Encoder encompasses Hall sensor function 8-17-98

August 17, 1998 Design News

FEATURED PRODUCT

Encoder encompasses Hall sensor function

Geoff Nairn, Spain

A compact encoder series from Eltra s.r.l. simplifies control of brushless dc motors by combining incremental encoder and motor phase control in a single device. The EF encoder series optically generates the motor phase signals that in a traditional brushless DC motor are produced by Hall effect sensors mounted in the motor body.

In addition to the standard output signals of a conventional incremental encoder--resolutions from 200 to 2,048 lines per revolution are offered with or without zero index--the encoder disk of the EF series has three extra tracks to optically simulate signals traditionally generated by Hall-effect sensors. According to the phase angle between these tracks, the encoder can control DC motors with 4, 6 or 8 poles.

Eltra believes its new encoder offers several advantages over relatively expensive Hall-effect sensors located inside the motor case. The new encoder, for example, is typically located in a cooler, less hostile environment at the end of the motor shaft.

By eliminating Hall-effect sensors from the casing, design engineers can produce cheaper, more compact motors with simpler wiring. This, in turn, helps reduce electromagnetic interference.

Compatible with leading commercial digital drives, the encoder can be mounted on motors with shaft-hole diameters of 8, 10, 14 or 15mm. Hall Effect phase outputs can be configured as NPN open collector or line driver outputs. Power supply options are 5V or 8-24V.

Additional information, contact: Andrea Pedron, Eltra s.r.l., Via Monticello di Fara 32 bis, 36040 Sarego (VI), Italy. Tel: +39 0444 436489; Fax +39 0444 835335.