Electronic – arduino – How to power a 1.5V motor with a 3V source

arduinomotor

I just started getting into electronics so I'm still a major noob. Any help would be much appreciated!

I have an Arduino UNO and have made a few basic circuits with LEDs and a small speaker using examples online. I recently learned a few of the electronic circuit equations like Ohm's law and am ready to start designing my own simple circuits.

I have a 1.5V-3V motor I'd like to try running with my Arduino. The issue is that the Arduino only has 3.3V or 5V power sources. I tried to use Ohm's law to figure out what kind of resistor to use, but I can't figure out what the resistance of my motor is. Am I wrong in thinking that a motor is the same as an LED? I assumed since both were diodes they would function the same way.

I'm attempting to make a simple source-resistor-motor-ground circuit, along the same lines as the simple resistor-LED circuits. I've seen people online say that PWM would work, but I wanted to try without it.

Best Answer

Motors are basically resistors. While others here will crucify me for saying that, this a basic analogy that's useful for beginners to understand. A motor is a long wire wrapped around a core, that interacts with magnets to spin. All wires have resistance and can be measured like a resistor (use the ohmmeter part of your multimeter).

A basic implementation of ohm law can be used. V = IR.

As you have noticed, the motor is intended for 1.5V to 3V. Motor specs are averages, and rely on specific conditions. Your motor provides X RPM and consumes Y current at Z volts. It will be faster/stronger at 3V than it is at 1.5V, while consuming more current, just like a resistor consumes more current at a higher voltage.

You can use PWM to control the motor, reducing the power compared to the percentage of the PWM signal. Or you can use a resistor to lower the current of the motor (two resistors in series combine the total resistance). Or you can realize that since the motor can accept more or less than its "Typical" voltage, you can give it 3.3V without much issue. It will just be a bit faster and consume a bit more energy (10% more).

Alternatively, you can use a silicon diode in series to drop the voltage 0.7V.