27 pm
content: Quote from: phil from seattle on December 10, 2017, 01:09:19 amMost newer supplies have the resistor built-in, so there is no need for an external resistor. It isn't only for starting the supply up but also to ensure a minimal load current in order to maintain the supply in regulation.The resistor is included in the kit because people often recycle old junk from discarded computers which may not have these.

author: madires
author_rank: Super Contributor
timestamp: October 14, 2019, 05:37:30 pm
content: Quote from: SteveSi on October 14, 2019, 03:25:06 pmThe -12V rail of most ATX PSUs delivers just 0.5A, way too low. The next issue is that the PSU's ground is connected to earth/PE and therefore you won't get an isolated output. And since the -12V rail is going to be ground for the DPS3005 a scope with ground connected to earth/PE would create a short circuit on the -12V rail. Either get a decent PSU or buy the DPH5005 (not isolated due to the ATX PSU).