- #1
Alex Hughes
- 54
- 13
So I have two formulas for calculating voltage drop. The first is: Vdrop = Vin * R1 / ( R1 + R2...). This let's me calculate the voltage drop on the first resistor in a series of 2 resistors. You can also extend this to more resistors in series just by summing all the resistors. However, I do not find this useful in designing circuits because there is nothing to tell me what resistors to use. You sort of have to just keep plugging values in until you get the voltage drop you want. The second is: R2 = Vout * R1 / (Vin - Vout). This formula is more helpful to me because it allows me to calculate what resistor I would need (R2) to put in series with another resistor (R1) in order to achieve a certain voltage drop (Vout) if I have a given voltage from the source (Vin). The problem with this formula is I don't know how to manipulate it to allow me to calculate what resistors I would need to have for circuits where I would need more than 2 resistors in series. For example, if I had a 12v battery, and I wanted to drop the voltage to 8V, then 6V, then 3V, then 0. How would I calculate what resistors I would need to put in series to achieve this without just plugging in random resistors. Does anybody know a formula/method I can use? Thanks.