# How-To: Motors

9 Steps
Servos and Steppers and Gears! Oh my!

Some of our favorite hobbyist electronics utilize motors to mobilize, making them fun and awesome! Including a motor in your project could be challenging, especially if you have never worked with them before.

The following Instructable will explain how motors work, and break down some of the most commonly used kinds of motors.
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## Step 1: The Fundamentals

Before we can really begin addressing how a motor works, lets focus on what a motor does. A motor uses electromagnetism to create motion, converting electrical energy into mechanical energy.

Magnetic fields produce physical force that can move things. Every magnet has a magnetic field with a north pole and a south pole. If you try to push the north poles of two magnets together, they will repel each other. The same thing happens if you try to push two south poles together. If two poles are the same, they will repel each other. If, however, you play with two magnets and bring the north pole of one close to the south pole of another, they will attract each other and stick strongly together, opposite magnetic poles attract each-other.

An electric motor uses the attraction and repelling properties of magnets to create motion. There are two magnets in a standard electric motor: a permanent magnet, and a temporary magnet. The temporary magnet is a special kind of magnet, called an electromagnet. An electromagnet is created by passing an electric current through a wire. The permanent magnet has a magnetic field (a north pole and a south pole) all the time, but the electromagnet only has a magnetic field when there is a current flowing through the wire. The strength of the wire's electromagnetic magnetic field can be intensified by increasing the current through the wire, or by forming the wire into multiple loops.

In an electric motor, the electromagnet is placed on an axle so it can spin freely inside the magnetic field of a permanent magnet. When an electric current is passed through the wire, the resulting temporary electromagnetic field interacts with the static permanent magnet, and attractive and repelling forces are created. This excitation of the wire, or electromagnet, propel it to spin on its axle, and an electric motor is born.

Motors are classified by having the following properties:
• There's a permanent magnet (or magnets) around the edge of the motor case that remains static, so it's called the stator of a motor.
• Inside the stator, there is a wire coil, mounted on an axle that spinsaround at high speed -  this is called the rotor.
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MakeItWithJason says: Apr 22, 2013. 3:20 PM
Awesome illustration for a stepper motor!
MakeItWithJason says: Apr 22, 2013. 3:16 PM
This is a great 'able, Audrey. Thanks!
lemaxnut says: Apr 4, 2013. 3:15 PM
Thank you for your very clear explanation of the various motor types and the videos. I have saved it in my grandsons' "favourites" for the time when they will study this subject. I have already made them many toys using all these motor types - I favour PICAXE as I think BASIC is easier to learn for kids.
ssgsteiner says: Feb 10, 2013. 7:37 AM
very nice, great info and put together well.
jolizo says: Aug 4, 2012. 8:04 AM
Hello.
I would be very happy if someone could help me where I can find servo motor.
I mean, I usually enjoy myself dismounting printers and scanners. And I have never seen a motor like that.

att,

Jolizo
Owlflight in reply to jolizoNov 1, 2012. 8:40 PM
Hobbyking is a good source.
Alderin says: Oct 17, 2012. 8:26 AM
While this is a good rig to experiment with and learn about stepper motors, be careful about the load you put on your Arduino. Steppers and DC Motors can send spikes of current back to the controlling circuitry when switching from on to off due to inductance, as well as possibly drawing more current than your Arduino is designed to supply. For more permanent projects you should get or build a motor control board to isolate the more delicate logic circuits.
dlemke says: Oct 15, 2012. 4:41 AM
A stepper motor seems to be a regular motor, except it's segments are separated, unlike a regular motor where the segments are wired in a series to make the motor run at a constant speed and no controller is needed other than the volts/amps. Now this may be very simplified, but would this be accurate?
WelderGirl says: Sep 15, 2012. 3:57 PM
DavAnt- thanks for that interjection, I was specifically looking to see if the TD62003AP was an acceptable Darlington substitute for the ULN2003. Appreciated!
cesar harada says: Aug 3, 2012. 6:49 PM
coolnits says: Mar 6, 2012. 8:51 AM
I new to complex circuits and arduino. Wat is arduino?.
And do u program arduino with a computer?
if yes - Which language ?

