5v power from mobo/psu?

[The Torrent]

i got some rgb led's (ws2812b) linked to a bluetooth controller behind my desk.

I want them to turn on when my pc does. Possibly i might add an external on/off button if i could do it from my pc somehow that would be great.

 

they are 5v, pull 3.5amps at max (all white). 

 

rm750x psu

b450 f mobo.

500d se case

 

i also have a commander pro if i could use that somehow.

 

[Bombastinator]

There is a question implied in the headline but not the body of the post.  Are you asking if there is a way to power these LEDs behind your desk directly using your  computer PSU rather than separately and avoiding the Bluetooth data connection/separate power that you use now to coordinate them?

And only because there is a delay between you turning on the computer and the lights turning on?

 

bluetooth functionally is not power it’s data. 
 

a computer PSU does generally have a 5v DC rail, so it’s not theoretically impossible.  It would need a cord from the lights to the computer though.

 

its sorta sounding like what you want to do is transfer the actual 5v DC to your lights with no cord at all.  wirelessly, and rather than transferring the data that tells them to turn on and use power from their own source you want to just power them.

 

There are huge physics problems with this.  Part of it is LEDs are DC not AC

[The Torrent]

12 minutes ago, Bombastinator said:

There is a question implied in the headline but not the body of the post.  Are you asking if there is a way to power these LEDs behind your desk directly using your  computer PSU rather than separately and avoiding the Bluetooth data connection/separate power that you use now to coordinate them?

 

bluetooth functionally is not power it’s data. 
 

a computer PSU does generally have a 5v DC rail, so it’s not theoretically impossible.  It would need a cord from the lights to the computer though.

yes, just power not bluetooth.

does generally have a 5v rail? which one is it? and will 1 rail be enough for 3.5amps?

cord from lights to computer obviously no problem theres like a 5cm gap.

[BruceWayneofLosSanto]

A hacked usb cord would probably do the trick, would come one with the pc too.  I've seen youtube vids on powering 12v cpu fans from hacked usb cord from the 5v rail and it worked fine, not sure about 3.5amps you should check if usb can do that first.

[The Torrent]

1 minute ago, BruceWayneofLosSanto said:

A hacked usb cord would probably do the trick, would come one with the pc too.  I've seen youtube vids on powering 12v cpu fans from hacked usb cord from the 5v rail and it worked fine, not sure about 3.5amps you should check if usb can do that first.

i think usb 2 is only 500mw

usb 3 is about an amp at max iirc

[mariushm]

A molex (old mechanical hdd) connector has 12v and 5v .. the connector's good for 5A on each voltage rail.

SATA is good for up to 3.5A on each voltage rail, but I really wouldn't use it for more than 3A.

 

If you don't want to cut connectors from your power supply, you can buy a molex -> sata adapter cable or molex->2xmolex adapter cable and cut off the unneeded connectors. You'll end up with the female connector that accepts the molex connector from the power supply and the wires with 5v and 12v and you can simply ignore the 12v wire.

 

 

There's also the option of buying a step-down (buck)  regulator, or in other words a dc-dc converter.

You can then take 12v from the power supply (which is plenty) and create 5v.

Cheap 1$ dc-dc regulators can do 5v 2-3A, here's some examples

 

These can do 3A : https://www.ebay.com/itm/1pc-MP1584EN-Mini-DC-DC-12-24V-To-5V-3A-Adjustable-Step-Down-Buck-Module-New-H7/382253668160

You need 3.5A? Just split the leds into 2 strips of <2A each.

 

[Eigenvektor]

5 minutes ago, The Torrent said:

yes, just power not bluetooth.

does generally have a 5v rail? which one is it? and will 1 rail be enough for 3.5amps?

cord from lights to computer obviously no problem theres like a 5cm gap.

Take a look at your power supply or its manual. Here's an example:

Spoiler

This image shows you what kind of rails the PSU has and how much watts/amps is can supply at most on each rail.

[The Torrent]

2 minutes ago, mariushm said:

A molex (old mechanical hdd) connector has 12v and 5v .. the connector's good for 5A on each voltage rail.

SATA is good for up to 3.5A on each voltage rail, but I really wouldn't use it for more than 3A.

 

If you don't want to cut connectors from your power supply, you can buy a molex -> sata adapter cable or molex->2xmolex adapter cable and cut off the unneeded connectors. You'll end up with the female connector that accepts the molex connector from the power supply and the wires with 5v and 12v and you can simply ignore the 12v wire.

 

perfect, my psu has some molex cables.

just 1 more question.

Someone told me once messing with psu cables voids psu warranty.

Can anyone confirm?

[Eigenvektor]

Just now, The Torrent said:

perfect, my psu has some molex cables.

just 1 more question.

Someone told me once messing with psu cables voids psu warranty.

Can anyone confirm?

I'd say that depends on the type of messing around you do and if it leaves any visible damage on the PSU and/or the cables that are firmly attached to it

[The Torrent]

1 minute ago, Eigenvektor said:

I'd say that depends on the type of messing around you do and if it leaves any visible damage on the PSU and/or the cables that are firmly attached to it

its a modular psu so thats ok.

so in case theres ever a problem and they want wires back i might just buy an adapter and cut that up. thanks.

[Bombastinator]

16 minutes ago, The Torrent said:

yes, just power not bluetooth.

does generally have a 5v rail? which one is it? and will 1 rail be enough for 3.5amps?

cord from lights to computer obviously no problem theres like a 5cm gap.

3.5amps is one heckuva lot of LEDs.  Is 3.5amps the draw of the ac/dc converter you are using to power them now?  If so the draw without the converter might be lower.

[The Torrent]

5 minutes ago, Bombastinator said:

3.5amps is one heckuva lot of LEDs.  Is 3.5amps the draw of the ac/dc converter you are using to power them now?  If so the draw without the converter might be lower.

thats the draw that my lab bench power supply is telling me they are pulling.

 

they are ws2812b led's, 74led/s a meter, 1.4 meters + 6 i left on the side, so 110 led's.

(3.5x5)/110 is 0.15909090909watts per led, which is actually a lot lower than their advertised 0.25w per led. thats at all white though. At rgb they are about 2-2.5amps.

[Bombastinator]

1 minute ago, The Torrent said:

thats the draw that my lab bench power supply is telling me they are pulling.

 

they are ws2812b led's, 74led/s a meter, 1.4 meters + 6 i left on the side, so 110 led's.

(3.5x5)/110 is 0.15909090909watts per led. thats at all white though. At rgb they are about 2-2.5amps.

One heckuva lotta LEDs.  Oh well.  That shoots down SATA.  It’s got to be molex.

I was looking at the RM 750 PSU pin outs via google images.  There appear to be several versions of the model name.  Apparently not all RM 750 PSUs are created equal.

[The Torrent]

19 minutes ago, Bombastinator said:

One heckuva lotta LEDs.  Oh well.  That shoots down SATA.  It’s got to be molex.

I was looking at the RM 750 PSU pin outs via google images.  There appear to be several versions of the model name.  Apparently not all RM 750 PSUs are created equal.

i got the rm750x. x variant.

 

Ill have a look then online just in case. i got a fluke multimeter so i can test anyway to make sure. Thanks for your help, all the best.