Wednesday, January 22, 2020

Torque vs Speed Characteristics of Steping Motor

The Speed-Torque graph indicates the characteristic relationship between the speed and torque when the stepping motor is driven. The torque vs speed characteristics are the key to selecting the right motor and drive method for a specific application. These characteristics are dependent upon (change with) the motor, excitation mode and type of driver or drive method. On the graph, the horizontal axis is the speed at the motor’s output shaft while the vertical axis is the torque.

Torque vs Speed Characteristics of Steping Motor

1.Maximum Holding Torque

The holding torque is the maximum holding power (torque) the stepping motor has when power (rated current) is being supplied but the motor is not rotating (with consideration given to the permissible strength of the gear when applicable).

2.Pull-in Curve
The pull-in curve defines a area refered to as the start stop region. This is the maximum frequency at which the motor can start/stop instantaneously, with a load applied, without loss of synchronism.

3.Pullout Torque Curve
Pullout torque is the maximum torque that can be output at a given speed. When selecting a motor, be sure the required torque falls within this curve.

4.Maximum Starting Frequency
This is the maximum pulse speed at which the hybrid stepping motor can start or stop instantaneously (without an acceleration or deceleration time) when the frictional load and inertial load of the stepping motor are 0. Driving the motor at greater than this pulse speed requires gradual acceleration or deceleration. This frequency drops when thereis an inertial load on the motor.

5. Maximum Slew Rate

The maximum operating frequency of the motor with no load applied.


Saturday, January 4, 2020

A Simple guide to identify the stepper motor you have

You’ve got your stepper motor from Ebay, the manual is in Chinese and you don’t have a clue if the motor is unipolar or bipolar.

Summarizing quickly.
If 8 wires, it will probably be unipolar 8 wires stepper motor, 4 per coil.
If 6 wires, probably unipolar, 3 for one coil and another 3 for the other. This means each coil has its own ground.
If 5 wires, probably also unipolar. 2 for one coil, 2 for the other and a common ground for both coils.
If 4 wires, probably a bipolar 4 wires stepper motor, 2 cables per coil.
I’ve also found this video which can help you differentiate the motor type you’ve got:

A Simple guide to identify the stepper motor you have

Wiring the stepper motors.
This will be a guide to connect the most common stepper motors for 3D printers. They usually mount NEMA17 with 4 wires.

Quick version.
If the motor comes with coloured wires, the typical colours are Red/Blue/Green/Black
Issues: It is not guaranteed to be like this! Who knows where the motors come from, how are they wired, etc. I’ve known many people who were not able to make them work and at the end, they realized the problem was in the wiring.

Longer version
The most common drivers which the 3D printers and home machines use are bipolar. The most known drivers for bipolar motors are pololus a4988 and DRV8825.
The motor will have 4 wires. 2 per coil, therefore what we have to figure out is which ones are the coils.

Figure out the coils
If we are going to wire a stepper motor, we have to figure out which wires belong to which coil.
We can name them coil A and coil B, or coil 1 and coil 2.
Luckily, the drivers designers decided to use both systems (/ironic)
If you read the driver’s label, the DRV8825 specifies A2 A1 B1 B2 and the A4988 specifies 1B 1A 2A 2B.
Just read it several times, and make sure you understand it is exactly the same.

Size and NEMA standard of Stepper Motor You Should Consider

Introduction to the functions and troubleshooting of closed-loop stepper motor drivers

1.Overview A closed-loop stepper motor driver is a motor driver that integrates multiple functions such as speed regulation, positioning, i...