Project 4.1.3 State Machine Design: Elevator Door (FT-DLB)

Project 4.1.3 State Machine Design: Elevator Door (FT-DLB) Introduction

Congratulations, you have just been hired by the Otis Elevator Company. Otis has been designing elevators for over 150 years. The company is world-renowned for innovative designs and possesses a strong safety record. As with all new hires, you have been assigned to work with a senior engineer who will be your mentor. Your mentor’s name is Ed Ginner. Mr. Ginner has just completed the design for a simple state machine that controls the opening and closing of an elevator door. He has assigned you the task of implementing this state machine in a Field Programmable Gate Array. The state machine has four inputs and four outputs.

Inputs  Open_Switch (OS): This input is activated by the user. When the switch is pressed, it outputs a logic zero and causes the door to open. This input switch is located on the test fixture.  Close_Switch (CS): This input is activated by the user. When this switch is pressed, it outputs a logic one and causes the door to close. This input switch is a pushbutton switch on the DLB.  Open_Limit (OL): This input is activated by the door mechanism when the door is fully open. When this input switch is pressed, it outputs a logic zero. It is located on the test fixture.  Close_Limit (CL): This input is activated by the door mechanism when the door is fully closed. When this input switch is pressed, it outputs a logic zero. It is located on the test fixture.

Outputs  Motor_Open (MS): This output is a logic one. It will cause the door to open.  Motor_Close (MC): This output is a logic one. It will cause the door to close.  Door_Open (DO): This output is connected to an LED on the DLB and is on when the door is fully open.  Door_Closed (DC): This output is connected to an LED on the DLB and is on when the door is fully closed.

© 2014 Project Lead The Way, Inc. Digital Electronics Project 4.1.3 State Machine Design: Elevator Door (FT-DLB) – Page 1 Shown below are photographs of the front and back views of the Elevator Door test fixture. You will use this fixture to verify that your design is working.

Elevator Door Test Fixture – Back View

Elevator Door Test Fixture – Front View

The block diagram/schematic shown below shows how to interface the Elevator Door test fixture with the DLB. The L298 is an H-bridge driver designed to accept standard TTL logic levels and drive DC motors. The SN754410 Quadruple Half-H Driver can be used as an alternative to the L298.

To protect the DLB, it is important to use an EXTERNAL power supply for the 9V necessary to drive the motor. Check that your external power supply and DLB share a common ground.

Equipment Paper and pencil Circuit Design Software (CDS) Xilinx Programming Software (XPS) Digital Logic Board (DLB) L298 H-Bridge Driver Three 12kΩ resistors Fischertechniks® Elevator Door Kit Variable power supply Jumper wire

Procedure

Design Using the attached notes from Mr. Ginner’s engineering notebook as a starting point, design a state machine that will control the opening and closing of the Elevator Door. This state machine will be implemented in the FPGA on the DLB.

Simulation © 2014 Project Lead The Way, Inc. Digital Electronics Project 4.1.3 State Machine Design: Elevator Door (FT-DLB) – Page 2 Simulate the design in the CDS using the interactive digital constant for the switches and probes to represent the outputs. When running the simulation, remember that for OS, OL, and CL, a logic zero means that the switch is activated. Start the simulation with CL activated (logic zero), OS and OL not pushed (logic one), and CS not pushed (logic zero). This will simulate the door closed and no buttons pushed.

Prototyping Use the Digital Logic Board (DLB) and the Elevator Door test fixture to build and test your Elevator Door state machine design. Verify that the circuit is working as designed. If the circuit is not working properly, review your design work and circuit implementation to identify your mistake. Make any necessary corrections and retest. Be sure to document all changes in your engineering notebook. Suggestion: Turn the DLB’s RotCLK a full turn to the right after programming the FPGA chip.

Conclusion Using your engineering notebook as a guide, write a conclusion (minimum 250 words) that describes the process you used to design, simulate, and build your Elevator Door state machine. This conclusion must include all of your design work, preliminary and final schematics, a parts list, and a digital photograph of your final circuit. The documentation should be complete enough that another student, with that same knowledge of digital electronics, could reproduce your design without any additional assistance.