# Tag Info

35

The two are largely the same, fundamentally. However, they differer in intended application. A stepper motor is intended to be operated in, well, steps. A BLDC motor is intended to be operated to provide smooth motion. Since stepper motors are used for motion control, repeatability of the steps is desirable. That is, if you start at one step, then to ...

24

The main point of a stepper motor is that you get discrete steps. However, the cost is larger size and lower efficiency than a continuous motor of the same torque. Stepper motors also have a low upper speed. The advantage of discrete steps can outweigh the various disadvantages when the system can be controlled open loop. If you're going to provide ...

15

I'll give you some advice, but the first thing you need to do is be aware that you're trying something that may well be beyond your abilities. .03 degrees (1/2 milliradian or 2 minutes of arc) requires a great deal of care, and probably access to a good machine shop. In order: 1) You are correct to be leery of microstepping. It simply will not give you the ...

14

A microcontroller has a very low output current. You shouldn't drive directly more than an usual indicator LED with it. The motor draws a much higher current. Connecting directly will result in not working motor and destroying the microcontroller due to high currents. Drivers are not used only for motors. They are used for any device that usually draws ...

13

There is a lot of noise in the answers to this question that seem to be conflating "servo motor" as a generic term for variety of closed-loop feedback servo systems, and "servo motor" as used basically exclusively within the RC model community. Note that "servo motor" does NOT specifically refer to the pulse-duration-controlled potentiometer-feedback non-...

13

This is not actually particularly rare. In industrial systems, stepper motors with encoder feedback are relatively common. And for hobbyists, there is e.g. the Mechaduino project. There are several benefits to using feedback with stepper motors: Does not lose position when overloaded. Can handle higher torque loads, because the feedback keeps magnetic ...

12

Using dimensional analysis, and cancelling out units (i.e., "dimensions") just like they are numbers, gives you a clear answer: $$\frac{1 \ step}{pulse} \ \times \frac{5000 \ pulse}{1\ sec} \times \frac{1.8 \ degrees}{1 \ step}\times \frac{1 \ revolution}{360 \ degrees}\times \frac{60\ sec}{1\ min} = \frac{1500\ revolution}{min}$$ step, pulse, sec, ...

11

Many home made pick and place machines are very similar to CNC milling machines, and this is where you should take your inspiration from. The machine consists of three linear axes, each of which consists of: some kind of linear bearing or rail to allow the axis to slide freely. some kind of motor to actuate the movement. These two parts will probably make ...

11

In SPI each bit is transmitted on a clock edge, therefore the data rate (in bits) is the same as the clock frequency. Your datasheet is not providing the maximum frequency, but it is providing the minimum cycle time, which is $250ns$. As we know the relation between frequency and period time is $f=1/T$, we can calculate the maximum frequency as f_{max}... 11 Fix a lever of a precise known length to the specimen and add calibrated masses. Measure the deflection with a dial gauge. Perpendicularity might be a concern and could be addressed with geometry... However, the error that introduces is probably small compared to other sources. The sources of errors may well be worth checking. I know that for the ... 10 (Your bipolar 4 wire motor?) Current through 1a, 1b coils will turn the rotor so it is aligned as shown above. Turn on the current (in the appropriate direction) the rotor turns clockwise (half step) between 1a, 2a. Turn off the current to 1a, 1b and the rotor turns clockwise (another half step) to align with 2a, 2b. Reversing the direction of the current in ... 9 It says on the Murata data sheet (under the maximum ratings) that The outputs are not intended to accept appreciable reverse current. This is a warning not to allow anything on that output that can raise the voltage and feed back power to the device. The L6470 is a H bridge device using mosfets - the mosfets protect themselves by routing energy from ... 9 Holy cow. That's a real load for a little motor like yours. The problem is not weight, but moment of inertia. If you're going to do this stuff, you need to figure out how to calculate this. First, moment of inertia. For a disk of mass M and radius R,I_z = \frac{MR^2}{2} = \frac{(13.6 \text{ kg})({.43\text{m})^2}}{2} = 1.3 Since the nominal torque T of ...

9

There are "hollow shaft motors" similar to these. The inside of the shaft can be threaded (or a nut can be fitted inside) to make the motor itself travel along a matching threaded rod.

9

Provided you don't miss a step, a stepper motor should give you a deterministic movement. You can run it N steps forwards and N steps backwards and it will be in the same place. This is because the steps are discrete. Problems arise if it jams or you try to drive it too fast. Many systems have a simple means of resetting to a known state through a limit ...

