Uses of the Stepper-Motor in Amateur Electronics Projects and Existing Functions

The stepper-motor is used in hundreds of electronics applications – anything where a precise amount of motion needs to be controlled and
arrested. Floppy disk drives (where they still exist!) use the motor to control their lasers, as do CD players; printers; slot machines; and scanners.

Because of their stepped nature, stepper-motors are also used to position valves in fluid control systems (for example inside a combustion engine, controlling the amount of oil flowing round the system); and in medical technology, they are often used to maintain the precise position of lasers and lenses.

The stepper-motor is lauded for its robustness. Unlike a servo mechanism, which is expensive and delicate, a stepper-motor can be operated in a range of harsh environments, including ones where water or sand might be a problem for the more delicately controlled servo. The stepper, which is basically a gear cog surrounded by electromagnets, can operate regardless of difficult temperatures, the presence of saline in the air or other disturbing factors – the pull of the magnet is stronger and the mechanism by which the cog moves is simpler than its more fragile cousins.

One drawback of the stepper-motor: to get more precise accuracy, you need a much bigger cog. This is because each tooth in the cog represents one stage (“step”) in the motor’s rotation. So if you need to control very small increments of positioning with a stepper-motor you need a big cog, with enough tiny teeth on it to do everything you want.

Obviously at some point the electronics hobbyist has to make a trade-off between robustness and cheapness (the stepper-motor is inexpensive), and size. Where an extraordinary degree of precision is required, or where you wish to shut down the wobble effect the electromagnets have, you may have to go for the more expensive, less sturdy option of a servo mechanism,.

The stepper-motor suffers from wobbling motion at low torque. The electromagnets around the cog are switched on in sequence to make the wheel turn. A magnetic field is strongest at pint of origin and weakens as you move away from that point. At low torque the tooth of the cog is pulled past the strongest point of magnetism, and then flicks back to settle into it. This may present problems for some applications using the stepper-motor.

At high motor speeds, the torque slackens – so the motor becomes less stable the faster it goes.

The snapping motion of the cog tooth in the magnetic field is called a detent. The subsequent vibration means that the stepper-motor is noisier than some other forms of motor. You will hear this noise when you put a new CD into your CD player, or a DVD into the tray of your DVD player. That whirring sound is the stepper-motor snapping through its detents to get the laser eye positioned at the correct band on the disc.

n hobbyist electronics, the stepper-motor is frequently chosen for its strength, reliability and relatively low cost when compared to alternative positioning arrangements.

Author Bio:

Bryony Haines is a second year electronics student at Keele University. She is currently building a CD player using a stepper-motor.

This is a guest post by Bryony Haines about the uses of Stepper motor in Amateur Electronics Projects and their existing uses. To write guest posts for us, please follow the link below.

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