The idea behind the project is simple: take a stepper motor, put a needle on it, and connect it to a mbed. Instant analog gauge, measuring anything the mbed can calculate.

Description

These stepper motors are often used in gauges for motorcycles and cars to replace the old-style fully-analog type. They have extremely fine step precision of about 1/2 a degree per step, 600 steps for single stepping, fast response for quick movements, and a range of 315° degrees. Their smooth motion makes good for small projects that need a dial indicator, and more precision motion than you can get with a needle gauge.

This is a bi-polar stepper motor and you need to have some sort of H-Bridge to drive it. A L293D or TB6612 will do the job nicely. You can have a microcontroller that can drive 200 ohm loads; this way you will be able to use the direct pins without extra MOSFETs.

The motor is quite 'weak', not good for moving anything but a light indicator. We have a red-line dial that fits nicely on top by pushing onto the needle shaft.

Technical Details

• Axial Force Maximum: 150N
• Axial Pull Force Maximum: 100N
• Radial Force Maximum: 12N
• Rotation Angle Maximum: 315°
• Coil Resistance: 260 ohm
• General Tolerance: ± 0.1 / ± 5°
• Rotation Angle Maximum: 315°
• 600 steps per 'rotation' (315 degree rotation)

Dimensions:

• ​Red-Line Dial Diameter: 13mm / 0.5"
• Red-Line Dial Length: 42mm / 1.65"
• Dial Thickness: 1mm / 0.04"
• Motor Diameter: 32mm / 1.3"
• Motor Thickness (w/o pins): 9mm / 0.35"

Schematic

Video

The movement of the needle is amazingly smooth and quite fast, as seen in the video. This is really good if you want a more analog display than LEDs and LCDs can provide.

Source Code

#include "mbed.h"
#include "StepperMotor_X27168.h"

StepperMotor_X27168 smotor(p25, p26, p23, p22);

int main() {

    smotor.step_position(180);
    wait(0.5);
    
    smotor.step_position(100);
    wait(0.5);
    
    smotor.angle_position(270);
    wait(0.5);
    
    smotor.step_position(0);
    wait(0.5);
}