Stepper Motor Driver Circuit

Have you been searching for a goot damn circuit to drive your stepper motor?? Well even i did when i was learning robotics. Most stepper motor circuits that are available onlne have a bunch of transistors, Sometimes power trnsistors too quite a complicted circuit that drives you away far frm using it. Well i felt for most robotic use the stepper motor can be driven by a simple ULN2003 IC that costs just 12 bucks in my backyard.

The above are the most common types of stepper motors that you’l find in the market.

There are two types of stepper motor that normally is used.1)Unipolar 2)Bipolar . In simle terms they can be thought about like this. In unipolar there are 5 wires.One common wire and four wires to which power supply has to be given in a serial order to make it drive. Bipolar (not normally used in robotics) can have 6 wires and a pair of wires are given supplt at a time to drive it in steps.

STEP ANGLE :The angle with which the stepper motor turns for a single pulse if supply toone wire or a pair is called step angle.

Driving a stepper motor:

1) Identify the wire : Common and windings

As you may see that out of the five wires two are grouped as coomon. The other four are the windings you’l have to give your supply to. Now major crux here is to identify the common line. that’s pretty simple. Just take your multimeter and check the resistance between the wires. Hold one wire a common and it must bear a resistance of 75 ohms with all the other wires then that is the common wire.
Once you have done that the reset of the issue is just a cake walk.

Connect this circuit:

I guess you understand the connections: in case you find the fpic above messy have a look below,

So this is it.Now use your Microcontroller PIC16F877A to give +5v supply to pins a,b,c,d one by one that’s:

a=5v,b=0,c=0,d=0
a=0,b=5v,c=0,d=0
a=0,b=0,c=5v,d=0
a=0,b=0,c=0,d=5v
Then stand aside and watch your motor run.!!

A stepper motor is hard to make it usable in a robot yet the square type of stepper motor seememed to work pretty well for me. My Micoromouse Robot was built on stepper motor . I fount this mechanical design for a stepper mototr robo that’l help you design yours,have a look.

guys.. get your bot up and running

—Madan
If you are new to stepper motors and don’t get this clearly get the exact circut and code

P.S:-
–>Stepper motors are are mostly suited for contests where precession is most inportans like maze solving and path finding robots. where you’l need to know the distance you’d travelled or take a 90′ turn. these things are difficult to handle on a normal DC motor.

–>The minimum time between the two pulses given to ‘a’ , ‘b’ must be greater that 200 micorseconds(it depends on your motor)

–> Microcontroller can always be replaced with your computer parallel port

–> UlLN2003 can drain upto 500 mA so most stepper motors can be drivin satisfactorily.