Stepper Motor Driver

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May 05, 2014 With 2 driver chips and 4 full H-bridges total, each shield can drive up to two stepper motors. The driver chips are interfaced via a dedicated PWM driver chip with an I2C interface. This frees up lots of GPIO pins for other uses, and makes the shield stackable too. You can stack up to 32 of them to control 64 motors with just 2 IO pins!

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What is a stepper motor driver?

A stepper motor driver is an electronic device that is used to drive the stepper motor. By itself it usually does nothing and must be used together with a controller like PoKeys57CNC.

There are a lot of different types of stepper motor drivers but in general all do the same thing – move stepper motors.

Each stepper motor and driver combines a stepper motor selected from various types, with a dedicated driver. Drivers that operate in the pulse input mode and built-in controller mode are available. You can select a desired combination according to the required operation system. Step Motor Drives. Step motor drives from Applied Motion Products offer unparalleled performance for today's modern machine builders. From the ground up these drives offer best-in-class current control for optimal smoothness and torque, robust and flexible on-board control options, and industry-standard industrial network communications.

Why do I need one?

Stepper motors require voltages and/or currents that the controller simply can’t produce. Therefor we need to use a stepper motor driver. This electronic device will transform our movement instructions from a controller in to a sequence where the winding in stepper motor will be turned on or off while still providing enough power to it.

All of this can of course be produced by a microcontroller driving a few FETs but the design and the programming would take time. Thankfully there are already made solutions.

Types of drivers

In general there are two types of drivers. The constant voltage drivers (L/R drivers) and constant current drivers (chopper drivers).

constant voltage drivers (L/R drivers):
- they are cheaper than constant current drivers
- use voltage to produce torque
- usually not efficient
- worse performance than chopper drivers
constant current drivers (chopper drivers):
- more expensive
- more complex circuits
- use constant current to produce torque
- much better performance than the L/R drivers

The constant current drivers are almost always used since there are many ICs available and offer much better performance. You can find integrated circuits which already have integrated FETs, these are usually meant for lower currents (up to a couple of A) since they are small and heat dissipation could be a problem. Another type uses external FETs and the maximum current is only limited by the external FETs used.

For example the PoStep25-32 uses an integrated circuit which has integrated FETs and can provide up to 2.5A unlike the PoStep60-256 which uses external FETs and can provide up to 6 Amps.

Microstepping

Stepper motors move in steps which is usually 1.8°,that is 200 steps per revolution. This can be a problem when we need small movements. One option would be to use some kind of transmission but there is also another way – microstepping. Microstepping means that we can have more than 200 steps per revolution and in turn have smaller movements. This option is already integrated in most ICs and can be configured by simply moving a jumper like on PoStep25-32.

When driving stepper motors with full steps the output of the stepper motor driver looks like a square signal and produces rough movements. The bigger the microstepping the more the output signal looks like a sine wave and the stepper motor moves more smoothly. But there is a downside to this. With increasing microstepping value the torque drops a quite lot and if the value is too great it could happen that the motor can’t produce enough torque to even turn. Usually 1/4, 1/8 or even 1/16 can produce satisfactory smooth movements while still producing enough torque.

The following image shows how the output changes when selecting different microstepping values. You can see that the output looks increasingly more like a sine wave.

So what do these values even mean?

Microstepping tells us how many micro steps should a stepper make to produce one full step. The 1/1 value tells us that the stepper must make one microstep to produce one full step (so there is no microstepping). Value of 1/2 is called a half step and tells us that the stepper motor must make 2 microsteps for one full step. This means that the stepper motor should make 400 steps for one full revolution. A value of 1/8 will tell us that the motor should make 8 microsteps for one full step and 1600 steps for one full revolution. The same principle applies for all of the microstepping values.

How to drive the stepper motor driver

Most stepper motor drivers have a step/dir input. This means there are only two signals needed for each driver. The step signal is used for making steps and looks like a PWM signal. Each pulse means that the stepper will move for one step (or microstep). The dir signal means direction and is used to signal in which direction (CW or CCW) will the stepper turn.

Conclusion

We have found out that the stepper motor driver is a must have if our design requires the use of a stepper motor since the controller can’t produce enough current and enough high voltage. There are different types but the chopper drivers offer the best performance. Also the microstepping offers a great solution at first sight but produces a problem of decreased torque. It is still extremely useful but must be used properly. There are a lot of different ICs available for driving the stepper motor and many already made solutions like PoStep25-32 and PoStep60-256 which provide plug and play solution and are easy to use.

And if you would like to learn more here is a great starting point.

p.s.: Article about stepper motor driver was SEO optimized with the help of slovenian SEO freelancer Seo-Praktik.si.

Introduction

A Stepper Motor Driver is a circuit or device that provides the necessary current and voltage to a Stepper Motor so that it has a smooth operation. A Stepper Motor is a type of DC Motor that rotates in steps.

The main difference between a simple DC Motor and a Stepper Motor is that through a Stepper Motor, we can achieve precise positioning with the help of digital control.

A Stepper Motor rotates precisely by synchronising the pulse signals from a controller, which are given through a Driver. A Stepper Motor Driver is a circuit that takes the pulse signals from a controller and converts them in to Stepper Motor Motion.

In this project, we have designed a simple 12V Stepper Motor Driver Circuit using 555 Timer IC (acting as a controller), a CD4017 Decade Counter (acting as the driver) along with few other components.

