MullOverThing

Useful tips for everyday

# How do I know what position my stepper motor is?

## How do I know what position my stepper motor is?

To determine the shaft position of a stepper after power down, you have only two options. One is to use an absolute rotary shaft encoder, the other is to “home” the stepper upon power up, using a limit switch (and rotate back to original position).

## Do stepper motors slip?

The motors move and animate just like they are supposed to. However, it is when they move on the ground or when they carry load that they slip.

Does a stepper motor hold position?

This means that when the windings are energized but the rotor is stationary, the motor can hold the load in place. But a stepper motor can also hold a load in place when there is no current applied to the windings (for example, in a power-off condition). This is commonly known as the detent torque or residual torque.

How do you read a stepper motor?

Stepper motors are DC motors that move in discrete steps. They have multiple coils that are organized in groups called “phases”. By energizing each phase in sequence, the motor will rotate, one step at a time. With a computer controlled stepping you can achieve very precise positioning and/or speed control.

### What causes stepper motors to lose steps?

The reason is that the input of the motor power is insufficient and the torque generated cannot keep up with the rotor speed of the stator magnetic field, resulting the step loss. The rotor gains too much energy in the stepping process, resulting in the torque generated by the motor is too large and motor stepping.

### How to detect when a stepper motor has stalled?

To detect if your steppers have stalled check this questionhow to detect when a stepper motor has stalled. If you want to use absolute positioning you can create a linear potentiometer using a length of nichrome wire pulled across the axis, with the “wiper” touching where the bed/mill is moving.

Which is the correct starting position for a stepper motor?

If you want your stepper motor to have a 0-180º range of motion, set up a mechanic switch at the 0 or 180º point. During startup, move the stepper motor in the direction of your home switch until the switch is activated. Now you know the position of the motor, and can move it to the 90º starting position.

How can you tell if a motor is slipping?

What you might be able to do is to gradually reduce the holding current on one winding, and monitor the voltage on the other winding. If the motor slips as the holding torque is reduced, you’ll see one or more pulses on that other winding.

#### Can a micro switch stop a stepper motor?

Of course if you were to connect one of the drive wires directly through the micro switch you would need a switch rated to handle the full motor current. Also, completely opening one of the drive wires may cause the stepper motor to stall, though perhaps that would in itself be helpful in this case.