How microstepping drivers work

Microstepping drivers work on the principle of crushing motor steps, which allows them to control the motor with greater precision and smoothness. Instead of moving a full step, the motor can take small “micro-steps”, which reduces vibration and increases the resolution of the system.

Advantages of microstepping drivers

The main advantages of microstepping drivers include:

• Smoother motion and reduced vibration;
• Improved positioning accuracy;
• Improved positioning system resolution;
• Reduced motor operation noise.

Selecting a microstep driver

When selecting a microstepping driver, several key characteristics should be considered:

• Current and voltage: the driver must match the required motor parameters;
• Microstep resolution: determines the number of possible microsteps per full motor step;
• Type of control interface: stepper and guide signals, interface with microcontroller, etc.

Tuning and optimization

After selecting the right microstepping driver, it is important to properly configure it for your system. This includes setting the correct winding current, setting the microstepping current, and selecting the optimal control parameters.

Applications in various fields

Microstepping drivers are widely used in a variety of applications including 3D printing, CNC machining, medical devices, and factory automation. Their advantages make them an indispensable component for precise and smooth motion.

Microstepping drivers are an important link in drive control systems, providing high precision and smooth motion. Understanding their operation, selection and configuration will help ensure optimal performance of your system.

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Enclosure drivers like DM422, DM542, DM556, DM860, TMC2160 and so on, there are many such models.

Enclosure drivers like DM422.jpg Enclosure drivers likeDM422.jpg
The main difference, as it is easy to guess, is the enclosure design, which gives a number of advantages, such as a large cooling area, convenient I/O, control connectors and clear switch setup. They are designed for high currents and long, highly loaded operating modes. Often used on “large”, rather powerful CNCs, such as lathes, milling machines, manipulators, factory automation systems and other similar machines.

Most of the settings are made by a combination of jumpers, according to the table on the case, other models are additionally “fine-tuned” via RS232, UART interfaces, etc., which allows them to be used in a wide range of applications. Depending on the complexity and price, they are equipped with additional functions such as resonance compensation, winding short circuit protection, reverse EMF, stepper motor rotor holding mode and so on.

The price of different models varies greatly – from one and a half thousand to tens of thousands of rubles, when choosing should necessarily take into account how powerful you need a driver for your task and what additional features and functions it necessarily needs.

Enclosure drivers are definitely the best choice if size and price do not matter, most 3D printers can not afford such an under-the-hood space, so they create specialized compact devices for them.

A4988. Perhaps the cheapest, but also one of the most reliable versions of the printer driver. Motor current up to 2 A is regulated by a trim resistor, the mode of step splitting from 1 to 1/16 by jumpers. There is protection against short circuit, overvoltage, overload and overheating. An aluminum heatsink is included. That is, the driver is a kind of analog of a Kalashnikov machine gun – simple, reliable, cheap. There is a disadvantage – very noisy, if the printer is at your home, forget about sleep, rest and mental labor in its presence. For a printer placed in a garage, workshop or production, the choice is excellent.

DRV8825. Of the positive differences from the A4988 – finer pitch crush mode, up to 1/32, slightly more powerful, up to 2.2A. Otherwise it is worse, and seriously so. It works extremely loudly, sometimes unstable, at high speeds and loads often skips steps, and it is twice as expensive as the previous one. It is not recommended for purchase, much less for use.

LV8729. Quite a successful driver model. Pitch splitting up to 1/128, quiet operation and high stability. Excellent for NEMA 17 stepper motors. The only disadvantage is relatively low power, up to 1.5 A, but for most household printers this is more than enough, especially when it comes to controlling the Z-axis or filament feed. The price is comparable to DRV8825, with incomparably higher quality.

