LiftMaster SW470 SW490 S3 BOARD Manual - Page 11

Preparing the Installation 11 ONE BUTTON CONTROL (SEQUENCE OF OPERATION) The one button control can be programmed to function as an open command unless on the open limit, where it becomes a close button. DIGITAL MICROPROCESSOR This is the main circuit board for the operator. It contains all the logic and intelligence for the system. All the system programming is done on this circuit board. See page 21. It is solid state and contains an emergency back-up system that works even if the processor is missing. INHERENT OBSTRUCTION PROTECTION The limit shaft is equipped with an R.P.M. sensor. When the gate meets an obstruction, the loss of r.p.m's will cause the gate to reverse. A second obstruction will cause the gate to stop and alarm. A renewed wired (supervised) input will restart the gate. EXTERNAL OBSTRUCTION CIRCUIT This circuit can be used with either a gate edge or a photo beam system. When either of the two devices mentioned are activated, the operator will react in a similar manner to the inherent obstruction described above. NOTE: If external entrapment protection is required by the class of operator, both an open and close protection device must be used. SPECIAL NOTE ABOUT OBSTRUCTION SENSING FROM EITHER INTERNAL OR EXTERNAL SYSTEMS The operator will stop if it senses two sequential obstructions. " If two (2) external obstructions occur, any control input (e.g., stop button, safety loop, etc.) will override the obstruction sensor and return the operator to its normal operation. " If two (2) obstructions occur, with at least one internal (e.g., an inherent obstruction such as the R.P.M sensor), the gate will not activate from any automatic system, including the built in time delay to close. Either a manual device such as a pushbutton within line of site of the gate and operator or the stop button supplied with the operator must be activated to return the operator to its normal operation. OPEN ONLY CIRCUIT Separate open circuits for line-of-sight devices and out-of-sight devices such as open loops or radio controls. LOOP CONTROL CIRCUITS Vehicle control devices such as reversing loop detectors are connected to this circuit. TIME DELAY TO REVERSE CIRCUIT Allows the gate to come to a complete stop before reversing direction. Approximately ½ second between stop and reverse. NOTE: This feature is defeated when either the inherent or external obstruction circuits are activated. Doc 01-G0665 Rev C