# Is it possible to limit current with constant voltage?

#### LEGEND383

Oct 9, 2014
3
For my raspberry pi project I would like to have just the one power lead coming in, then splitting off to the pi itself and a usb hub. I was wondering if it is possible to limit the current that would be sent to the pi to something like 1.5A at 5V (power supply would be something like 5A at 5V) to protect it from over-current, yet also limit the current drawn by the hub to the remaining amperage (eg. 3.5A) so as to make sure there is always enough power for the pi. Is this even possible? If it is, how?

#### Colin Mitchell

Aug 31, 2014
1,416
How much does the pi take?

#### LEGEND383

Oct 9, 2014
3
It's recommended to supply it with around 1.5A at 5V

#### Colin Mitchell

Aug 31, 2014
1,416
That is not the current taken by pi.
It is recommended that my car be stored in a garage 15 metres x 30 metres.
See what I mean? ????

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,509
The rpi will only draw the current it needs. You don't need to limit it. You could use a 1000A power supply. As long as the power supply can supply at least as much as is required, you're OK.

#### LEGEND383

Oct 9, 2014
3
@Colin Mitchell No, I don't see your point. If you need a garage that big to park a car, learn to drive and/or get your eyes tested.

@(*steve*) Thanks for the help

#### BobK

Jan 5, 2010
7,682
Since no one answered the question in the title of the thread...

The answer is no. You can limit either the voltage or the current but not both.

For example, if you have a 5V supply and a device that needs 2A at 5V, there is no way to limit the current to 1A other than lowering the voltage.

Bob

#### Gryd3

Jun 25, 2014
4,098
You could always monitor the current @ 5V and turn off the power supply if the device exceeds the current rating you have set.
The Pi will require more current when starting up, or when it is tasked with some CPU intensive tasks. At idle, it draws much less than 1.5A

#### Bluejets

Oct 5, 2014
6,593
That is not the current taken by pi.
It is recommended that my car be stored in a garage 15 metres x 30 metres.
See what I mean? ????

I understood the analogy...good one.

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