Tuesday, November 11, 2008

Mardus-Kreutz Unipolar Micro-stepper Drive.



Introduction

The Mardus-Kreutz unipolar micro-stepper board was born from a thread in CNCzone.

One of the members, Mardus, asked why DIY discrete unipolar micro-stepper drives were not available. Some of the participants tried to find a logical explanation and a challenge was created to provide a working DIY unipolar micro-stepper.

A few weeks later the first prototype Mardus-Kreutz board was designed and successfully tested. This blog will try to provide information about the design as well as step by step instructions of how to build a working, high quality, unipolar micro-stepper drive.


Mardus-Kreutz board specifications:


Maximum motor voltage: 80Volts
Maximum current: 8 Amps (peak) per phase
Current regulation type: fixed frequency chopper at 39.2 Khz
Micro-step modes: Full, Half, 1/4, 1/8, 1/16, 1/5, 1/10.
Standby current reduction (to 50%) after 1 second inactivity.
Automatic torque compensation and Current waveform morphing on all micro-step modes.
Command interface: Step-Direction (opto-isolated inputs), Motor Enable.
Minimum Step/Dir Pulse width: 2 microSeconds
Auxiliary power supply: 12 - 15 volts DC, non regulated.
Minimum motor current: 1.5 Amp r.m.s. per phase
Stepper motor types: Unipolar, 6 and 8 wires.
The design uses low cost components.
Modular approach: Translator and Power stage (two separated boards).
PCB Assembly complexity: Low/Medium (most components are trough-hole, uses only a couple of SMD components). The translator boards could be made on perforated prototype boards.



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