At least the power stage should be made on a double side PCB following the Rev2.1D or higher design. I provide the Gerber files for all the interested people who want to send them to a PCB fab, or want to etch or mill them by themselves. On the other side, there are a few people selling the bare boards or kits for both the M-K and the translators.
Another option is to use the K-4 four axis SMD PC Interface board (not a DIY board) to avoid ordering and assembling the individual translator boards and having to buy/assemble a B.O.B. (Break Out Box). The K-4 includes four translators and B.O.B. functionality.
Another option is to use the K-4 four axis SMD PC Interface board (not a DIY board) to avoid ordering and assembling the individual translator boards and having to buy/assemble a B.O.B. (Break Out Box). The K-4 includes four translators and B.O.B. functionality.
The K-4 PC Interface board has the following specifications:
- Operating Modes: Full Step, 1/2, 1/4, 1/8, 1/16, 1/10, 1/5.
- Opto-isolated Inputs and Outputs (except External Output interface signals). RF isolated Step-direction signals up to 2500 volts.
- +3.3 Volt or+ 5 Volt PC interface (jumper selectable).
- Automatic torque compensation.
- Automatic Reference waveform "morphing".
- Firmware Upgrade capability built in.
- External Output connector for interfacing the rest of the LPT port pins.
- Idle current reduction (50%) after 1 second inactivity independently for each axis.
- Charge-Pump (watch dog) circuit disables the outputs if the 12 KHz signal is not received from the software, protecting against Software "freezes" and LPT cable disconnections.
- A logic LOW at the EMG_STOP pin will disable all Axes and trigger a software E-Stop by pulling pin 10 of the Lpt port LOW.
- A Fault signal received from any of the Axes will trigger an Emergency Stop.
Individual Axis Specifications:
- Maximum Step rate: 100 Khz
- Minimum Step and Direction pulse width = 2 uSec @ 100 Khz.
- Step and direction signals are Active "High" (Low to High Transition).
- 40 Khz chopper frequency.
Bare PCBs Rev 2.1d
Some photos taken during prototype assembly:
4 comments:
Kreutz,
next to the education purpose, can you reiterate what are reasons/advantages to build a unipolar design versus a bipolar design ?
ed
A unipolar stepper motor has two windings per phase. Switching alternately each of those windings a magnetic pole can be reversed without switching the direction of current, so the commutation circuit can be a lot simpler. That has been the main attractive of the unipolar motors and drives so far, they are cheaper because of the driving simplicity.
Unipolar Drives have 50% less coil utilization that the equivalent bipolar drive (because only one winding per phase could be energized at a time), and so the maximum current per phase is limited by the coil resistance and heat-sinking capacity of the motor assembly (independently of magnetic saturation effects).
Torque is directly proportional to coil current, so theoretically maximum torque is also limited versus the equivalent (parallel connected) bipolar motor.
What is different on the Mardus-Kreutz design that allows us to increase the torque of the unipolar motor to be comparable to the bipolar motor's torque?
The maximum phase current in both, unipolar and bipolar motors is generally listed as r.m.s. current for Full Step operation. Full step current is a D.C. current level, so peak and r.m.s. values are the same.
On the Mardus-Kreutz drives, the firmware allows to use a current setting equal to 1.41 times the specified maximum current (corresponding to the peak current value for a sinusoidally driven motor with the same r.m.s. value), from then on, the firmware automatically compensates the torque (current) so to keep the r.m.s. current value constant independent of the mode and current waveform, so at Full step the DC level will be limited to the manufacturer's specified value, while at different micro-step modes it will automatically be compensated to get maximum torque by using a peak current above the full step DC value.
In order to avoid the overheating associated with stopping on a micro-step mode at a current value above the maximum DC level, a 50% current reduction is effected as soon as the drive detects 1 second inactivity of the motor.
The current level returns to the right value with the next micro-step, so position is never lost because the current, at both active windings, is proportionally reduced.
Because of that "trick" a unipolar motor, at least theoretically, will have approximately the same torque than a bipolar motor not using the same compensation technique.
There is no problem with magnetic saturation because we are still driving the motor within the manufacturer's r.m.s. limits.
Hola.
Me interesa tu controladora y quisiera construir una en mi casa para hacer un posicionador, pero estoy confundido con tanta versión del foro.
Como encuentro la última versión de cada placa y programa?
Puedes mandarme un enlace a mi mail:
a_s_e_g_a_d_e en gmail (sin los guiones bajos)
El código fuente también me interesa si está disponible.
Por lo que veo hiciste un gran trabajo.
Saludos y gracias desde ya :)
Hi.. I'm very interested in build this Stepper driver.. could you send to me luizlucasi at G_M_A_I_L
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