----- curious beginner
jensenr30 in reply to coolnitsMay 2, 2012. 8:48 PM
Coolnits,
Arduino is a microcontroller (like a mini, programmable computer)
You program it using the Arduino IDE (the arduino program-writing software)
You can go to Arduinio.cc for a LOT of good information about the Arduino.
It is programmed in C / C++

-Ryan
burnerjack01 in reply to coolnitsMar 8, 2012. 10:49 AM
Coolnits, Arduino is a very powerful microcontroller which is based on an opensource platform. The website www.hackaday.com can fill you in. Seems to be ONE of the up and coming nextgen controllers. Free software downloads, free manuals and tutorials too! I have it on my wish list but have yet to actually try one or do any work with one, so I can't tell you much more other than it is based on Object Oriented Code. What's that? Dunno. Yet. I do get the Idea that it is quite popular with techies who dive deep. Good luck.
Nirgal38 says: Feb 19, 2012. 2:44 PM
I got the link to this the day after I'd finally figured out how to get a stepper working with my Arduino.

Timing is everything. :)
Arkyro in reply to Nirgal38Feb 21, 2012. 4:55 AM
You should use a ULN2003 IC to drive stepper motors using the arduino! If i am not wrong it is a darlington array..
DavAnt in reply to ArkyroFeb 26, 2012. 6:51 AM
Yes, I got a stepper out of an old UMAX scanner, and it is controlled through a Toshiba TD62003AP, which is a Darlington array. There are also some smd capacitors to smooth it out I guess
airborne82 says: Feb 22, 2012. 4:26 PM
If you don't want to pay for a Arduino board and you know a little about electronics, you can build a stepper motor controller from a 555 timer IC, a 4017 decade counter IC and a ULN 2003 Darlington transistor array. To adjust the speed simply put a potentiometer ( the higher the resistance, the slower it goes) between pins 7 and 8 of the 555 timer IC. The direction can be changed using a DPDT switch from the output of the ULN2003. This works simplest when running 3 phase stepper motors which are commonly used in aviation. There isn't much information on the net about 3 phase stepper motors and how to run them, but I combined knowledge about the 3 ICs and many schematics.
airborne82 in reply to airborne82Feb 24, 2012. 5:24 PM
I have to correct myself. To adjust the speed, put a potentiometer between pins 2 and 7 of the 555 timer IC.
raphsonnewton says: Feb 21, 2012. 1:43 PM
Where can you get the small axle?
kristof.van.opstal says: Feb 19, 2012. 8:29 AM
This is a great starters tutorial for motors! It would be a perfect entry for the teachers-contest!
Jeff Yates in reply to kristof.van.opstalFeb 19, 2012. 10:22 AM
I Agree
stephenfitton in reply to Jeff YatesFeb 21, 2012. 12:21 PM
Are you the Jeff Yates from (Paravet-Computers are here Co)
The inventor of Mr Salty water chlorinator and the Originater of the First Usuable Chineses Computer Keyboard. In which case please take credit for realising my basic theory with Barry to take the stepper motor to its 1,000 degree. If I remember right that took 6 months and \$30,000 to realise, congradulations, Student 6 of 20 pass
stephenfitton says: Feb 21, 2012. 12:11 PM
nice presentation,because you have done so well and like experimenting.
History back in the eighties they wanted stepper motors to go beyond 1.5-3 degrees I offered a solution . by oscillating the fields with different wave lengths and forms,1,000 th of one degree was achievable using the same motors..Keep up the good work.
skrubol says: Feb 20, 2012. 9:39 AM
The brushes are just part of the commutator. They're the switch that keeps the coil at the right polarity to keep spinning. They don't propel anything.

Also I agree with Clemtasm. A constant voltage across an 'ideal' motor will give constant speed with varying load. In real motors the speed drops with higher load due mostly to the resistance of the windings.
Arkyro in reply to skrubolFeb 21, 2012. 4:50 AM
When the load on the motor increases the current consumed by the armature will also increase hence the flux will increase. Speed in inversely proportional to flux. So the speed of the motor has to decrease with increase in load over a constant load. Even in case of an ideal DC motor. Please let me know if I am wrong.
skrubol in reply to ArkyroFeb 21, 2012. 6:41 AM
It's been a long time since I've dealt with theoretical emag, so I'm not sure. In an ideal motor model with zero ohm windings (I think even in an ideal motor, sometimes you will account for winding resistance, depends who considers it ideal..) speed is strictly proportional to voltage and torque is strictly proportional to current.
In a simple motor model (where you do take winding resistance into account, but do not take reactivity or friction into account,) it's pretty easy to deal with the winding resistance. Speed will just be (Vin - Tout/Ka*r)*Kv. Or if you know V and I, just (Vin - I*r)*Kv.
pattyshaw says: Feb 17, 2012. 11:48 PM
This was great but how do i wire a 6 lead stepper motor to an arduino?
Arkyro in reply to pattyshawFeb 21, 2012. 5:01 AM
You need a Stepper motor driver circuit...
elabz in reply to pattyshawFeb 19, 2012. 10:28 AM
It's a unipolar stepper, Arduino has a special tutorial for it here:
http://www.arduino.cc/en/Tutorial/StepperUnipolar All the chips needed for driving it along with the software to step through the windings is mentioned on that page
Be sure to use a motor driver... the Arduino is designed around an Atmel processor which can support a maximum of 20mA from a port, not to exceed 50mA for the entire chip. A typical stepper motor can be 2A which is 2000mA or 400% of what the chip is designed for.

