Pulse Generator Tells Your Motors “Get Ta Steppin”

Stepper Motor Pulse Generator

Stepper motors are great for a bunch of projects; CNC machines, clocks or robots for example. Sometimes when working on a project that does include a stepper motor and driver, it would be nice to test that part of the build without hooking everything up. A pulse generator could be used to complete such a task and [CuteMinds] has put together a DIY friendly version tailored specifically for stepper motors. This device makes quick and easy work for testing out those stepper motors.

At the heart of the pulse generator is a 12F675 microchip which looks to the resistance value of a potentiometer to adjust the square wave step signal output from 20hz to 3khz. Just having the step signal would pretty cool but this project goes a little farther. There are 3 sets of headers on the board that allow you to connect either a jumper or switch in order to: 1) turn the power on, 2) enable the stepper driver and 3) select the direction the motor turns. The on-board batteries make this unit portable for remote usage.

If you are itching to make one for yourself, the Eagle schematic and board files are available for download at the above link.

Building a stepper driver

[TBJ] is building what he calls a junkbox 3D printer. You can probably guess that he’s trying to salvage most of the parts for the device, and after pulling a stepper motor from an old printer he was in need of a way to control it. What he came up with is a stepper driver that uses discrete components that are easy to acquire and inexpensive. The design calls for two inputs, one that toggles the direction in which the motor will spin, and the other that triggers one step of the motor. A CD4013 dual flip-flop takes care of both of these inputs in one chip package.

The motor is driven by a pair of H-bridges that he built using six transistors each. The trick with a stepper motor is that you need to drive the four poles of the motor to a specific logic level at a specific time. For this [TBJ] uses a CD4017 decade counter. A network of diodes grounds half of the output lines based on the flip-flop that controls direction. Our friend the 555 timer provides a clock for the circuit, keeping everything moving at a predefined rate. Check out the video after the break for an explanation and demonstration.

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