So, you’ve purchased a DC motor, taken the time to install it, and upon startup, you noticed the output shaft is spinning in the wrong direction for your application. Did you install it wrong? Can you reverse the direction of your new motor, or will you have to replace it yet again?
Are DC Motors Reversible?
Are DC motors reversible? Yes! DC motors are capable of running in both clockwise and counterclockwise directions. This reversal of directions can be easily controlled by simply inverting the polarity of the applied voltage. We’ll discuss that further later on.
Why Change the Direction of a DC Motor?
Reversing the polarity of your DC motor magnetic field can be used to slow down, stop, or change the direction of the motor’s spinning force. But why would someone want to do that?
Your garage door motor produces force in one direction to open the door and then has to reverse the direction to close the door again. A hoist needs to move both up and down. Your dishwasher pumps water into the basin and then out again at the end of the cycle. Some ventilation fans move in both directions to either push air into a building or out of the building.
There may even be situations where you wish to stop your DC motor quickly, but you don’t have an electric or mechanical brake installed. Reversing the polarity of the supply voltage will produce a force in the opposite direction, helping the motor to stop quickly.
You can see that there are many practical situations for reversing the direction of a typical DC motor. But how do these applications make it seem so simple?
How to Reverse Your DC Motor
Your DC motor can be configured to turn in either direction by simply inverting the polarity of the applied voltage. The change in the flow of current switches the direction of the spinning force, causing the motor’s shaft to begin turning in the opposite direction.
You can reverse the direction of your DC motor in two ways. You can change the polarity of the circuit at supply or in the field windings. Or you can change the polarity in the armature winding.
A quick cautionary note: Your motor is likely equipped with carbon brushes with beveled edges. This beveled edge helps the brush to drag over the commutator easily.
Reversing the direction of your motor will cause the carbon brushes to be pushed over the commutator, facing more friction than the other direction. This can cause the carbon brushes to wear faster and, if not maintained properly, could cause damage to the critical commutator segments, which are not interchangeable. Your motor’s datasheet will give you specifications on running your motor in nominal and unique circumstances.
Controlling Your DC Motor
You can control your DC motor in three ways:
Manually reversing the armature leads will reverse the polarity of your motor’s circuit. The motor’s datasheet will tell you the direction of the motor from the factory, and it will supply you with the circuit drawings that will show you which terminals are which (positive “+” or negative “-“).
Using a Switch
Installing a toggle or slider switch into the circuit allows the user to control the polarity of the motor. The flip of a switch will change the direction of the motor’s output shaft.
Using an H-Bridge Circuit
Installing a DPDT switch. A DPDT (double pole, double throw) switch is four switches in one that create an H-bridge circuit. It allows you to control your motor in different ways depending on which switches are open or closed at any given moment. Therefore, they can also be used for speed control and not just starting and stopping.
You will want to allow the motor to slow down and stop before switching directions, as quick changes in polarity at high speeds can cause damage to the motor’s circuit, especially if done regularly.
Can you reverse the direction of a DC motor? Yes, quite simply actually. A reversal of the circuit’s polarity will change the direction of the motor’s force. You’ll find this technique applied in a few different ways across many applications, many of which you’ll find at your own home and even in your kitchen.
Take a look at our DC motor control options to take advantage of the full capabilities of your electric motor.