4-wire Steppers are driven by alternating the flow through the coils forward/backward so you have two wires per coil. The 6-wire steppers are designed to have the center set to ground, then you energize the coil you want. The interface can be as simple as a 2N2222 transistor per coil. (Or larger MOSFET if more current is needed.)

a 6-wire stepper can also be driven as a 4-wire by not connecting the center lead and thereby using the entire coil. Again... use a bidirectional motor driver. (H-Bridge) to drive them.
audreyobscura (author) in reply to pattyshawFeb 18, 2012. 10:47 AM
Hey, if you Stepper motor has that many leads, I am guessing that you will have to connect it to an additional power source. Do you know the model number of the Stepper? If you do, I recommend seeking out the datasheet on the motor so that you know how much power you will need.
pattyshaw in reply to audreyobscuraFeb 19, 2012. 11:08 AM
It is a lin engineering 4118L-04 I believe it is a unipolar motor but i haven't been able to find its exact spec sheet
thesa1nt01 says: Feb 19, 2012. 12:14 PM
"Speed of the motor can be controlled by the amount of current reaching the coils from the battery to the commutator."

Should be changed to:

"Speed of the motor can be controlled by the amount of voltage applied to the coils from the battery to the commutator."

Voltage is proportional to speed and current is proportional to torque.
Arkyro in reply to thesa1nt01Feb 21, 2012. 5:00 AM
The speed of a DC motor can be controlled by limiting the current supplied to the commutator. Speed and Torque are inversely proportional.
throbscottle says: Feb 21, 2012. 12:23 AM
Really good instructable. Shame you didn't cover analogue DC motor control - I would have liked to read that since I've forgotten how it works...
Clemtasm says: Feb 20, 2012. 5:39 AM
I believe you mean speed of the motor can be controlled by controlling the amount of voltage across the motor?

My understanding is- A DC motor fed a constant voltage will have a fairly constant speed over a range of loads. A motor fed constant current will produce fairly constant torque over a range of speeds
dreadengineer says: Feb 19, 2012. 8:56 PM
The last paragraph is incorrect for stepper motors; I think you may have meant to put it in another section ("If you hook the battery leads of a stepper motor up to a battery, the axle will spin.").

To make a stepper spin, you have to use a microcontroller to pulse each of its coils in a sequence, as shown in your second picture. If you just hooked up a coil to a battery, the axle will be pulled into alignment with that coil and won't spin.
dakellymon says: Feb 19, 2012. 8:43 PM
Thanks for sharing.
didgitalpunk says: Feb 19, 2012. 12:53 PM
damn it where is that "like" button!
very good instructable!
askjerry says: Feb 19, 2012. 10:23 AM
Your Instructable is very good... but I didn't see where you mentioned using a driver chip or transistor to interface between the Arduino and the motor you are running. This may lead people to think they can just connect a motor directly tot he Arduino leads and run it directly. That is actually VERY BAD. The Arduino has limited current depending on the particular Atmel chip used for that model.

The Atmel is designed to only supply about 20mA per pin (0.020 amps)... enough to drive an LED or send a signal to another device. Servo motors are fine... the motor driver is built internally... but DC motors and Stepper motors are raw coils which...

a) Need a high current level. (Between 700mA to 4000mA)
b) Output a return spike when power is removed.
d) Pull more current through the core of the chip than it was designed to take.
e) Often require higher voltages, 12v, 24v, and 36v are common.

Sparkfun makes a suitable module that is completely assembled: http://www.sparkfun.com/products/10267

You can also purchase chips and roll your own if you like.
Here is one example:
http://search.digikey.com/us/en/products/E-L6219/497-1426-5-ND/585947

Another advantage to using a chip is that it supports MICROSTEPPING... so instead of 200 steps per revolution you can get 2000 or so. The chip pulses the coils with PWM (pulse width modulation) to allow for intermediate steps... and many chips will also throttle back the current when the stepper is not moving to help the motor run cooler and longer.

I hope that helps.
Jerry
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