Stepping motors are widely used in automation due to their high resolution, precision positioning, minimal control electronics, and low cost. As an open loop system, traditional step motors are driven without the need for sensors to feed information back to a controller; however, the open loop configuration of step motors has challenges.
Stepper motor encoders provide speed and positioning feedback. In today’s wide range of applications in medical, industrial automation and security, encoders are a vital component for tracking motion in a closed-loop system.
Portescap offers three technologies for feedback and positioning:
Optical Encoders
The stepper motor optical encoders offer two-channel quadrature output and and an index pulse. The encoder uses a dedicated ASIC having a matrix of optoelectronic sensors which receive infrared light from an LED after its passage through a metal codewheel. The mask determining the phase angle and index position is directly integrated into the circuit. The light/dark signals are converted into electrical pulses for channel A and B.
Magnetic Encoders
Portescap magnetic Type D and F encoders incorporate a multipolar magnet that is directly mounted on the motor shaft. As the motor shaft turns, magnetic flux variations are detected by hall sensors, which generate two TTL-CMOS-compatible output signals having a 90° phase shift between channel A and B.
Magnetoresistance Encoders
The MR2 encoder uses a bipolar magnet. An MR angle sensor measures SIN/COS magnetic field measurements. An interpolator converts the SIN/COS signals into two square wave output signals (channels A and B).
An established technology, optical encoders offer accurate and reliable performance along with a wide range of resolutions; however, they are susceptible to signal degradation and loss when exposed to dust, oil, or similar contaminants. They are best used in clean environments. Capacitive encoders utilize newer technology, offer similar benefits, and ultimately provide the same position and speed information as optical encoders. But they are immune to environmental contaminants.
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