Monitoring Ladder Logic On/Off Status. Application Note 51308

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1 Monitoring Ladder Logic On/Off Status Application Note 51308

2 WARNING DANGER OF DEATH OR PERSONAL INJURY WARNING FOLLOW INSTRUCTIONS Read this entire manual and all other publications pertaining to the work to be performed before installing, operating, or servicing this equipment. Practice all plant and safety instructions and precautions. Failure to follow instructions can cause personal injury and/or property damage. WARNING OUT-OF-DATE PUBLICATION This publication may have been revised or updated since this copy was produced. To verify that you have the latest revision, be sure to check the Woodward website: The revision level is shown at the bottom of the front cover after the publication number. The latest version of most publications is available at: If your publication is not there, please contact your customer service representative to get the latest copy. WARNING OVERSPEED PROTECTION The engine, turbine, or other type of prime mover should be equipped with an overspeed shutdown device to protect against runaway or damage to the prime mover with possible personal injury, loss of life, or property damage. The overspeed shutdown device must be totally independent of the prime mover control system. An overtemperature or overpressure shutdown device may also be needed for safety, as appropriate. WARNING PROPER USE Any unauthorized modifications to or use of this equipment outside its specified mechanical, electrical, or other operating limits may cause personal injury and/or property damage, including damage to the equipment. Any such unauthorized modifications: (i) constitute "misuse" and/or "negligence" within the meaning of the product warranty thereby excluding warranty coverage for any resulting damage, and (ii) invalidate product certifications or listings. CAUTION POSSIBLE DAMAGE TO EQUIPMENT OR PROPERTY CAUTION BATTERY CHARGING To prevent damage to a control system that uses an alternator or battery-charging device, make sure the charging device is turned off before disconnecting the battery from the system. CAUTION ELECTROSTATIC DISCHARGE Electronic controls contain static-sensitive parts. Observe the following precautions to prevent damage to these parts. Discharge body static before handling the control (with power to the control turned off, contact a grounded surface and maintain contact while handling the control). Avoid all plastic, vinyl, and Styrofoam (except antistatic versions) around printed circuit boards. Do not touch the components or conductors on a printed circuit board with your hands or with conductive devices. IMPORTANT DEFINITIONS A WARNING indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury. A CAUTION indicates a potentially hazardous situation which, if not avoided, could result in damage to equipment or property. A NOTE provides other helpful information that does not fall under the warning or caution categories. Woodward Governor Company reserves the right to update any portion of this publication at any time. Information provided by Woodward Governor Company is believed to be correct and reliable. However, no responsibility is assumed by Woodward Governor Company unless otherwise expressly undertaken. Woodward 2007 All Rights Reserved

3 Application Note Monitoring Ladder Logic On/Off Status Monitoring Ladder Logic On/Off Status 1111 This Application Note details a method of monitoring the on/off status of the Ladder Logic block for TMR systems that use Ladder Logic. This addresses the issue described in Service Bulletin pertaining to the monitoring the LL_VALUES.RUNNING output use in Ladder Logic. Refer to Figure 1 below. 1. Create a Ladder Logic rung that toggles after every pass through Ladder Logic. This is the LADDER.LL_VALUES.MW_B_1000 line shown below. This BOOLEAN then creates a square wave in the Ladder Logic program (TRUE-FALSE-TRUE-FALSE-TRUE, etc). When the Ladder Logic program is stopped, the toggling stops. The watchdog is designed to detect this. 2. Create and connect the Ladder Logic blocks as shown below. Verify that the DLY_TIME input is longer than period of the toggle frequency. 3. Instead of monitoring the LL_VALUES.RUNNING output, the output of the LL_NOTRUN.NOT block is monitored to determine the on/off status of the Ladder logic. Figure 1. GAP / Ladder Logic Interface Woodward 1

4 Monitoring Ladder Logic On/Off Status Application Note When Ladder Logic is running, the output of the LL_NOTRUN.NOT block will be FALSE. This is because the outputs of the WAT_ON.DELAY and WAT_OFF.DELAY blocks will be FALSE since when toggling the TRIGGER, the DLY_TIME value will not allow the output to go TRUE before a new TRIGGER input. These outputs result in WAT_DOG.NOR becoming TRUE, and when ANDed with LL_VALUES.RUNNING TRUE, result in a TRUE value out of RUN_AND.AND. This value is then inverted to get the resulting FALSE output of the LL_NOTRUN.NOT. When Ladder Logic is not running, the LADDER.LL_VALUES.MW_B_1000 will stop toggling. This means that either the output of WAT_ON.DELAY or WAT_OFF.DELAY will be high, but not both because of the NOT_ON.NOT block inversion. The WAT_DOG.NOR output will now be FALSE, which makes the RUN_AND.AND result FALSE. This results in a TRUE value on the output of LL_NOTRUN,NOT. Note that this case is independent of the RUNNING output of the Ladder Logic Interface. The output of LL_NOTRUN.NOT may now be used to determine if Ladder Logic is running. A TRUE value output indicates Ladder Logic is NOT running, while a FALSE value indicates that Ladder Logic is running. 2 Woodward

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Application Note 51250 (Revision A) Original Instructions. Visual C++ Installation

Application Note 51250 (Revision A) Original Instructions General Precautions Read this entire manual and all other publications pertaining to the work to be performed before installing, operating, or