Activity 4.4 – Logic Circuit Problems                 

Purpose

Many of your parents and grandparents will remember having to get out of their cars and open their garage doors manually. It wasn’t so bad when the weather was sunny and the temperature was a pleasant 80° but, boy, was it a pain when it was raining or snowing and the temperature was around 98°F or 15°F. You may also remember having your temperature taken using a glass thermometer instead of the digital ones that are so fast and beep when it is time to look at the reading. What made these devices possible?

The use of digital electronics and logic gates make 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 they will work as they are supposed to work.

In this lab, you are going to select the components, program the circuits, and simulate the 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.

Equipment

-    Digital electronic trainer

-    Jumper wires

-    Power supply

-    Data Sheets (10)

Procedure

1.      Working with your partner, read each problem and design logic circuits that will satisfy the design criteria. Record your progress on the activity data sheets. 

2.      Have each data sheet checked as it is completed by the teacher. After your teacher has done the checking, set up the solution on the trainer.

Conclusion

1.      List three problems that are not listed in this activity that you think could be solved using digital electronics.

2.      What role did troubleshooting play in the simulation of these problems?

3.      What are sensors, and what do they do?

4.      How can sensors be combined to make control systems?

5.      Where in everyday life are control systems encountered?

       Logic Circuit 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.      Patients need extra attention after serious operations. We would like to have push buttons for patients to use that will sound a warning at the nurse’s station only during the daytime. At night there is a different system for patients to use. Design a patient warning system that will work only during the daytime.

3.      Some hospital rooms get very warm in the summer. We need an automatic fan to cool the patients. The fan should also be able to be turned on manually. Design this 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. Be advised the manual over-ride will be turning the light on during the day BUT not off during the night. After solving circuit create a circuit that would manually turn the light off at night if you are away.

5.   Chose a problem from the cards in your kit.

6.      Ornithology deals with the study of birds. When photographing these creatures, one needs to be very careful not to scare them. Design a remote camera shutter release that will be activated when the birds land on a feeding table. The camera should only work during daylight hours.

7.      Air conditioning systems in apartments and houses are controlled by a thermostat. Design a system that will turn on the A/C system when the temperature rises above the thermostat setting. A manual control switch should also be included for continuous operation of the system.

8.      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.

9.      Many people who own cars protect them from theft and vandalism with an alarm system. Design an alarm system that will light a strobe if the car is tampered with. This alarm should remain lit until the owner deactivates the system.

10. Many homes have automatic garage door openers. These systems need to 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 someone is in danger of being struck by the moving door and that will also stop automatically at the end of its downward travel. (Hint: The system requires two logic gates.)