Chapter 6 Electromechan e r m m c a a ni cal a S Sy s st ems e s 159 9 Copyright Goodheart-Willcox Co., Inc. Copyright Goodheart-Willcox Co., Inc. Activity 6-8 Motor-Driven Timers Objectives The motor-driven timer provides a wide variety of timing actions for industrial circuit applications. In its simplest form, this timer has an electric drive motor, a ratchet release coil, and a ratchet dial that is held stationary until released. When the timing cycle reaches its set-time, the ratchet is released and the dial resets itself by spring action. Both on delay and off delay reset timers are available. More sophisticated reset timers permit a wide range of timing operations in a single unit. In this activity, a simple reset timer will be used to build a load control circuit that produces either interval or delay timing operations. Initially, when the timer is energized by the control switch, load A is turned on and load B is turned off. After the expired time setting or the time out condition has been reached, load A is turned off and load B is turned on. The action of a motor-driven timer is used to represent a type of timing application that might be used in conjunction with robotic system applications. Equipment and Materials • Reset timer (Eagle Signal HD-50 Series) or equivalent. • 7.5 W incandescent lamps with sockets (2). • SPST toggle switch. Procedure 1. Refer to the timer manufacturer’s product manual before attempting to complete this activity. 2. Wire the reset timer for the on delay operation as shown in the following. M Relay coil Timer switch Manual power switch Load A Load B NC NO Motor 120 Vac 60 Hz 7.5-W lamp 7.5-W lamp Goodheart-Willcox Publisher Reset timer with on delay operation.