User Manual EA4709 / EA4718
ElectroCraft
®
E-Mail: [email protected] www.electrocraft.com May 2009
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Encoder
Is a feedback device which converts mechanical motion into electronic signals. The most
commonly used, rotary encoders, output digital pulses corresponding to incremental angular
motion. For example, a 1000-line encoder produces 1000 pulses every mechanical
revolution. The encoder consists of a glass or metal wheel with alternating transparent and
opaque stripes, detected by optical sensors to produce the digital outputs.
Back EMF
The voltage generated when a permanent magnet motor is rotated. This voltage is
proportional to motor speed and is present regardless of whether the motor winding(s) are
energized or de-energized.
Closed loop
This is broadly applied term, relating to any system in which the output is measured and
compared to the input. The output is then adjusted to reach the desired condition. In motion
control, the term typically describes a system utilizing a velocity and/or position transducer
to generate correction signals in relation to desired parameters.
Cogging
A term used to describe non-uniform angular velocity. Cogging appears as jerkiness,
especially at low speeds.
Continuous rated current
The maximum allowable continuous current a motor can handle without exceeding the
motor temperature limits
Continuous stall torque
Is the amount of torque at zero speed, which a motor can continuously deliver without
exceeding its thermal rating. To determined by applying DC current through two windings
with locked rotor, while monitoring temperature. It’s specified with motor windings at
maximum rated temperature and 25 °C ambient temperature, motor mounted to a heat sink.
Refer to individual specs for heat sink size.
Controller
This term describes a functional block containing an amplifier, power supplies, and possibly
position-control electronics for operating a servomotor or step motor.
