Month: October 2018 (Page 2 of 2)

nema 23 stepper motor: it’different from servo motor

nema 23 stepper motor and servo motor is different in following 5 aspects.
1. low frequency characteristics are different, nema 23 stepper motor is prone to low frequency vibration phenomenon at low speed, when it works at low speed, generally use damping technology or subdivision technology to overcome low frequency vibration phenomenon, servo motor runs very smoothly, even at low speed There will be vibrations.
2. The moment frequency characteristics are different, the output torque of nema 23 stepper motor will decrease with the increase of the speed, and the servo motor will be the constant torque output.
3. The running performance is different, the control of nema 23 stepper motor is open-loop control, the starting frequency is too high or the load is too large, easy to lose step or block the phenomenon, the over-speed is easy to occur when the speed is too high, the servo drive system is closed loop Control, the driver can directly sample the motor encoder feedback signal, internal position loop and speed loop, generally no stepper motor over-step or overshoot phenomenon, the control performance is more reliable.
4. The speed response performance is different, nema 23 stepper motor needs hundreds of milliseconds from the standstill acceleration to the working speed, and the servo system has better acceleration performance, generally only a few milliseconds, and can be used in control occasions requiring fast start and stop.
5. The overload capability is different, nema 23 stepper motor generally does not have overload capability, and the servo motor has strong overload capability.

nema 23: what’s the advantage of it

Nema 23 consists of a rotor with permanent magnets and a fixed stator with a winding. When the current flows through the stator winding, it generates a flux distribution that interacts with the rotor’s magnetic field distribution to exert a steering force.
Nema 23 has high magnetic pole counts, usually 50 or more. The stepper motor driver charges each pole in order, so that the rotor rotates in a series of increments or steps. Because the poles are very high, the motion seems to be continuous.
Nema 23 has many advantages. Because they generate incremental motion, they usually run open-loop, eliminating the cost and complexity of encoders or parsers. The high pole count allows them to produce very high torque at zero speed. They are compact and economical.
In adverse aspects, nema 23 has speed limits. They usually run best at 1200 rpm or below. Although they produce high torque at zero speed, the torque decreases with the increase of speed. For example, a motor that produces 100 ounces of inches at zero speed may produce only 50 ounces of inches at 500 rpm and only 10 ounces at 1000 rpm. If nema 23 is used to drive ball screw actuators or similar, it may not provide enough speed to meet the needs of the application.

stepper motor driver: what is it used for?

stepper motor driver circuit is a circuit that makes the stepper motor run smoothly by providing the necessary voltage/current.
One point to note in stepper motor positioning is that the positioning of the stepper motor is precisely achieved with the help of digital control. The stepper motor rotates by the pulse signal of the drive circuit synchronization controller. The stepper motor driver receives pulses from the controller and converts them into stepper motor rotation.
A stepper motor driver is a brushless motor that operates on a pulsed current. In a pulsed current, each pulse causes a rotor to rotate to a fully rotated portion. Servo motors are generally suitable for a wider range of applications, especially when precise motion is required, but stepper motors may be a useful alternative, depending on the application.
Stepper motor drivers are robust, economical and very suitable for digital drives and applications without closed-loop feedback. They are usually used for rotating hard drives, printers, robots, CNC machines, and so on.
The basic elements of the stepper motor drive circuit are:
1. Controller (microcontroller or microprocessor)
2. Driving chip for controlling and processing motor current
3. power supply device
4. All kinds of equipment, such as radiator, switch and so on.
Note: the establishment of stepper motor driver is more to choose the right power supply and driver, and the choice of microcontroller is secondary.

nema 34 stepper motor: how to get the feedback

nema 34 stepper motor is a hybrid stepper motor, it is available in different lengths to suit different applications. In this article, we are going to talk about how can we get feedback from a nema 34 stepper motor.
Usually we use CTs to check the state of nema 34 stepper motor, but stepper motor is usually small DC motor, Hall effect sensor can not be very good telescopic. Another way to use automation is terminal switches. Rotary actuators usually have a set of NO / NC contacts that change state at preset angles (such as 5 or 85 degrees). Some also provide analog output back to your controller, so in the initial command 10Vdc to the analog input terminal, the actuator will produce a steadily rising analog output back, depending on the actuator’s current position as it rotates to full.
So the series of cams on the output shaft of the Nema 34 stepper motor and the instantaneous roller switches spaced around it will give you a set of binary shaft positions as feedback.
Do you want a more fluid analog? You can also set up an IR transceiver aligned with the reflector on the output axis and use counter IC or accumulator logic to determine the number of rotations or the speed of rotation. In particular, add a gradient to the IR reflective band of the rotating shaft, then the IC can now tell you the current shaft position and rotating speed of nema 34 stepper motor.

