29-03-2010, 10:47 PM
(29-03-2010, 08:22 PM)Archie Wrote: Could you be so kind to just go over the timer relay (WJR) within the circuit, 7.5 seconds I believe and it's main function, is it to do with in case of an obstruction, and and detection cannot be achieved in this time.
Without going into detail of how it works, its purpose is to cut off the motor after a time if the detection is not made up, mainly to stop the motor burning out as would happen if it continued to run until the techs arrive. There is normally some sort of clutch that slips or hydraulic bypass to deal with the time in between the points stopping moving on an obstruction and the motor cutting out.
Why 7.5 secs? Who knows!?!?!?