Resistors

[cj_h4x0r]

Hey ya'll, I have been having troubles with resistors. I have been looking through guides and I still cannot figure out how to do what I want. I have a 9v battery, I want to resist it to where it outputs 7.5v. Can anyone tell me the code to do this? Because apparently I am not as intellectual as I thought I was!

h4x0r

[Skyone]

What are you hooking up on the other end? LED? Lightbulb?

Say PSOne screen and I'll shoot you. A 9V battery will simply not put out the load the PSOne screen asks for. If you're talking about a big (2000mAh+) 9v battery, a resistor will not do. Get a regulator.

[cj_h4x0r]

Its for a mini hub I found at the dump, it still works and I just wanted to mess around with it for something to do!

I think I understand it now. On this site there is an equation:

R=(in power-outpower)/A

So mine would be:
R=(9-7.5)/.5

.5 being 500mA in A

So my R value is 3 ohms. So my color code is:
black orange black gold

I think lol.

[timmeh87]

your math is correct, a 3 ohm resistor would drop 1.5 across it under a load of 500mA.

however in practice no one actually uses resistors as voltage regulators like that, because if the load ever changed, say to 100mA, then the input voltage would also change, in this case to 8.7v

and believe me, it changes.

usually you would use a linear voltage regulator, like a 7805 (to get 5v) or something.

it sounds to me like this router actually has its own 7805 in there, since almost all electronic chips run off of 5 volts or 3.3 volts. what that means is you could put any voltage into it and it would still work.

it would be worth it to try to find out if there is a 7805 inside.

also, if you mean a 9v battery like in a smoke detector, then Im sorry but 500mA is way out of its league, the voltage will drop way below 9v because of its own internal resistance.

[dman762000]

or if you just really wanna mess around with resistors on this thing then do what i did and build a resistor bank till you get the voltage drop you want, its fun