nema 23 stepper motor: important factor for a CNC machine

Nema 23 stepper motor is widely used in CNC machine. As we know, when it comes to providing power for CNC machine, the core and soul of the machine is the stepper motor. The speed, accuracy and accuracy of CNC router depend on the size and type of the stepper motor. Nema 23 stepper motor and servo motor are two primary motors used in CNC machine.
Two CNC stepper motors are priced very well, but nema 23 stepper motors are usually priced less. Even if the servo motor and the stepper motor have the same power level, the price of nema 23stepper motor is often lower. Stepping motors are easier to find and make them richer.
nema 23 Stepper motors are incredibly versatile, making them very popular with enthusiasts and industrial applications. Stepper motors can be found in thousands of products from personal computers to automobiles.
Nema 23 stepper motors are more reliable than servo motors because they do not require encoders. Servo motors are also very reliable, but they need an encoder that is known to fail.
Life span – stepper motor is also considered to be a brushless motor, in which servo is brushed. The brush must be replaced every 2,000 hours after operation, because the only possible wear and tear component on nema 23 stepper motor is the bearing.

dc brushless motor: a nice spindle for CNC machine

dc brushless motor is common in reinforced concrete vehicles. They are small in size, light in weight, fast in speed and cheap in price. Raynerd wants to buy a new spindle for his CNC machine, and he thinks the dc brushless motor is a good platform.
At first, there was a motor with a 8 millimeter shaft on the shelf. The size of this shaft is important because the dc brushless motor shaft will be replaced by an ER16 pinch shaft of the same size. A chuck is a device for fixing tools, which is used to fasten cutting tools by folding rings around the cutter. The fixture allows quick replacement of the tool while providing a powerful clamping force. ER16 is one of many collet standards.
The main shell is made of aluminum specially for this project. The housing accommodates two radial load ball bearings to support the new rotary chuck. There is another bearing in this assembly, this time a thrust washer that prevents the axle rack from moving axially in the housing.
The standard ATX power output of 12 volt voltage is used in the test system. The electronic speed control and Servo Tester for general reinforced concrete vehicles work together to manually adjust the speed of the spindle. Therefore, the dc brushless motor is definitely a good platform to build from.

bldc motor: more efficient than brushed dc motor

bldc motor needs more complex control design and drive circuit. In place of the bldc motor single door driver and power field effect transistor, each phase of the bldc motor needs to take out 6 memory, each memory is composed of three half bridge pairs.

The designers of power tools are constantly taking on the task of cramming more electronics into the same or smaller space. The first is to switch off the wires by switching to battery powered equipment. Due to the need to save battery power, there are more complex control schemes, sensors and power drive devices, from brush DC motor to a more efficient bldc motor.

Wireless and BLDC blocks require very different feature sets. Control bldc motor calls high resolution pulse width modulation (PWM) timer, multi-channel analog-to-digital converter (ADC) with necessary conversion speed, general input/output (GPIOs) interrupt capability, and wired connection options. Wireless MCU needs to have RF front-end, high-frequency reference clock, digital phase-locked loop (PLL) and DSP modem and other functions.

Dividing wireless and BLDC functions into separate MCUs is a tested option, but it’s better to combine the two blocks into a single MCU. It creates a more compact solution while reducing power consumption and BOM costs. Of course, the selected microchip must contain the required peripheral blocks, processing power, and memory required to perform bldc motor and wireless functions.

nema 17 stepper motor: easy to install in AD88 3D printer

Nema 17 stepper motor is used in my own first 3D printer.
The AD88 3D printer is in the prototype designed by me in the tinkercad modeling program from 0.
Why did I do that?
I’ve always drowned a 3D printer, but we all know how hard we find them and at what prices.
7 months ago my brother bought such a printer after 4 months of intensive work. He recently had a problem with him and was forced to buy the piece at a printer (extruder). This is where I came up with the idea of building my own 3D printer.
I’m interested in the internet but I have not found an easy-to-use printer model with the materials I have at my disposal, so I decided to design my own printer.
After many hours in front of the calculator I managed to create prototype AD88 with nema 17 stepper motor.
Right now I do not know if this prototype will work just like a printer but I hope my measurements and my imagination have helped me.
Now that I learned where the idea of this project came from, let me tell you how she got this name. This printer, without realizing it, was designed on 08/08/2018. So I decided that her name would contain 8, and AD comes from my brother’s initials who helped me with my parts and my homework.
For this project we needed:
-4 nema 17 stepper motors from STEPPERONLINE
– about 1 kg of filament.
– threaded bar with thickness of 8mm and 3m.
– fine bar 8mm thick and 1m long.
– 12 linear rollers
– Two pulleys
– 2m GT2 toothed belt
– Extruder
– the drivers
– Three buttons
– and other improvised material.
– 2 threaded rods
– 50 nuts 8mm
Once all the materials have come, I will come back with the novelty and programming code, respectively the program.
If there are some improvements to this prototype, it can have a much larger print distance, much better precision and stability. This is version 1.0. And now I understand that it is not so easy to project anything from 0, especially if you have no idea what design means.
After I temporarily mounted the frame I notice that it has small design faults, in the sense that some parts should have been larger and others could have been smaller.
Finally, I will be happy if my prototype with nema 17 stepper motor will be able to print at least simplistic things.

