# How I decide How much value register need in circuit

#### yash2315

Joined Apr 30, 2021
4
Hello,
I am New in hardware design then how i decide how much register value need in circuit?
I know this equation P= V*I also V = IR etc but i dont know value of this parameter then how i decide please suggest me.

Thanks & Regards
Yash Shah

#### Yaakov

Joined Jan 27, 2019
3,522
Welcome to AAC!

You mean "resistor", of course.

If you could give the specific example of what you are trying to do it will be a lot easier to help. An abstract explanation is not going to be as useful.

#### yash2315

Joined Apr 30, 2021
4
Hello,
I show one schematic and they give 6v Supply using the battery but in output they put 1M and 220k resister after pass the next step output why then put some resister ?why not directly pass the output on the circuit?

Thanks & Regards
Yash Shah

#### Yaakov

Joined Jan 27, 2019
3,522
Hello,
I show one schematic and they give 6v Supply using the battery but in output they put 1M and 220k resister after pass the next step output why then put some resister ?why not directly pass the output on the circuit?

Thanks & Regards
Yash Shah
The function of a resistor is to resist voltage. There will always be a voltage drop across a resistor. If there is a resistor, someone wanted a lower voltage on the other side of it. Since voltage and current (amperage) are inextricably linked, it is often the case that a resistor is put there to limit current.

Your verbal description is not good enough to know what the resistors were doing in that circuit.

#### trebla

Joined Jun 29, 2019
431
The main function of the resistor is limit the current.

#### trebla

Joined Jun 29, 2019
431
Output voltage depends from input voltage, current limiting resistor resistance and from load resitance.

#### yash2315

Joined Apr 30, 2021
4
Hello,
Ya exactly resister limit current now i give some example
I need 0.5A current And i am supply 5v so how to decide the resister value is like as per R=V/I?

#### trebla

Joined Jun 29, 2019
431
Then you need drop 1V on the resistor : R = 1/0.5 = 2 ohm

#### trebla

Joined Jun 29, 2019
431
And dissipated power on the resistor will be at least P = 1 * 0.5 = 0.5 W

#### yash2315

Joined Apr 30, 2021
4

#### trebla

Joined Jun 29, 2019
431
You wrote in the #3 that supply voltage is 6V. If you need at output 5V then you must drop 1V on the resistor.

#### LesJones

Joined Jan 8, 2017
3,498
Provide a schematic of the circuit that you are trying to describe then we will be able to answer your question.

Les.