Problem 6.3.4 Logic Problems

Introduction

As recently as two decades ago, people opened their garage doors manually. It wasn’t so bad when the weather was sunny and the temperature was a pleasant 80°, but it was not fun when the weather was bad. If you look in the back of your medicine cabinet at home, you might even be able to find a glass thermometer instead of a modern digital one. The glass thermometers were slower and did not beep to indicate when they had a reliable reading.

The use of digital electronics and logic gates makes it possible to have remote-controlled garage door openers and digital thermometers that are much more accurate. The challenge for manufacturers of these products is to program the devices correctly and inexpensively so that they function as expected.

Equipment

·  Transistors to Gates presentation

·  Gateway To Technology™ notebook

·  Logic Problems Data Sheets

·  Snap Circuits® components

o  2 Boards, voltage source, and power supply
o  SPDT Switch
o  1 – AND gates
o  1 – OR gates
o  1 – XOR gate
o  1 – inverter gate
o  2 – Red LEDs
o  1 – Green LED / o  1 – push switch
o  1 – slide switch
o  1 – photoresistor
o  1 – thermistor
o  1 – motion detector
o  Various lengths of snap wires
o  NOR gate (optional)

Procedure

In teams of two to three, you will design, build, and test circuits to simulate devices that will solve the problems presented. This will help you learn how input devices and output devices are connected with logic gates to produce digital electronic systems.

1.  Your instructor will assign which logic problems your team must solve.

2.  Use the Logic Problems Data Sheets to help design a solution to each problem.

3.  Create and test your solution using the Snap Circuits® components.

4.  Have the instructor verify that the circuit is working correctly. Be prepared to explain your solution and show your truth table.

5.  Photograph an image of the solution to include as a deliverable along with the Logic Problems Data Sheets.

Sensor / Conditions / Required Pull Up/Pull Down Resistor
0 / 1
/ Push Switch
/ Slide Switch
/ Photoresistor
/ Thermistor
/ Motion Detector


Logic Problems

1.  In hospitals babies sometimes need to be kept warm in incubators for a period of time after birth. Design a system that will sound an alarm if the incubator gets too cold.

2.  Ornithology deals with the study of birds. When photographing these creatures, one must be careful so as not to scare the birds. Design a remote camera shutter release that will be activated when birds land on a feed table. The camera should work only during daylight.

3.  Chicken coops get very warm in the summer. We need an automatic fan to cool the chickens. The fan should also turn on manually any time to clear the coop of nasty aromas. Design the fan control system.

4.  Mr. and Mrs. Gonzales would like an automatic system to turn their porch light on at night and off at dawn. Design an automatic lighting system with a manual over-ride.

5.  All homes should have a fire detection system for the safety of the people living there. Design an alarm system that will detect heat or smoke.

6.  A thermostat controls heating systems in apartments and houses. Design a system that will turn on the heating system when the temperature falls below the thermostat setting. A manual control switch should also be included for continuous operation of the system.

7.  A traffic signal light needs to be installed at a dangerous intersection. The light should stay green for the major highway unless a vehicle approaches from the side street.

8.  A museum is concerned about the security of their new DaVinci display. Design a burglar alarm that will turn on a light if a window slides open or if motion is detected in the room.

9.  Many homes have automatic garage door openers. These systems must have an emergency shut-off so that they can be operated without fear of injury to anyone. Design a system that can be disabled automatically in the event that someone is in danger of being struck by the moving door. The system will also stop automatically at the end of its downward travel. (Assume that the garage door motor is running, and closing the door. You are only controlling when to stop the motor - the emergency stop.)


Conclusion

1.  Write a logic problem that would require three inputs.

2.  What role did troubleshooting play in successfully solving these problems?

Project Lead The Way, Inc.

Copyright 2011

GTT – Unit 6– Lesson 6.3 – Problem 6.3.4 – Logic Problems – Page 1