Continuous DC Motors in Detail!

This is the type of motor most people are familiar with in battery-powered toys. A motor body, usually round, drives a mechanical shaft at a certain rate of speed. If you connect something like a wheel or pulley to the motor shaft, the wheel or pulley turns.

Continuous DC motors turn when the electricity in coils makes a magnetic field which is opposed by permanent magnets in inside the case. Contacts (between the yellow and green wires in the diagram below) change the direction of the current every half cycle, ensuring the coils continue to oppose the magnets and maintains motion.

Motion inside a DC motor (credit: Wikipedia user Wapcaplet, CC-SA-3.0)

Continuous DC motors are cheap and plentiful - they're available in nearly any size and speed. Often they are customized to the exact needs of a product!

robotics___cnc_dc.png
Examples of continuous DC Motors (ungeared) in various sizes (credit: Adafruit)

Motors have a body (the main bulk of the motor) and a shaft  (the part in the center that turns). Some motors have a gear attached to power something.

The motors above most likely need a motor mount - a bracket of some sort to hold it in place. Common mounts are aluminum or plastic (3-D printing is good for mounts).

Geared Motors

Continuous motors are very fast - rotating at thousands of RPM. This is often too fast for a project, so to slow it down we use gears. The gears slow down the motor and at the same time increase its strength ("torque")

When the motor comes with several gears as a package, like the one below, it is called a Gearbox DC Motor

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Gearbox Motor - this packaging goes by the nickname TT motor (credit: Adafruit)

Geared motors likely turn slower than the actual motor shaft. But due to the gearing action, the motor is able to provide more torque - a stronger turning force - which is great in effectively moving a load.

The yellow motor above, called a TT Motor, is a common size for hobby projects as it is powerful and affordable. TT Motors also are easy to mount due to the body shape and provided mounting holes.

As you can see on the right it uses a fully plastic gearbox. This makes it inexpensive and light.

You can also get TT motors with metal gearboxes. They look a lot like our yellow all-plastic-gearbox motors but these have all of the motor gears machined from steel, so they won't strip as easily, and they're twice as slow (and twice as powerful) given their lower gearbox ratio. The metal gears also mean they're louder when running.

Picking a Continuous DC Motor

When looking at continuous DC motors (geared and ungeared), you will want to look at the following characteristics:

  1. The body size, shape, and weight. What type of mounting points (screw holes, brackets) does it have?
  2. What type of connection is on the shaft to help connect a wheel, pulley, etc. to the motor?
  3. How fast does the motor shaft spin at full speed? How much torque (rotational force) does the motor have?
  4. Does my application need the speed & torque that a geared DC motor provides?
  5. What voltage does the motor run on and what electrical current does the motor draw when
    1. starting up
    2. running full speed
    3. stalled (if the shaft is grabbed so it cannot rotate)

Buying Guide

Here are some motors in the Adafruit Shop which have been hand-picked for various applications you may be looking for:

Gearbox DC Motors

DC Gearbox Motor - "TT Motor" - 200RPM - 3 to 6VDC

PRODUCT ID: 3777
Perhaps you've been assembling a new robot friend, adding a computer for a brain and other fun personality touches. Now the time has come to let it leave the nest and fly on...
$2.95
IN STOCK

TT Motor Bi-Metal Gearbox - 1:90 Gear Ratio

PRODUCT ID: 3801
These durable (but affordable!) gearbox motors (also known as 'TT' motors) are an easy, low-cost way to get your projects moving. This is a TT DC Bi-Metal Gearbox...
OUT OF STOCK

TT Motor All-Metal Gearbox - 1:90 Gear Ratio

PRODUCT ID: 3802
These durable (but affordable!) gearbox motors (also known as 'TT' motors) are an easy, low-cost way to get your projects moving. This is a TT DC All-Metal Gearbox...
$5.95
IN STOCK

Continuous DC Motor (Ungeared)

CD DVD Spindle Motor

PRODUCT ID: 3882
What's this? A record player for ants?? Not at all! This is a DVD/CD Spindle Motor, that thing that's inside a CD or DVD player, that turns the disc...
$1.95
IN STOCK

DC Toy / Hobby Motor - 130 Size

PRODUCT ID: 711
These are standard '130 size' DC hobby motors. They come with a wider operating range than most toy motors: from 4.5 to 9VDC instead of 1.5-4.5V. This range makes them perfect...
$1.95
IN STOCK

DC Motor in Micro Servo Body

PRODUCT ID: 2941
This tiny DC Motor in Micro Servo Body is an interesting motor - it's the same size and shape as our micro servo but it isn't a servo. It's...
$3.50
IN STOCK

Accessories

The main accessory you should consider is how to hook the part of your project that needs to spin to the shaft of the motor. 

For larger shafts (5 mm to 10 mm), Adafruit sells shaft couplers that fasten using set screws.

TT Motors have a specific shape to their shaft, making it easier to press fit various parts made specifically for a TT motor shaft. Parts including various types of wheels, pulleys, and shaft adapters make for flexible connections.

TT motors also easily support attachment of special disks that, when used with a sensor, can help encode the position of the shaft.

Orange and Clear TT Motor Wheel for TT DC Gearbox Motor

PRODUCT ID: 3766
Usually when one needs an orange wheel it's a garnish for a cocktail, like a tasty Sidecar. And speaking of cars, this wheel is for driving, not...
$1.50
IN STOCK

Thin White Wheel for TT DC Gearbox Motors - 65mm Diameter

PRODUCT ID: 3763
We're keepin' it wheel with this one! Plastic gear-box motors (also known as 'TT' motors) are an easy and low cost way to get your projects moving. But...
OUT OF STOCK

Skinny Wheel for TT DC Gearbox Motors

PRODUCT ID: 3757
Plastic gear-box motors (also known as 'TT' motors) are an easy and low cost way to get your projects moving. But we've noticed that there are not a lot of nice TT motor...
$2.50
IN STOCK

TT Motor Pulley - 36mm Diameter

PRODUCT ID: 3789
Mechanical transmission for the win, this simple plastic pulley can attach to your TT motor to transmit rotation from the motor axle to...somewhere else.This is a very...
$0.75
IN STOCK

DC Gearbox "TT" Motor to LEGO and Compatible Cross Axle

PRODUCT ID: 3810
Who doesn't love LEGO and compatible bricks? Nobody! Except when we accidentally step on them. There are soooo many mechanical things one can make with those ubiquitous...
$3.95
IN STOCK

TT Motor Encoder (Pack of 2)

PRODUCT ID: 3782
Plastic gear-box motors (also known as 'TT' motors) are an easy and low cost way to get your projects moving. They're low cost, durable, and easy to use. The trade-off for...
OUT OF STOCK

Snap-on Hub for TT Motor

PRODUCT ID: 3769
Sprockets, wheels, and gears, oh my! We really like our DC gear motors (a.k.a "TT Motor") but unless you have a 3D printer it can be a challenge to get something...
$1.95
IN STOCK
This guide was first published on Jul 04, 2018. It was last updated on Jul 04, 2018.
This page (About Continuous DC Motors) was last updated on Sep 23, 2020.