ST820. Powerful giant according to the manufacturer’s statement – up to 6.8 A of current to the windings, however, in reality it draws no more than 1.5 A. Why was it necessary to praise it so much is unclear. According to the same claims, it crushes a step into 256 microsteps, but even this is questionable. In general, the driver is average in everything, both in capabilities and characteristics, noise and price. The Enable channel is inverted for some reason. It can’t boast of one hundred percent stability, some modes are difficult to operate. The price is average. In general, we do not recommend it.

S6128 (SD6128). Microstep up to 1/128, current up to 2.2 A, not quiet, but it doesn’t howl at the whole apartment like DRV8825. The price is average. Does not stand out in anything, neither for better nor for worse. In general, quite a working option for office or educational printer.

TMC2100, TMC2130, TMC2208. A series of similar drivers with slight differences in features. These are probably the most advanced drivers for 3D printer at the moment. The standard step is divided into 16, but by command via UART or SPI you can split it up to 256 parts. The splitting is done using the proprietary stealthChop technology, which allows the drivers to operate extremely smoothly and quietly. Supported current up to 2A for the TMC2208 and up to 2.5A for the others, which is not bad. Dynamically varying the current depending on the load keeps the chip from overheating unnecessarily, while still providing high torque and hold. Despite the slightly higher price, highly recommended to buy and use if you value silence, quality and reliability.

There are several more models, both outdated and exotic, but we will not dwell on them, as we have already decided on the best option – TMC2208.

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The magnet engagement can be controlled directly by microcontroller commands. Low-voltage stepper motors work directly from pins or by means of shift registers, for high-power and high-voltage stepper motors you will need to build a rather complex power H-bridge for two coils and open signals in pairs of those or transistors.

That’s all well and good, but this approach has a few drawbacks. You need an H-bridge with precisely calculated parameters, TTL transistors, induction protection, and other engineering solutions. You need a minimum of four pins to control one motor, if the motor is bipolar on two windings. 3D printers are known to have a minimum of 4 stepper motors, which means finding 16 free pins can be a problem. From the first comes the second disadvantage – increased load on the computational resource, which is already fully utilized on printers.

It would be possible to tell the motor when and at what moment to make a step. This possibility is provided by the hero of our article – stepper motor driver.

A stepper motor driver is an electronic device that controls the motor windings, guided by commands from a microcontroller. A driver can be designed in different ways, but any driver has a few mandatory elements. Input: two signals, DIR – direction and PUL – command to execute a step, output: two contacts on one coil, called “A”, and two on the second – “B”. What happens inside the driver is a great mystery covered by the developers, but at the output we get what we need – power pulses to the motor windings.

Otherwise, different drivers may have differences, and serious ones, for example, in terms of allowable voltages and current strength. The simplest versions of drivers have no settings and work according to a minimal algorithm, like the one shown in the first picture: the windings are switched on, alternately reversing polarities. In this case, the rotation is jerky, noisy, but most importantly, it does not provide maximum torque.

For more powerful and smooth rotation, the motor works in so-called “half-steps”. Intermediate positions appear between the main positions, when both windings are switched on simultaneously in the correct order.

More complex variants are also possible, in which different voltage levels are applied to the winding pairs, thus dividing the half-step into several gradations. The oscillogram of “multistep” operation is much more complex and represents four broken step lines in a bizarre way. Signal algorithms vary from manufacturer to manufacturer, there are more successful ones, and there are smaller ones. But one thing is certain, the more gradations of pitch, called “microsteps”, the smoother and quieter the motor runs. Providing the motor with half steps and microsteps is also the driver’s task, the controller doesn’t need to keep track of it. Taking into account that there can be up to 256 such gradations for each step, we can conclude that drivers make the controller’s work tens and hundreds of times easier, while providing smooth and continuous motor control.

Some drivers are capable of additional tricks, for example, regulation of current power depending on the load on the rotor, which saves energy and reduces heating of the driver and motor, as well as other useful and not so useful things.

Some drivers initially strictly adhere to one single algorithm of operation, while others are able to change parameters: power, number of half-steps and other settings by program commands or hardware switches.

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