MAGNETIC FIELD AND FORCE CHARACTERISTICS OF A SOLENOID ACTUATOR FOR DISPLAY BOARD APPLICATION

The work described concerns a technical assessment of a small linear actuator that was developed for use in large, electronically controlled, electromechanical display boards. Each pixel of the board is driven by an individual actuator and displays alternative colours to the viewer, according to the position occupied by its armature. In operation, the whole screen can be refreshed a few times per second, and an actuator life of about 100M operations is required. No coil excitation must be needed when the armature is stationary, to minimise heating. Detent positions are therefore essential and these are achieved with the aid of a permanent magnet.