Cost Saving Encoder Installation For Miniature Dc Servomotors
29 November 2007
Rotalink has introduced a single-channel encoder, which allows standard, single-shaft dc motors to be adapted for closed loop position feedback applications. The ruggedly constructed 24-pulse/revolution encoder offers cost savings for both volume and smaller quantity applications.
For miniature DC motor/gearbox applications where position or velocity feedback is required, it is almost always necessary to specify a double-shaft motor and fit a 'kit' encoder on the rear shaft. This often necessitates having to accept a non-standard motor with implications of higher cost and extended delivery.
Rotalink's designers have applied lateral thinking to this challenging problem and developed the new encoder with minimal height to allow mounting between the front end of a single shaft motor and the chosen gearbox providing both the encoder function as well as the motor-gearbox adaptor plate. This modular approach allows the encoder to be used with a wide variety of motors in combination with almost all the precision spur and planetary gearboxes available from Rotalink's standard and customised range and means that customers benefit by specifying off the shelf components reducing development costs, product costs and timescales.
The single channel, 24 pulse/revolution encoder uses a magneto-resistive sensor and magnetised disc and provides a DC square wave output voltage that is the same level as the input voltage. Any voltage between 3.8V and 30 VDC can be used enabling TTL (5V), or CMOS (12V or 15V) voltage levels in the motion control system. As the encoder pulses seen at the control system are multiplied by the gearbox ratio, the angular positioning resolution at the gearbox output shaft, or the linear positioning resolution if a leadscrew is used, will be more than sufficient for high resolution, closed loop servo applications. The encoder can operate at speeds well within the maximum gearbox input speeds so performance is guaranteed.
DC servo motor/gearboxes with closed loop control offer designers many performance benefits over open loop positioning systems such as stepper motors by providing smoother performance with improved speed regulation and tighter position control as well as higher efficiency, higher power density, lower power consumption and minimal audible noise.
The new encoder will attract interest in many applications where closed loop servo performance is required such as medical and analytical instruments, office automation, vending machines and dispensing equipment.
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