Procedure Overview

In this procedure, you will design, connect and operate a time$-$delay relay in a control circuit that will simulate a timed traffic signal.

$-1.$ Solve the following design problem.

Design a control circuit that will simulate a traffic signal with a pedestrian crosswalk. The circuit should be designed so that a pushbutton switch can be pressed to cause the traffic light to immediately turn red and stay red for $20$ seconds. This will allow the pedestrians time to safely cross the intersection. After $20$ seconds, the light should change back to green.

Draw your circuit on a separate piece of paper.

$-2.$ Perform the following substeps to set up the system.

A$.$ Make sure the main power switch is off.

B$.$ Remove any test leads on the front panel.

$-3.$ Connect the circuit that you designed in step $1.$

$-4.$ Set the control knob to the $20$ second time delay.

$-5.$ Turn on the main power switch and observe the indicator lamps.

Red Lamp Status

$-($On$/$Off$)$

Green Lamp Status

$($On$/$Off$)$

The green lamp should be on and the red lamp should be off indicating that the traffic can flow through the intersection. A pedestrian cannot cross safely at this time.

$-6.$ Operate the circuit that you designed and connected.

When the pushbutton is pressed, the green lamp should go off and the red lamp should come on$.$ This will last for $20$ seconds. The lamps should then return to their previous status.

NOTE

In reality, when the pushbutton switch is activated, the traffic light will not immediately change to red but will first change to yellow for a few seconds to allow the traffic time to stop.

$-7.$ Demonstrate the circuit to your instructor.

This is part of your skills assessment.