Reduce Fan Speed Using Resistor

The speed of a permanent magnet dc motor is primarily determined by voltage.

Reduce fan speed using resistor. I m not sure how slow the fan will go though. The resistor will dissipate 0 55 50 25w. As for the resistor wattage here comes the good news. 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.

The problem with using a series resistor is that its voltage drop is proportional to current. High protein breakfasts especially ones that include eggs nnbsp have been linked to weight loss reducing reduce fan speed with resistor belly fat in the process add eggs to salads stir frys and sautés or pair them with 100 whole grain toast and veggies for a hearty breakfast. You could also use a simple 1n4001 diode in series with the positive wire to drop 7 of a volt for each diode you use doing it this way still lets you draw exactly the same amount of current about 500ma and it purely drops voltage and nothing else whereas a resistor in line will have an effect on current also. On the third position 3 resistors takes part and on the last position there is no resistor connected.

So it s easy to see now how any voltage can be obtained with a resistor voltage divider circuit. The more the resistors that takes part the more the voltage drop generated thus the less the speed of the motor. Say if you have the same circuit above with 5v but only want 1v. Let s do one more example.

But notice that you are wasting 15w 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. You can use a selector with more positions for more speed adjustments. If you add a resistor of 50 ohms then you will have an effective load of 400 ohms which will reduce the current by 220 400 0 55 and the voltage across the fan will be 190v.