Saturday, October 27, 2018

How to Choose A Suitable Rotation Speed Stepper Motor

While we chose a stepper motor online supplier , according to the speed, it is very to choose a motor working at the best situation. The stepper motor speed divided into :working at low speed, working at a more than 2000rpm speed and working at a wide range from low speed to high speed. The choice of stepper motor will be different.

While operated at a high speed, because of the influence of circuit inductance, the flow of the circuit current will be limited. Assuming that the coil reactance of the 1 phase is X, the frequency angular velocity of the driver current is w(electric angle), Its synchronous rotating rotor mechanical angle is wm, at high speed, the coil resistance R<<X, the impedance Z of the 1-phase winding becomes the following:

Z≈wL=NRwmL  (5)
How to Choose A Suitable Rotation Speed Stepper Motor

When the rotor rotates at the rotation speed wm, the impedance Z requires that the number of teeth N of the rotor is as small as possible so that the current easily flows. In addition, the stator is driven by a constant current. If the rotational speed is too high, the cross-flow control cannot be achieved, and it will become a constant-voltage drive. When the rotation speed is high, this state is often driven. In this state, when the applied voltage is V, if The electromotive force is E, then its current I is determined by the following formula:

İ=(V(.)-E(.))/Z      (6)


Figure 5.1 Equivalent circuit when rotating at high speed

The current I of the motor with small Nr rotation speed is large. The step angle is determined by the formula θs=π/PNr. If the number of gears Nr is small, the step angle of the stepping motor is large. When operating at high speed, select a stepper motor with a large step angle. On the contrary, it is more appropriate to drive a motor with a small step angle at a low speed.

Low-speed operation tends to produce vibration or resonance. In order to avoid or reduce vibration, the step angle of the motor is small, and the two-phase motor is not as good as the three-phase motor. Further analysis, full stepper motor is not as good as half stepping and stepping. In addition, a motor with a large number of rotor gears has a large torque at a low speed. When using at low speed, use direct drive as much as possible without using a reducer. This is because a stepper motor with a small step angle has a high speed-to-torque characteristic and a large drop in slope at low speed, which is suitable for low-speed operation.

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Tuesday, October 23, 2018

Which is better? Servo motor or stepper motor?

The overwhelming majority of linear motion applications (with the exception of pneumatically-driven types) use either a stepper motor or a servo motor to provide torque to the driving mechanism, which is typically a ball or lead screw, rack and pinion, or belt and pulley system. And unlike other components involved in linear motion, when choosing a motor, there is usually a clear answer to the question, “Which technology should I use?” This is because servo motors and stepper motors are designed for very different performance characteristics. Determining which is to use for a given application requires understanding these differences and balancing them with other factors, such as cost and complexity.

The basic premise of a servo motor is that it operates in a closed loop motor system, meaning that an encoder or feedback device sends signals to the controller indicating the actual position of the motor. This information is compared against the commanded position, and the controller sends corrective signals to the motor in order to minimize the error. The result is very tight positioning accuracy and more reliable positioning than can be achieved with stepper motors. However, closed loop systems require tuning of the control parameters and are more time-consuming to set up. The additional components required for feedback and greater complexity also make them more expensive than steppers.

A general rule is that stepper motors are best suited for applications that run at 1000 rpm and below. This is because at higher speeds, a stepper motor’s torque production drops off rapidly. Servo motors can operate at a wide range of speeds, and they’re usually the better choice for high-speed applications.

As mentioned earlier, a stepper motor rapidly loses torque capability as its speed increases, with torque typically falling off at speeds above 1000 rpm. However, at lower speeds, steppers have excellent torque-producing capability for a given motor size. It’s important, however, to never exceed a stepper motor’s rated torque (which can limit its ability to accelerate), because doing so can result in lost steps or cause the motor to stall.

Which is better? Servo motor or stepper motor?

The verdict
In general, servo motors are the better choice for applications that require precise and accurate positioning, high speeds, and/or the ability to withstand changing loads (especially those that might require higher than the rated motor torque). For applications that don’t require position feedback and that operate solely within the design limits of the motor, stepper motors from china provide a simpler, more cost-effective solution.

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Friday, October 12, 2018

NEMA 11 Stepper Motor dual shaft 0.67 Amps Description

This is the smallest stepper motor we've featured to date, but it still packs a nice punch in a compact, rectangular NEMA 11 form.

NEMA 11 Stepper Motor dual shaft 0.67 Amps

This micro stepper motor is small enough to fit in the palm of your hand but still features 16.7 oz-in of holding torque. These NEMA 11 or nema 14 stepping motors are perfect for small CNC machines, 3D printers, laboratory assistance, linear actuators, telescopes, pick and place machines, and prototyping machines. Single shaft .187 inch (4.75mm)

Technical Specifications:
1.8 degree stepping angle (200 steps/revolution)
Rated Voltage: 6.2V
Current/Phase: .67 A
Resistance/Phase: 9.2 ohms
Inductance/Phase: 5.7mH±20%(1KHz)
Holding Torque: 16.7 oz-in / 1200 g-cm
Number of Leads: 4
Rotor Inertia: 18 g-cm2
Weight: 0.44 lbs / 0.2 kg
Length: 50.5 mm

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