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driver:stepper_basic [2024/06/24 20:21] – [NEMA standard for stepper motors] vamsandriver:stepper_basic [2024/06/24 21:30] (current) – [Stepper motor control with Arduino] vamsan
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 The standard also lists motors with faceplate dimensions given in metric units. These motors are typically referred to with NEMA xx, where xx is the diameter of the faceplate in inches multiplied by 10 (e.g., NEMA 17 has a diameter of 1.7 inches). There are further specifiers to describe stepper motors, and such details may be found in the ICS 16-2001 standard. The standard also lists motors with faceplate dimensions given in metric units. These motors are typically referred to with NEMA xx, where xx is the diameter of the faceplate in inches multiplied by 10 (e.g., NEMA 17 has a diameter of 1.7 inches). There are further specifiers to describe stepper motors, and such details may be found in the ICS 16-2001 standard.
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 ^Nema Type^NEMA 8^NEMA 11^NEMA 14^NEMA 17^NEMA 23^NEMA 34^NEMA 42| ^Nema Type^NEMA 8^NEMA 11^NEMA 14^NEMA 17^NEMA 23^NEMA 34^NEMA 42|
-^Frame Size ≈|20.3 mm \\ (0.79 in)|28 mm \\ (1.10 in)|35.6 mm \\ (1.4 in)|43.2 mm \\ (1.65 in)|58.4 mm \\ (2.3 in)|86.4 mm \\ (3.4 in)|106.7 mm \\ (4.2 in)| +^Motor Size ≈|20.3 mm \\ (0.79 in)|28 mm \\ (1.10 in)|35.6 mm \\ (1.4 in)|43.2 mm \\ (1.65 in)|58.4 mm \\ (2.3 in)|86.4 mm \\ (3.4 in)|106.7 mm \\ (4.2 in)| 
-^Motor Shaft Diameter|4 mm \\ 0.157 in|5 mm \\ 0.197 in|5 mm \\ 0.197 in|5 mm \\ 0.197 in|6.35mm \\ 0.250 in|9.5 mm \\ 0.375 in|16 mm \\ 0.625 in| +^Motor shaft diameter|4 mm \\ 0.157 in|5 mm \\ 0.197 in|5 mm \\ 0.197 in|5 mm \\ 0.197 in|6.35mm \\ 0.250 in|9.5 mm \\ 0.375 in|16 mm \\ 0.625 in| 
-^Bolt Hole Circle Diameter|22.6 mm \\ 0.891 in|32.5 mm \\ 1.280 in|36.8 mm \\ 1.448 in|43.8 mm \\ 1.725 in|66.7 mm \\ 2.625 in|98.4 mm \\ 3.875 in|125.7 mm \\ 4.950 in|+^Bolt hole circle diameter|22.6 mm \\ 0.891 in|32.5 mm \\ 1.280 in|36.8 mm \\ 1.448 in|43.8 mm \\ 1.725 in|66.7 mm \\ 2.625 in|98.4 mm \\ 3.875 in|125.7 mm \\ 4.950 in| 
 +^Bolt hole distance (square)|16 mm \\ 0.630 in|23 mm \\ 0.905 in|26 mm \\ 1.024 in|31 mm \\ 1.220 in|47 mm \\ 1.854 in|70 mm \\ 2.744 in|89 mm \\ 3.500 in| 
 +^Bolt Hole size|3mm \\ 0.118 in|4mm \\ 0.157 in|4mm \\ 0.157 in|4.40 mm \\ 0.173 in|5mm \\ 0.195 in|5.5 mm \\ 0.218 in|5.5 mm \\ 0.218 in| 
 + 
 +{{ :driver:nema_1.png?400 |NEMA standard for stepper motors}} 
 + 
 +===== Phase current waveforms ===== 
 +A stepper motor is a polyphase AC synchronous motor, and it is ideally driven by sinusoidal current. A full-step waveform is a gross approximation of a sinusoid, and is the reason why the motor exhibits so much vibration. Various drive techniques have been developed to better approximate a sinusoidal drive waveform: these are half stepping and microstepping. 