Circuit Diagram

Components Required

555 Timer IC
CD4017 Johnson Decade Counter (10 Decoded Outputs)
4 x 2N2222 NPN Transistors
4 x 1N4007 PN Junction Diodes
4 x 1 KΩ Resistors (1/4 Watt)
2.2 KΩ Resistor (1/4 Watt)
470 Ω Resistor (1/4 Watt)
100 KΩ Potentiometer (Knob type)
100 pF Ceramic Disc Capacitor (Code – 101) (Also read as 0.1 nF)
1µF 16V Polarized Capacitor
12V Stepper Motor (Unipolar – 5 Wire)
Connecting Wires
Breadboard (Prototyping Board)
12V Power supply

Component Description

555 Timer IC

IC 555 is a very famous timer IC that is often used for time delays, pulse generation and many oscillator applications. IC 555 has three modes of operations namely Astable Multivibrator (Pulse Generator), Monostable Multivibrator (Time Delays) and Bistable Multivibrator (Flip – Flop). In this project, we have used this 555 IC for generating a pulse i.e. in Astable Mode of operation.

CD4017 Decade Counter IC

CD4017 is a Counter IC that produces 10 Decoded outputs and hence a Decade Counter. These counters are often used in displays, frequency division operations, binary counters, etc.

But in this project, we are using the CD4017 Counter IC as a Stepper Motor Driver. And hence, this Stepper Motor Driver Circuit is essentially a Binary Counter Circuit.

Stepper Motor

A 12V Stepper Motor is used in this project. It is a Unipolar type Stepper Motor with 5 – wire configuration. Basically, Stepper Motors are classified in to Unipolar Stepper Motors and Bipolar Stepper Motors, based on the windings of the stator. The following image shows a Bipolar Stepper Motor with its winding.

The Driver circuit for a Unipolar Stepper Motor can be constructed with the help of few transistors or a Darlington Transistor IC like ULN2003.

Tomodachi life 3ds rom download. But, the driver circuit for a Bipolar Stepper Motor requires an H – bridge type connection. Hence, we use H – bridge ICs like L293D to drive Bipolar Stepper Motors.

Circuit Design

We will start with the Square wave Generator i.e. 555 IC in Astable Mode. A 2.2 KΩ Resistor is connected between the VCC and Discharge Pin of 555 (Pin 7).

A 100 KΩ Potentiometer is connected between the Discharge Pin (Pin 7) and the Threshold pin (Pin 6), which is in turn shorted with the Trigger Pin (Pin 2).

A 1 µF Capacitor is connected between the Trigger pin (Pin 2) and GND. A Bypass Capacitor of 100 pF is connected at the Control Voltage Pin (Pin 5). The other pins i.e. VCC (Pin 8) is connected to 12V supply, Reset Pin (Pin 4) to 12V supply and Ground Pin (Pin 1) to GND.

The Output of 555 Timer IC i.e. the Pin 3 is given as Clock Input to the CD4017 Counter IC i.e. to its 14th Pin. The VDD and VSS pins of CD4017 i.e. Pin 16 and 8 are connected to 12V Supply and GND respectively. Enable Pin (Pin 13) is connected to ground.

We need to control the 4 coil terminals of two coils in the stepper motor. Hence, we need only 4 outputs from the driver. These outputs are Q0 to Q3 i.e. Pins 3, 2, 4 and 7 respectively. The outputs of the Counter are connected to base terminals of 4 transistors through separate 1 KΩ Resistors.

The counter must reset on the fifth pulse and hence the Q4 (Pin 10) which in nothing but the fifth output, is connected to the reset pin of CD4017 i.e. pin 15 and this pin is connected to GND through a 470 Ω Resistor.

The Stepper Motor is a Unipolar Type in 5 wire configuration. The center pin is shorted internally and is connected to the supply (12V here).

The other 4 terminals of the stepper motor are the ends of two coils. They must be connected to the collector terminals of the four transistors.

It important that they are connected in the sequence of firing of the outputs. Finally, four diodes are connected between the collector terminals and supply. Diodes are very important as they will protect the transistors from inductive spiking.

Working of the Stepper Motor Driver Circuit

The working of this Stepper Motor Driver circuit is very simple. We will see a step – by – step working explanation.First, the 555 Timer IC is configured as an Astable Multivibrator i.e. it acts as a square wave generator.

Based on the position of the Potentiometer, the frequency of the square wave will vary anywhere between 7 Hz to 340 Hz.

This square wave is given to the CD4017 Counter IC as its Clock Input. For every positive transition of the clock signal i.e. a low to high transition, the counter output advances by one count.

For first positive transition on clock, Q0 will be high, for second positive transition, Q1 will be high and so on.

Since we need only 4 outputs, the fifth output i.e. Q4 is connected to the Reset pin so that the counter will reset and the counting starts once again.

The outputs of the Counter IC CD4017 are given to 4 different transistor, which are in turn connected to the 4 coil terminals of the Stepper Motor. We can understand better from the following diagram.

Assume the points A, B, C and D are the contacts of the coils connected to the transistors. The common wire in the stepper motor is given to 12V supply./return-to-castle-wolfenstein-download-ita-pc.html.

When the first clock signal is applied to the CD4017, Q0 becomes HIGH. This will turn ON the corresponding Transistor.

As a result, the supply from the common wire goes through point A to ground. This will energize the coil and acts as an electromagnet. The rotor will get attracted and turns to that position.

During the second clock pulse, output Q1 become HIGH and as a result, the transistor associated with it is turned ON. Now, the current flows from common wire to GND through point B.

Hence, this coil will be energized and turns in to an electromagnet. This will further rotate the rotor. This process continues and depending on the frequency of the clock signal, the speed of rotation of the stepper motor varies.