Limiting Current only.

Kurt_ · Post by **Kurt_** » Wed Jul 11, 2007 6:18 pm

I need a way to limit 1500mA to roughly 500mA. Are there any simple ways to do this without altering voltage? I will look into resistors and upping the voltage, but are there any other precise ways to alter current?

Also, is there any proportionalities with ohm's law?

Like if I want to finish with 2.9V 500mAh, I could do something like this (not actual values):

V1 x I1 / R1 = V2 x I2 / R2

(5V)(1500) / 0 = (2.7V)(500) / R2

vskid · Post by **vskid** » Wed Jul 11, 2007 8:43 pm

Why, is it for a battery charger? Otherwise it should just draw as much current as it needs, making this pointless.

Limewater · Post by **Limewater** » Wed Jul 11, 2007 8:50 pm

I'm sort of confused as well.

Why do you need this?

You can build a current regulator, but it's not quite trivial if you don't know the load impedance of the thing you are hooking up to. You'd need to use a transistor and a few resistors.

Or, if you know your load impedance, you can just do a current divider with a resistor or two.

They may actually sell current regulators as components. I wouldn't be surprised, but I've never needed one so I've never looked.

Have you tried searching "current regulator" or digikey?

But again, what is your specific application?