What wattage resistor should I use?

The power that the circuit would be delivering to the motor is: Here, a 2 watt resistor would be suitable for the circuit. A lower power rated resistor such as a 0.25W, 0.5W, or 1W resistor would most likely cause the circuit to smoke, since the resistor would receive more power than it could handle.

Which resistor is used in fans?

Blower resistors
Blower resistors are resistors which are used to control the fan speed of automotive blowers.

How big of a resistor do I need?

A rule of thumb is to find a resistor with twice the power rating. Here I would choose a 250 mW resistor since those are the most standard ones. Usually, you can just use the cheapest resistor you can find with the correct power rating.

Will a resistor slow down a fan?

Whatever the truth of this situation, a safer option for slowing down a fan is to place a resistor in series with the fan. So to achieve a voltage drop of 5V, we would need a resistor with value of 42 Ohms, and capable of dissipating 0.6W of power.

How many volts can a 1/4 watt resistor handle?

Resistors have a max voltage rating just like caps and other parts. Small 1/4W and 1/2W resistors are usually rated about 200v.

How do I choose the right resistor?

Resistor selection requires three steps:

1. Determine the resistance and the watts to be dissipated by the resistor.
2. Determine the proper “Watt Size” (physical size) as controlled by watts, volts, permissible temperatures, mounting conditions and circuit conditions.

What size resistor do I need to run a fan at 7V?

Here’s how we would calculate the resistor value required to run a fan at 7V from a 12V power source, dropping the voltage by 5V. So to achieve a voltage drop of 5V, we would need a resistor with value of 42 Ohms, and capable of dissipating 0.6W of power.

What size resistor do I need for a 5V voltage drop?

So to achieve a voltage drop of 5V, we would need a resistor with value of 42 Ohms, and capable of dissipating 0.6W of power. This highlights one potential pitfall of this method – you can’t safely use 1/4W resistors for this, unless you make up the target resistance using several smaller resistors (of equal value) in series…

Can I use a 1W resistor to power a 50Ma fan?

Even-though your fan is consuming only 50mA try using a 1W resistor just to be on the safe side. The best way to go with this is to use a voltage regulator like LM317. This particular regulator can be used to st output voltage anywhere from 1.25V to 37V and they can power load upto 1.5A so running you fan should be a piece of cake.

Do I need a resistor or a diode for a fan?

Resistors really only work for constant current flow. You could get away with a resistor as the fan current should be pretty constant when up to speed but the diodes will work well and give you a more defined output voltage. I need to power a small 20mm mini 5v fan.