One of the members, Mardus, asked why DIY discrete unipolar micro-stepper drives were not available. We used Basic, as programming language, because the code was intended to be used as a learning tool, and well commented Basic code is simpler to digest. The dual Mosfet driver chips employed in our circuit have an external inhibit input one per individual Mosfet driver which is driven by the corresponding latch output. Desoldering pump Soldapult or equivalent with anti-static tip. Nothing that really were going to affect performance. The current control circuit is the heart of the Power stage.
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Posted by Kreutz at 5: Current Reference is individually adjustable by potentiometers and measured on individual test points for each coil. A few weeks later the first prototype Mardus-Kreutz board was designed and successfully tested.
marvus Posted by Kreutz at 7: The result of the comparison between the actual coil current and the reference voltage resets the S-R latch when the actual current produces a voltage on the sense resistor whose value exceeds the reference voltage. Our unipolar stepper drive’s current regulation circuit is based on a fixed frequency chopper with “blanking time”.
The Sync signal is generated on a hardware 8 bits PWM generator inside the Micro-controller Chip, the “blanking time” is adjustable in the firmware.
Mardus-Kreutz DIY Unipolar Micro-stepper Drive
Not available anymore, design has being sold. Originally Posted by ozan. For instance the one going to pin 4 of U2 was modified.
This component is a really critical component on our design. Stepper Motor theory is beyond the scope of this blog, there is a fine tutorial on the subject I would like the reader to familiarize with before continuing reading this blog. Most of the design goals become constrains on the development of the firmware: K-4 Bipolar Micro-stepper Design Goals.
Translator’s bottom side click to enlarge. Updated Step-Sequence information with some comments. Optional External Interface board could be added later for additional control, power and safety features.
Kreutz-4 DIY Bipolar Micro-Stepper Drive
The Speed measurement circuit is the responsible of controlling the variable morphing reference waveform versus motor speed, details about both features will be discussed on the firmware description part of this series. I’m very interested in build this Stepper driver.
We will be referring to some concepts explained on that tutorial on the description of the circuits on the following posts. The design includes an expansion port 20 pin IDC connector on ,ardus interface board, in order to provide access to the non used LPT port pins for functions like: Each channel’s chopper stage is basically integrated by a SET dominant S-R latcha dual Mosfet driver and a voltage comparator.
What I want to make clear is that there are many ways to get any stepper motor running, our design objectives were always focused into micro-stepping driving unipolar motors, but also to get the most of them, in terms of power, accuracy, efficiency and performance.
Translator and Power stage click to enlarge. The Unipolar Power Stage.
Mardus-Kreutz DIY Unipolar Micro-stepper Drive: Mardus-Kreutz Unipolar Micro-stepper Drive.
Nothing that really were going to affect performance. 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. The objective of the introduction of a “Blanking time” is to overcome the problem presented with switching transient currents as soon as a power Mosfet is Turned-ON.
K-4 Pc interface and M-K unipolar up to 80V – 8 Amps micro-step power stage’s schematics, gerber files and unipo,ar are unipolxr for free. The power stage receives Sync pulses from the translator as well as the following signals: Basically, the translator contains the brain and soul of the unipolaar drive. The reason of the splitting is simple, the reference signals are sent to the Power stage by means of a ribbon cable, noise captured on the cable is attenuated by the second low pass filter, located at the power board, before the analog signal amplitude is divided at the respective current setting potentiometer more detailed explanation on this subject will be offered later.
If an interrupt occurs during execution of a multi-cycle instruction, this instruction is completed before the interrupt is served.
Mardus-Kreutz DIY Unipolar Micro-stepper Drive: Mardus-Kreutz Unipolar Micro-Stepper. 2nd Part.
Both signals have to be processed in order to obtain two analog waveforms which will respectively become the Channel A and Channel B current reference waveforms. Charge Pump feature amrdus.
Thanks, Nasiri, for your help on this design. This nardus the response for some people’s complains about previous mosfet driver chip availability in other countries.