Stepper Motor Control - AVR Tutorial. Stepper motors pairs nicely with a smart device like a microcontroller to create precise digitally controlled movements that has made possible many of modern gizmos around us. For example a printer, scanner, plotters, fax, floppy drive (not so modern though!), automatic industrial machines like CNC (Computer numerically controlled) drills, laser shows etc. Though to a naked eye the motor of stepper look no other than a DC motor but the difference is that each step of a stepper motor is in control. For example a high speed desktop printer when the paper moves forward, to a novice it seems like a motor is just pushing the paper out but in reality the control board inside the printer request the motor to move the paper exactly same amount that has been printed. This precise movement keeps the next printed pixel in alignment with previously printed pixels. For example if you are making a robot, you want it to move exactly as per your program. Stepper Motor Controllers and other robot products. At RobotShop, you will find everything about robotics. Like if you say go forward 1. You cannot do this with DC Motors, because for it you need to calculate the exact speed for DC motor and then use blind timing for movement. Say if you happen to find out the your robot moves at 5cm per second then to move 1. So you keep the motor on for 2. But this can prove failure if the speed of robot changes due to drop in level of battery or some additional weight or simply due to an uneven terrain etc. So this method is not so trustworthy. The second method is the use of stepper motors.
Say you have a stepper motor of 7. Now if we assume you have attached a wheel of radius 3. I leave the math on you). That’s pretty decent. To move the motor forward 1. Instead if you step it 1. So now the bot is pretty much in your control. In the same way PCBs are drilled at accurate position, SMT components placed automatically at their desired location, pixel on a paper are printed. This is the first part of what will probably be two (or more) posts describing one of my latest projects – an Arduino Stroboscope based on the spindle motor of a. A Pololu stepper driver board is a well known RepRap machine stepper motor driver. The Pololu stepper driver boards are made as pluggable modules to a electronics. Below are some videos that may help you get the point. Types of stepper motor. Their are many types of stepper motors available but the two most common types are. Unipolar Stepper Motor– Has simple driver requirement. Less torque at same size and weight as compared to bipolar type. Bipolar Stepper Motor – Has slightly complicated driver requirement. More torque at same size and weight as compared to unipolar type. Since the Unipolar type is simpler to drive we will start our journey with it. Driving Stepper Motor with AVR MCUIn the figure below is shown a simplified construction of a stepper motor. The center is a permanent magnet(PM) rotor. Around it are four electromagnets. One end of all four electromagnet is connected to a point called . The common is usually connected to the stepper supply voltage (eg. The four coils are named A,B,C and D. To rotate a stepper motor, coils are excited in turns like A,B,C,D. The rotor will try to align itself with the currently exited coil. Lets say that the white point shown on rotor is magnetic north pole. Also assume that when coils are excited, their inner end becomes magnetic south. So the white point on rotor will try to align with the currently excited coil.(As the opposite poles attract)So to drive a stepper motor from AVR MCU you just need to excite the coils A,B,C,D in turns to rotate the motor in anti clock wire direction. If you want to rotate the motor in clock wise direction simply excite the coil in reverse order that is D,C,B,A. As the port of AVR can only sink or source 2. A current approximately, they cannot be used to drive the the coils directly. So we need some thing that can boost this current. The part that fit perfectly in this scenario is ULN2. A. It is a high voltage, high current Darlington array. It can be driven directly with a TTL level input and the output can source up to 5. Since it is array of seven darlington pair, (of which we require only four) it is much compact. In this example we will use PORTC to drive the stepper motor. So we connect PIN 1,2,3,4 of ULN with PORTC 0,1,2,3 of PORTC. The output is available on pin 1. ULN IC. These are connected to the four coils A,B,C and D of stepper motor. The common of stepper motor is connected to 1. The pin 8 of ULN2. IC is connected to GND (common of system). The whole connection can be made on a small bread board like this. Here I will present a small and simple library to drive a single stepper motor. The library supports port configuration that means you can change in which PORT stepper is connected. Their are only three function in the library. Stepper. Init()Must be called before calling any other stepper related function. This function configures the related PORT pins as output. Stepper. Step. CCW()Steps the stepper in counter clock wise direction. Stepper. Step. CW()Steps the stepper in clock wise direction. The library is provide in two files. These two files must be copied to current project folder and added to the AVR Studio Project. I am also providing a sample which demonstrate the use of above functions./******************************************************************************Title: Demo program to show the use of simple stepper library. Description: A unipolar stepper motor connected to PORTC0,1,2,3 via driver IC ULN2. A. This process is repeated as long as the board is powered. The code can be compiled using Win. AVR Compiler using the AVR Studio as front end. For more details on installing and using this tool please see the following tutorial. Compile the above program using AVR Studio (compiler is avr- gcc). And finally. burn the program using any ISP. Programmer to the ATmega. The fuse bits must be set as. High Fuse = C9 (hex value)Low fuse =FF (hex value)After burning the HEX file to MCU, finally you are ready to power up the setup. Videos for stepper motor control using AVRDownloads. Things Required. Help Us! We try to publish beginner friendly tutorials for latest subjects in embedded. If you like these tutorials and they have helped you. You can donate any amount. Credit or Debit Card or Paypal. We would be very thankful for your kind help. Subscribe! Don’t miss any article get them right in your inbox! Subscribe to our feeds powered by Feedburner. By. Avinash Guptawww. Avinash. Gupta. comme@avinashgupta. From Idea to Finished Product, Just Need One Tool - Easy. EDAFree Circuit Design Software: Start to Design your own PCB Easily. Cheapest PCB Prototype: Only $2 for 1. We are here to help! Post a help request. Stepper motor controller circuit and code. I build a step motor controller based on the schematics found on the Arduino Web site. First I try the 2 pins one for bipolar stepper motor. I wont be able to make it work, even less with the library available on the site. Maybe I’m dumb and I really dont understand something, but this circuit keeps both coils active at the same time. So I tried the second circuit, the 4 pins one. With the same library I wasn’t able to make it work either. So I create a piece of code of my own and I finally managed to make the motor run correctly. After that, I realize that I can merge the to circuits to possibly create a PWM abled bipolar motor controller with the L2. D. A somewhat bizzare idea, but I think it’s possible if we can program the Arduino to send 4 synced PWM signals. I’ll come back later (maybe never) with this thought. After some research I found that the TI DRV8. Allegro A3. 97. 7 are much more appropriate chips to do microstepping. But for now, there is my circuit. It’s advantage is that it can release the coils. Download the schematics (Fritzing format). The two PNP transistors are connected like the circuit proposed on the Arduino Web site. Plus, I use the enable pins. So my circuit needs four pins, and I don’t found a way to use less. Parts list. 1 x Arduino. L2. 93 Quadruple Half H- Bridge. K Ohm Resistors. 2 x 1. K Ohm Resistors. 2 x 2. N2. 22. 2 NPN Transistors. Bipolar Step Motor. There is the sequence to make the motor turn one direction, invert it to make it turn the other. Control sequence. CTRL AEN ACTRL BEN B0. There is my code to control the stepper motor. Like you see in my code I use direct port command to take less processor time. And I create a function called in the main loop for each steps. This way the code can do something else when the motor is running./*. Stepper Motor Controller. Kevin Filteau 2. 01. Playwithmyled. com. Motor controller pins. Some pictures of the prototype, the finalized circuit board (useful for the pinout) and a video taken while testing the circuit.
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