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Drive a Stepper Motor (using IC STA401A)

To drive any unipolar stepper motor you need to consider the following.

1. Voltage rating

2. Current rating

3. Resistance of any one phase

once you know the voltage & current rating you can chose a driver IC which is capable of accommodating these specifications. In case you are not lucky enough to have the current rating and you only have resistance of any one phase then you can calculate the current rating by using the relationship mention below

V = I * R where V is voltage, R is Resistance and I is current.

This way of calculating the current rating may not give the entire details like stalling current etc. but with this calculation you can start driving the motor.

Here my main focus is to explain how to use IC STA401A module. let us say  I have a stepper motor with specifications as

Voltage = 5V

Current = 1 A

Step size = 1.8 degrees

Before using STA401A to drive the stepper motor you need to make sure that the driver IC can meet the requirements. Below are the steps to analyze the driver IC data sheet.

1. See whether the required ratings fall well below the absolute maximum ratings(voltage ,load current) of the IC.

2. Understand the the gain of the whole unit.

3. Understand weather it meets you frequency requirements (speed at which you would like to drive the stepper motor) .

4. Understand the temperature requirements( heat sink, if required).

Here is the circuit diagram which uses a micro controller along with stepper motor driver IC STA401A

The micro controller is assumed to give a TTL logic signal of 5 Volts as an input to STA401A module. The current provided through the micro controller to STA401A module is 5V/5000Ohms =0.001 Amps. The STA401A module has a gain( hfe) of 1000 hence the current sink through the module  from the stepper motor would be 1 Amp.

The stepper motor needs 5 watts to run and you also need to consider the efficiency of STA401A module. This understanding gives you an idea of how much power would be required from the power supply in order to drive the stepper motor.

Code for controlling a stepper motor is provided in the software section of this web site, please go through the link--> Code to control a stepper motor

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List of Topics --> Electronics

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Drive a Stepper Motor (using IC STA401A)

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Use Motor as Dynamo, Motor as a Brake, Dynamometer Test


List of Topics --> Software

Simple Program to Blink an LED (using embedded C language)

Code to Control a Stepper Motor

Code to Detect Obstacle using IR(Infrared) Sensor

Articles on C

Data types (under construction)


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