A StepStick Module for External Stepper Motor DriversDesigned by Bart Dring in United States of America
What is it? This is a StepStick (or Pololu) style module designed to control large, externally mounted stepper motor drivers. The StepStick style stepper motor drivers are used in countless design...Read More…
This is a StepStick (or Pololu) style module designed to control large, externally mounted stepper motor drivers.
The StepStick style stepper motor drivers are used in countless designs, but sometimes they don't have as much power as you need. Stand alone stepper motor drivers can be found that drive huge motors with lots of current.
These driver generally have opto isolators on the inputs. This isolates the noise and power spikes that could damage your controller. These opto isolators generally run on 5V and can pull a little current. Many microcontrollers can handle that current, but 3.3V microcontrollers can't deliver the specified voltage. Also, most CNC controllers use a common enable signal. It could damage your microcontroller if that one signal is connected to multiple drivers. The driver inputs typically look like this with + and - terminals for each signal.
This modules solves those problems. It uses a 74ACT245 buffer to drive the opto isolators. Each signal has its own 5V signal including the enable signal. The 5V comes from your motor power voltage (9-24VDC). Each module has its own power regulator.
The module is compatible with all StepStick style sockets including those designed for Trinamic SPI drivers, assuming there are step, direction and enable signals going to the modules. It directs the step, direction and enable signals through your existing motor connectors. If you controller actively controls step, direction and enable, this should work.
Input Motor Voltage Range: This module is designed to be run in a 9-24VDC range on the VMot pin. This is the voltage that would normally be sent the the stepper motors. The limiting factor is the 5V regulator. It generates heat proportional to the voltage. I ran it at 24V with all channels forced on (an unlikely mode) for over an hour and the part only got a little warm (no heatsink or fan). It was well below the rated temperature. The part is rated for 35V. If you can keep it cool, you get go a little higher. I chose the biggest regulator I could fit (T.I. LM78L05ACMX/NOPB)
Open Source: The design is open source. The files are located here.
Small scale CNC firmwares, like Grbl_ESP32 and Marlin are getting so good, that people want to use them on bigger machines. This modules helps you have success with those projects.
There are other, similar modules, out there that do not have any active circuitry and just reroute the signal to a connector. This may not work and does not provide a buffer to protect your sensitive and expensive microcontroller.
First solder on the header connectors. Solder them so the pins extend from the non-component side of the PCB.
Install the module into your controller. On the bottom of the module the corner pins are labeled. Match those labels to the labels on your controller.
The top of the board has some pins labeled with G (Gnd), En (Enable), Dr (Direction) and St (Step). Those pins go to 4 wires on your motor connector. You should use a meter to determine how the pins are connected. Each controller could be different. Also some controllers may not be consistent across all sockets, so check them all.
Wire your motor connector to your external driver. The circuit uses a common ground, so you need to connect all the grounds together at the motor driver.
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Tom | May 29, 2020
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