 + 
 +==== Wave drive (one phase on) ==== 
 +In this drive method only a single phase is activated at a time. It has the same number of steps as the full-step drive, but the motor will have significantly less torque than rated. It is rarely used. The animated figure shown above is a wave drive motor. In the animation, rotor has 25 teeth and it takes 4 steps to rotate by one tooth position. So there will be 25 × 4 = 100 steps per full rotation and each step will be 360⁄100 = **3.6°**. 
 + 
 +==== Full-step drive (two phases on) ==== 
 +This is the usual method for full-step driving the motor. Two phases are always on so the motor will provide its maximum rated torque. As soon as one phase is turned off, another one is turned on. Wave drive and single phase full step are both one and the same, with same number of steps but difference in torque. 
 + 
 +==== Half-stepping ==== 
 +When half-stepping, the drive alternates between two phases on and a single phase on. This increases the angular resolution. The motor also has less torque (approx 70%) at the full-step position (where only a single phase is on). This may be mitigated by increasing the current in the active winding to compensate. The advantage of half stepping is that the drive electronics need not change to support it. In animated figure shown above, if we change it to half-stepping, then it will take 8 steps to rotate by 1 tooth position. So there will be 25×8 = 200 steps per full rotation and each step will be 360/200 = **1.8°**. Its angle per step is half of the full step. 
 + 
 +==== Microstepping ==== 
 +What is commonly referred to as microstepping is often sine–cosine microstepping in which the winding current approximates a sinusoidal AC waveform. The common way to achieve sine-cosine current is with chopper-drive circuits. Sine–cosine microstepping is the most common form, but other waveforms can be used. Regardless of the waveform used, as the microsteps become smaller, motor operation becomes smoother, thereby greatly reducing resonance in any parts the motor may be connected to, as well as the motor itself. Resolution will be limited by the mechanical stiction, backlash, and other sources of error between the motor and the end device. Gear reducers may be used to increase resolution of positioning. 
 + 
 +Step size reduction is an important step motor feature and a fundamental reason for their use in positioning. 
 + 
 +===== Two phase stepper motors ===== 
 +There are two basic winding arrangements for the electromagnetic coils in a two phase stepper motor: bipolar and unipolar. 
 + 
 +==== Unipolar stepper motors ==== 
 +A unipolar stepper motor has one winding with center tap per phase. Each section of windings is switched on for each direction of magnetic field. Since in this arrangement a magnetic pole can be reversed without switching the polarity of the common wire, the commutation circuit can be simply a single switching transistor for each half winding.  
 + 
 +{{ :driver:unipolar_stepper_types.gif |Unipolar stepper motors}} 
 + 
 +Typically, given a phase, the center tap of each winding is made common: three leads per phase and six leads for a typical two phase motor. Often, these two phase commons are internally joined, so the motor has only five leads. 
 +==== Bipolar stepper motors ==== 
 +Bipolar motors have a pair of single winding connections per phase. The current in a winding needs to be reversed in order to reverse a magnetic pole, so the driving circuit must be more complicated, typically with an H-bridge arrangement (however there are several off-the-shelf driver chips available to make this a simple affair). There are two leads per phase, none is common. 
 + 
 +A typical driving pattern for a two coil bipolar stepper motor would be: **A+ B+ A− B−**. I.e. drive coil A with positive current, then remove current from coil A; then drive coil B with positive current, then remove current from coil B; then drive coil A with negative current (flipping polarity by switching the wires e.g. with an H bridge), then remove current from coil A; then drive coil B with negative current (again flipping polarity same as coil A); the cycle is complete and begins anew. 
 + 
 +Static friction effects using an H-bridge have been observed with certain drive topologies. 
 + 
 + 
 +===== Stepper motor drivers ===== 
 + 
 + 
 +===== Stepper motor control with Arduino ===== 
 + 
 +{{ :driver:arduino_stepper_1.png?400 |Stepper motor control with Arduino}}
 ===== Sources ===== ===== Sources =====
 https://www.moonsindustries.com/c/stepper-motors-a02 \\ https://www.moonsindustries.com/c/stepper-motors-a02 \\
 +https://en.wikipedia.org/wiki/Stepper_motor \\
 +https://circuitdigest.com/electronic-circuits/stepper-motor-driver \\
 +