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300W Power Supply Question

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Sir Topham Hatt    361

An unusual post but I just want to get my head around something.

 

If I have a 300W power supply that is powering just one hard drive, I guess it wouldn't be running at 300W but much less?

 

Coming out from a power supply is a bunch of yellow cables (12v positive) and a bunch of black ones (0v, negative?).

 

Do the yellow ones carry 12v each?

 

Basically, I'm thinking of powering something else that needs a 12v supply. But it would make sense that if I can have one computer PSU but use three or four of the yellow cables to give me three or four different lines of 12v, it would be a lot easier than three or four different power supplies.

 

Cheers! 

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Jim K    15,726

Sure.  I've used a power supply to power on and test my trucks amplifier (turned out to be a bad ground in the truck vs. an amplifier issue). 

 

If it follows the standard color scheme ... the yellow will be +12v.  If you have two rails the 2nd rail probably will be a yellow wire with a blue stripe.  Blacks are ground. 

 

Check the label on the power supply ... what does it say with regards ..

 

IMG_1793.thumb.JPG.954b8b08e1ca0ab5cd37873c65e1dfa0.JPG

 

This old PSU of mine has two +12v rails @ 20A (though I suspect it really is just one rail from one supply circuit since I get resistance between the yellow and yellow/blue)...meaning I could safely bridge the "two" rails if needed.  But I digress.  Don't do that.  🙂

 

Biggest question ... what is "something else" that you're thinking of powering? 🤨  If "something else" doesn't exceed the output delivery of the rail (including any other devices/hardware using that rail) you should be fine.  

 

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Riva    1,345

300W sounds really low to me. What CPU GPU and other devices do you have?

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Mindovermaster    3,695
5 hours ago, Riva said:

300W sounds really low to me. What CPU GPU and other devices do you have?

I think he's using it for other means. IDK...

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Sir Topham Hatt    361
Posted (edited)
On 7/12/2020 at 1:40 PM, Jim K said:

 

🙂

Biggest question ... what is "something else" that you're thinking of powering? 🤨 

 

 

A model railway.

 

Well, maybe part of it - LED lights mainly.

They require a 12v - 16v output. My 16v one would be okay but that is busy running through a CDU for something else on the layout. 

 

I guess I could split each yellow wire up and have 10 different 12v outputs? In the video I watched, the guy just soldered them all together to have one 12v output and one black 0v.

 

No firm plans but perhaps for the future.

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PGHammer    1,764
On 7/12/2020 at 2:36 AM, Sir Topham Hatt said:

An unusual post but I just want to get my head around something.

 

If I have a 300W power supply that is powering just one hard drive, I guess it wouldn't be running at 300W but much less?

 

Coming out from a power supply is a bunch of yellow cables (12v positive) and a bunch of black ones (0v, negative?).

 

Do the yellow ones carry 12v each?

 

Basically, I'm thinking of powering something else that needs a 12v supply. But it would make sense that if I can have one computer PSU but use three or four of the yellow cables to give me three or four different lines of 12v, it would be a lot easier than three or four different power supplies.

 

Cheers! 

I have a low (and getting lower) opinion of sub-500W power supplies for desktop PCs - due mostly to a 400W PSU in exactly the situation you described heading south - taking the motherboard with it.  Multi-GPU desktops - with or without multiple platter drives - do put serious stress on a power supply - which is all the more reason not to skimp.  However, you don't have to spend a mint - or even half a mint; modular PSUs in the 500W and higher range can be gotten for decent prices (the Corsair CX550M - the PSU I bought - is still available, the price is far from princely, and can drive multiple GPUs and multiple platter drives - at the same time.)

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Jim K    15,726
33 minutes ago, Sir Topham Hatt said:

 

A model railway.

 

Well, maybe part of it - LED lights mainly.

They require a 12v - 16v output. My 16v one would be okay but that is busy running through a CDU for something else on the layout. 

 

I guess I could split each yellow wire up and have 10 different 12v outputs? In the video I watched, the guy just soldered them all together to have one 12v output and one black 0v.

 

No firm plans but perhaps for the future.

Yea, all the yellows are carrying your 12V. I don't really see a problem with what you're trying to do at long as you're not exceeding the Amps.  I think (and could be wrong) the wires coming out of the PSU are 20 gauge...which is ~10A rated (not factoring length of wire...the Amp rating will drop as wire gets longer).  No idea what a "model railway" would require.

 

tl;dr yea, they are carrying 12V but don't exceed overall amps of PSU or the individual wires.

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Mindovermaster    3,695
55 minutes ago, PGHammer said:

I have a low (and getting lower) opinion of sub-500W power supplies for desktop PCs - due mostly to a 400W PSU in exactly the situation you described heading south - taking the motherboard with it.  Multi-GPU desktops - with or without multiple platter drives - do put serious stress on a power supply - which is all the more reason not to skimp.  However, you don't have to spend a mint - or even half a mint; modular PSUs in the 500W and higher range can be gotten for decent prices (the Corsair CX550M - the PSU I bought - is still available, the price is far from princely, and can drive multiple GPUs and multiple platter drives - at the same time.)

People are forgetting what he is using this for... A PC isn't one..

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Sir Topham Hatt    361
34 minutes ago, Jim K said:

I think (and could be wrong) the wires coming out of the PSU are 20 gauge...which is ~10A rated (not factoring length of wire...the Amp rating will drop as wire gets longer).  No idea what a "model railway" would require.

A large model railway with a few locomotives pulling coaches with sound would only pull, at best 4 amps.

The controller I have is rated at 3.5 amps, and that's considered quite a lot.

 

As this PSU will be powering tiny LEDs, we're into milliamp territory, so there's a potential to go as low as 100W or even just 60W for what I'd need.

 

Thanks for the help 😊👍🏻

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