nema 17: used in a plotting robot

Nema 17 is used to Build a free-standing, autonomous robot capable of creating an accurate plot from a set of Cartesian coordinates.
Pen plotters work by precisely moving either the plotting head or the plot medium or both. The size of plot that can be created is limited to the platen size of the printer. This project mounts the print head on an autonomous robot capable of precise movements in two orthogonal directs: x and y. Because it is freestanding, plots can be drawn directly onto floors, sidewalks, and other smooth concrete surfaces. The basic design can be scaled up for a machine capable of plotting on roads, runways, etc.
Finding a pre-made, small, rugged, adaptable chassis for the project proved difficult. Selection was further complicated because the print head needed to be centrally positioned and be able to access the print surface, The VEX Robotics 15×16 Chassis Kit (Small) was usable but not perfect (Figure 1). The primary problem with this chassis is that the spacing of mounting and connecting holes are based on Imperial units and many of the connected components use metric spacing. Mount holes had to be drilled or extended, weakening the chassis. The best but expensive solution was to have a custom chassis fabricated.







Figure 1. Plotting robot built on the small chassis kit from Vex Robotics to which Mecanum wheels are mounted to roll in parallel but the roller axes are perpendicular to the two adjacent wheels.
Omni versus Mecanum Wheels
There are two different types of wheels used for moving vehicles in two orthogonal direction: omni wheels (Figure 2) which can roll in one direction and be pushed on their rollers in the orthogonal direction (available from RobotShop), and mecanum wheels (Figure 3) that, when mounted in sets of four, can be powered to roll in one direction and, when the front and back wheels are rotated in opposite, directions, will move in the orthogonal direction (also available from RobotShop).





Figure 2. Omni wheels rotate in one direction and the rollers move in the orthogonal direction.






Figure 3. Mecanum wheels rotate in one direction but when mounted in pairs and rotated in opposite directions, moves the wheels in the orthogonal direction

To enable movement in two orthogonal directions, omni wheels may be mounted in two sets perpendicular to each other to roll in orthogonal directions (Figure 4). When using mecanum wheels, all four wheels roll in the same direction but the roller direction is perpendicular to the direction of the rollers across and in line with it. To move obliquely, the robot moves a minute distance in the x and then in the y directions (Figure 1). Nema 17 is uniquely able to make the precise, minute movements necessary. Many of the STEPPERONLINE nema 17motors have ¼” D-shafts ideally suited for the attachment of either wheel type using hubs with 8mm diameter mounting holes (Figure 5). Mounting brackets available from STEPPERONLINE are ideal for mounting the stepper motors because the motors are held precisely and tightly and the mounts are very strong and inflexible.






Figure 4. Omni wheels are mounted in two sets to roll in two orthogonal directions.







Figure 5. These hubs, available from RobotShop, can be attached to either omni or mecanum wheels and mounted on the ¼” D-shaft of stepper motors.

Microprocessor control
A variety of microprocessors can be used to move the wheels. Both Arduinos and Raspberry Pis have been used successfully. Although the wheels can be turned simultaneously using parallel processing or multiple microprocessors, it was easier to move each wheel successively a minute amount. Because space on the robot was limited, it was not practical to use the digital stepper drivers available from STEPPERONLINE . Drivers based on the L298 H-bridge driver were tried initially (Figure 6). Because these can only drive whole and half steps, stepper motors with a 0.9° step size were used to achieve the resolution necessary. Because of its limitation to half steps and because all wheels must be moved as close to simultaneously as possible and the L298 is relatively slow, faster and more sophisticated drivers from Allegro MicroSystems and Texas Instruments (TI) were tested. The TI DRV8825 was found to work best (Figure 7). The DRV8825 on a board from Pololu was mounted so that the step size the step size could be changed by the microprocessor.







Figure 6. L298 H bridge




Figure 7. The TI DRV8825 is fast, provides a up to a 1/32 step size, can easily handle currents up to 1 amp and above






Figure 8. To keep the weight over the wheels roughly equal, the robot is powered by two lead-acid batteries wired in parallel.

Yaw correction
The system worked well but, with larger plots, the robot rotated about its vertical axis (aka yawed) about its vertical axis. A Bosche BNO055 absolute gyroscope was used to measure and correct for this rotation. Because the BNO055 requires clock stretching and the Broadcom BCM2836 microprocessor used in the Raspberry Pi has problems handling this, the BNO055 was run by Arduino Nano which was read via serial by the Raspberry Pi over the USB connection (Figure 9).




Figure 9. Rotation of the robot about its vertical axis was measured by a Bosche BNO055 absolute gyroscope run by an Arduino Nano connected to a Raspberry Pi.

Initially, to reduce weight, a NiMH battery was used for power. This arrangement worked but not well. A design using 12V lead-acid storage batteries was used instead. Because the battery is quite heavy, to keep the weight over each wheel roughly equal, two batteries were used wired in parallel. Because the robot weighed in excess of 53 Newtons, nema 17 geared steppers motors from STEPPERONLINE were used.

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