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28BYJ-48 (5V power) stepper motor with gearbox

This is a stepper motor widely used in various hobby constructions, and you can use it with SimVimCockpit too for some instruments. It's an unipolar motor but it can be easily converted into bipolar to work with controllers that drive bipolar stepper motors.

Speed

Note that this motor can be used for those gauges/mechanisms that take about 4-5 seconds to rotate 360 degrees. This motor requires a minimum lapse between steps of about 1.8 milliseconds (without load). In SimVim firmware it is set to 2.4 ms to guarantee stable work. This time is needed to prevent the motor from getting stuck when momentary data value changes too fast, causing the stepper to skip several steps, desync and stop moving.

In full step mode 360 degree rotation for this stepper takes 2048 steps, that gives you 5 seconds per rotation (12 rpm ) at the maximum speed. This is quite enough for many aviation instruments. And don't worry if some data will momentary change rapidly sometimes - the stepper firmware will not loose steps and all you can notice in this case is that the gauge needle may have some lag in movement.

Convert to bipolar


Voltage

The motor is rated at 5V and you should not overpower it. You need to power it (using the M+ input) by an exact +5V supply, no more! Not because it can be burnt, but because if using this motor with the A3967 controller and voltage of 6+ volts the stepper will skip steps and loose precision.

To work in SimVimCockpit you should drive this stepper in full steps mode (the fastest mode and high torque). For this you need to set the controller you use to drive the 28BYJ-48 stepper motor in the "full-step" mode. For the EasyDriver board (or similar boards designed around the A3967 chip) you need to short both MS1 and MS2 step mode inputs to the GND.



To work in SimVimCockpit you should drive this stepper in full-step mode (the fastest mode and high torque). For this you need to set the controller you use to drive the 28BYJ-48 stepper motor in the "full-step" mode. For the EasyDriver board (or similar boards designed around the A3967 chip) you need to short both MS1 and MS2 step mode inputs to the GND.


Start Position Sensor

To synchronize your gauge with the simulator, using a start-position sensor for 28BYJ-28 motor is required. As this motor has high-ratio gear, and thus, high torque, you cannot use a mechanical stopper as a limiter ( if the needle is firmly fastened on the shaft *). Only some end-switch or optical IR sensor can be used.

(*) Actually, you can use a mechanical limiter too, if you fix the needle on the motor shaft firmly enough for normal work, but loose enough to rotate (slip) on the shaft when it is stopped by the limiter.

The end-stop switch can be used for sectoral gauges, and IR sensor - for both full-circle and sectoral instruments.

Note: When you have no sensor (or no working sensor), on reload the stepper will rotate CCW by 360 degrees, after that it goes to the position defined by the current value. Of course, it will be in different positions after each reload, due to lacking a working sensor.




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