University of Arkansas - AgriScience Project

AGRISCIENCE EXERCISE

PHYSICAL SCIENCES IN AGRICULTURE

Key Concept: Electricity and Electronic Systems

Sub-Concept: Electronics Applications

Agricultural Application: Basic electronics principles are applied in common agricultural equipment.

Exercise: Constructing a Silicon Controlled Rectifier (SCR) Switching Circuit.

Applied Principle(s): Basic principles of electricity

Goals:

  1. Be able to read and electronic circuit schematic.
  2. Assemble a temporary SCR switching circuit that will function as specified.
  3. Explain the operation of the circuit.
  4. Describe possible applications.


Materials: (per group)



References: Attached information sheet

Procedures for Conducting the Activity:

1. Divide the class into small groups of no more than 3 students each.

2. Provide each student with an instruction/data sheet, and allow the class time to read the entire activity and attached information sheet before proceeding.

3. Provide each group with the necessary materials.

4. Allow the students to proceed through the activity, providing assistance as necessary.

5. When all groups have finished, discuss the activity questions and results as a class. Discuss the practical applications of the knowledge gained through the activity.

AGRISCIENCE EXERCISE

- Constructing a Silicon Controlled Rectifier (SCR) Switching Circuit -

Student Data/Instruction Sheet

1. Read the attached information sheet before proceeding through this exercise, to gain a better understanding of the relationships that exist.

2. Secure the following equipment and supplies:

3. Assemble the SCR switching circuit as indicted in the circuit schematic shown below.































4. Test the circuit as indicated:

A. Momentarily closing the NO switch should place the SCR in the conducting mode and cause the lamp to glow. Try this with your circuit. Does the lamp glow? YES NO

B. Momentarily opening the NC switch will return the SCR to a non-conducting mode and cause the lamp to go off. Try this with your circuit. Did the lamp go off? YES NO



C. Switch the lamp on again. Disconnect the conductor leading to the NO switch from the positive terminal of the battery. Disconnect the conductor attached to the 'gate' terminal of the SCR. What effect did these modifications have on the operation of the lamp?









5. Disassemble the circuit and return the components to storage.

6. Develop a hypothesis about the operation of a silicon controlled rectifier based on your experience with and observations of this circuit.







7. Develop a written plan of research procedure to test your hypothesis.















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