# Thread: How to power 5V usb hub from 12v

1. ## How to power 5V usb hub from 12v

I have 2 usb hubs that i need to power from 12v. The hubs need 5v, 2.5A.

Can anyone tell me what i need so that i can power these from a 12v line from the car, i dont want to power them from my M1-ATX psu as it will probably take me close to maximum power.

As it will be powerd from the car, would i need a regulator aswell?

Im not too sure how to go forward from here so any help is appreciated.

2. yup, get a regulator

3. So a regulator would regulate the 12v coming form the car, but how do i convert the 12v to 5v?

4. you can get regulators that have outputs at different voltages, eg 12 > 14 in, 5 out.

5. Thanks, ill look into it

6. good luck getting 2.5 amps though... linear regulators are generally only rated for like 1 amp (because of the way a linear regulator works, it dissipates a the voltage difference as a lot of heat)

if you need 2.5 amps output you'll probably want to go with a switching power supply, which can provide much higher output current without generating nearly as much heat. otherwise, you may have to make some ghetto arrangement of 5v linear regulators in parallel with huge heatsinks.

check out the max787 or max788 (can't remember which one is for 5v) but those are switching regulators designed for 5A output. you just have to add some external components (inductor, capacitors, etc) but if you can solder and read a schematic you should be able to rig something up.

7. I have used 2pcs 7805 regulators with a cooler...
working just perfect...

8. Thanks to everyone who posted their ideas.

I just used the epia power calculator and im actually using less power than i thought. At idle im using about 3.5A, playing MP3 about 4.5A, and playing dvd at 5A. This leaves me 5A spare.

For the two hubs i would pull another 5A, which takes me to the limit. But thats assuming that all ports are using 500mA, when some would be less (i think 100 - 125 mA for some devices). Also one hub would have all ports used up, but the other is just to give spare ports if i ever need to plug anything else in.

Am i right in thinking that the hub would only draw the stated 2.5A with all ports using high power devices?

With this in mind, do you think i would be ok just to suply the hubs from the psu?

9. Originally Posted by spaceman
Thanks to everyone who posted their ideas.

I just used the epia power calculator and im actually using less power than i thought. At idle im using about 3.5A, playing MP3 about 4.5A, and playing dvd at 5A. This leaves me 5A spare.

For the two hubs i would pull another 5A, which takes me to the limit. But thats assuming that all ports are using 500mA, when some would be less (i think 100 - 125 mA for some devices). Also one hub would have all ports used up, but the other is just to give spare ports if i ever need to plug anything else in.

Am i right in thinking that the hub would only draw the stated 2.5A with all ports using high power devices?

With this in mind, do you think i would be ok just to suply the hubs from the psu?
Sure you can. Or, you can use this regulator.

Good for 5 amps, and adjustable. Needs I think one or tow external components, a variable resister and a cap, I think.

Michael

10. Thanks

Im not all that electronically minded, looks a bit confusing with all the different diagrams. Anyway i ordered some samples of it, so ill see how i get on when i receive them.

Do these maintain a constant output, even with a varied input ( 12-14v)

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