Naked truth about stepstick modules with A4988 chip from Allegro MicroSystems.

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Naked truth about stepstick modules with A4988 chip from Allegro MicroSystems.

Post by _kaktus_ » Sat Jul 13, 2019 11:49 pm


You can meet legends that green modules are better than red ones (or vice versa - maybe I knocked).

Is it true and what is the origin of this myth :?:

One thing's for sure. The colour of the module is due to the soldermask used. The driver's chip is always the same. But ... There are minor differences in the hardware design.

The color is supposed to distinguish a particular type of equipment. We owe it to the marketing catwalk.
However, I have seen the modules or their photographs published on the Internet where this dependency was not consistent. :D

We will now look at what it's all about in order not to get crazy and avoid a few mistakes.

The design of the electronic system enables the nominal current to be adjusted to the type of stepper motor used.

This makes the construction more universal.
However, the value of the maximum current that can supply the module to the motor becomes very limited.
The chip manufacturer informs you that the continuous maximum current of the driver is :
The A4988 is a complete microstepping motor driver with built-in translator for easy operation. It is designed to operate bipolar stepper motors in full-, half-, quarter-, eighth-, and sixteenth-step modes, with an output drive capacity of up to 35 V and ±2 A. The A4988 includes a fixed off-time current regulator which has the ability to operate in slow or mixed decay modes.
I haven't seen the module using this chip that would allow to achieve these parameters. :lol:

Well, I lied ... except for the new design of the Polulu brand. But I'll tell you about it later.

the picture below presents the modules that can be purchased in popular trading platforms:
moduly_A4988.png (4.68 MiB) Viewed 12010 times
At first glance, the modules only differ in the colour of the soldermask, but is that the last difference?
A seasoned observer will notice the details that make these constructions unique.
And it is these details that give the individual features of each of the presented modules.
Of course, by limiting the functionality of the driver's chip. :lol:
moduly_A4988-3.png (4.84 MiB) Viewed 12010 times

The modules are distinguished by resistors in the motor circuit and the operating mode control circuit.
From now on, with new knowledge, everyone can individually influence the performance of the module and change the driver's operating mode.

Of course, let the data sheet A4988 be a obligatory reading.

I have already presented the module circuit diagram on another occasion.

However, it must be said that it concerns the new version of the Polulu module, contains better customized resistors in the motor circuit (Rsense), and has a slightly differently constructed reference voltage circuit (Vref) for output current regulation. :D

To correctly calculate the Vref setting for the current to be supplied, read the value of the Rsense resistors and use it in the calculations.
To achieve this, you should also know the operating parameters of the stepper motor.
The regulation can also be done experimentally, but it is important to note that motors or driver chips can easily reach dangerous temperatures.

The whole process is described in detail here, so I will not repeat it.

Kat, thank you for the reviews and your opinion.
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Re: Naked truth about stepstick modules with A4988 chip from Allegro MicroSystems.

Post by William » Mon Jul 15, 2019 9:33 am

Thanks for your share. :D
-Keep your mind and try to test it. :)
-Everything will be fun!-Support all Getech printer.
-You can ask me the questions and I will kindly reply.
-Respect others is the best way you can get help!

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