8

You have a third type of motor: A "Universal" motor. This is a motor can can be configured as either a unipolar or a bipolar motor. General rules: 4 Wires: Bipolar only 5 Wires: Unipolar only 6 Wires: Universal 8 Wires: Universal A unipolar only motor has the center of both windings connected together internally. This precludes the use of the motor in a ...

8

I would recommend a stepper motor plus worm drive. You will be able to keep this perfectly still, which is what you want for a camera. A servo motor contains a circuit which actively tries to maintain the position of the motor. This system can be affected by external forces, electrical noise from the angle sensor, and poor tuning of the control algorithm. ...

8

BJTs tend towards either amplification (Ic increases with Ib) or switching (Ic is on, or off). Amplifier transistors have good gain linearity, but DC gain is moderate, and switching time and Vce(sat) may not be very low (e.g. the 2n5550). Switching transistors have very fast switching time, high DC gain and low Vce(sat) but gain linearity is not much of a ...

8

While the other current answer to this question quotes a comprehensive enough answer courtesy WikiPedia, here is a simplified TL;DR: Stepper motor: Moves in steps, with a fixed number of steps per revolution. Thus, controllable across any number of revolutions, in jumps of the step size. Could be unidirectional or bidirectional. Each step is exactly the ...

8

The datasheet you cite is for a linear actuator, which is the combination of a stepper motor and a leadscrew. In order to convert from linear to angular measure, you would need to know the thread pitch (how far it moves in one rotation) of the leadscrew.

8

When the controller steps the motor, the rotor has to move far enough (angle) that when the next coil (or coil pair) is energized it will pull the rotor in the correct direction. If the rotor has not moved through enough angle, then the coils will pull the rotor backwards and the motor just sits there and buzzes. You can find many illustrations and ...

7

Is your project the stepper motor driver, or is this for another, larger project? Unless you specifically want to learn about the intricacies of driving stepper motors, I would recommend just buying an off-the-shell stepper driver, either in IC form, or completely assembled. I'm a big fan of the Allegro Micro stepper drivers. If you want a simple, off-...

7

If your stepper has six wires, it can be used as a unipolar motor because you have 2*3 wires, where one of the three wires (each) is a center tap and the other two wires are one or another end of the same winding started at this center tap. Please see the appropriate section of the wikipedia article about steppers. Bipolar motors have four wires; two for ...

7

What you're looking for is called a Trapezoidal velocity profile. There is no need to use sin waves. Smooth motion can be achieved by simply linearly ramping up the velocity to its maximum, holding it there, then letting it ramp down again. Many CNC milling machines and robots use this type of profile. If you want super smooth motion, you can go for an S-...

7

The A4983 stepper driver has internal diodes which will shunt any excess power back into the supply rails (the internal mosfet body diodes), which means that if the motors are back driven and there is no dynamic braking/load dump then the supply rails will climb until something blows up. The most common ways to deal with this is to both add lots of bulk ...

7

If speed and acceleration aren't a problem, then there are two other mechanical performance issues you need to get right. One is the torque. You should measure the amount of torque required to turn the dials on your lathe while making its deepest cut into steel. You're a mechanical engineer, I'll leave you to think of a way to measure it. Take a look at the ...

7

One important factor when working with stepper motors is hold torque. You can do some simple calculations based on your camera weight and platform radius to determine the torque due to gravity, and your hold torque should be a fair about larger than that or the motor will slip. You'll also need stepper motor drivers in order to control the motors and ...

7

A stepper motor is a form of brushless DC motor, but with a specific physical arrangement of coils and stator so as to achieve a fixed number of stops or detents subdividing the full circle of rotation. The number of poles of a stepper motor determine the step size or number of subdivisions, or "full steps", if you like. However, with some fancy footwork ...

7

The TC4422 is a MOSFET gate driver and is not really intended to drive motors. The internal resistance is 6.3 ohms typically (could be 50% more when hot), so your current is being limited by the driver to not more than a couple amperes. You'll note that 18V/6.3 ohms is about 3A, so that's about the current you can momentarily get from it with maximum ...

7

The diodes are meant for absorbing voltage spikes above M+ and below GND. They have to have low voltage drop to start conducting sooner then the built-in diodes. As the message says, they have to be connected between output and power rails, like this (ignore the depicted buffer): (source: radio-electronics.com) Edit: The diodes should be wired like this:

Only top voted, non community-wiki answers of a minimum length are eligible