P6g It's Logical
- Specification
- Lesson Plans
- Questions
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- Extras
State that the input signal for a logic gate is either a high voltage (about 5 V) or a low voltage (about 0V).
Describe the truth table for a NOT logic gate in door OR passenger’s door OR both doors need to terms of high and low signals.
Describe that the output of a logic gate is high or low depending on its input signal(s).
Describe the truth tables for AND and OR logic in terms of high and low signals.
Describe how to use switches, LDRs and thermistors in series with fixed resistors to provide input signals for logic gates.
Describe the truth table for NAND and NOR logic gates in terms of high and low signals.
Explain how a thermistor or an LDR can be used with a fixed resistor to generate a signal for a logic gate which depends on temperature or light conditions.
Explain how a thermistor or an LDR can be used with a variable resistor to provide a signal with an adjustable threshold voltage for a logic gate.
Objectives:
Explain the meaning of digital levels 0 and 1 in terms of volatges 0V and 5V (TTL logic levels)
Learn the symbols and truth tables for the simplest logic gates NOT, AND and OR
Two gate combinations including NAND and NOR
Prior Learning:
Digital communications
Difficult Concepts:
Appreciation of logic gates as logical devices - black boxes - that follow very simple rules.
combinations as result of 2 to the power of number of inputs ie 2,4,8,16 for 1,2,3,4 inputs AND knowing what these combinations look like.
Outline:
Go over binary the digital language. Relate this to computers as very complicated logic gate circuits. Electronics as at its simplest a means of aloowing circuits to automatically solve problems. Introduce NOT, AND and OR gates formally with truth tables. Develop two gate circuits showing the NAND and NOR gates with their truth tables and symbols.
Suggested Practicals:
MFA decision modules with cards to solve basic problems. NOTE: Do NOT lose the leads we have very few of them!
Extension Activities:
Solve more complicated MFA board problems
Find a way of building an XOR gate from NOT, AND and OR gates
Homework:
Homework1
Objectives:
Be familiar with 3 gate combinations upto and including 3 input logic gate circuits
Recognize and understand the operation of the NOR gate bistable latch circuit
Prior Learning:
Digital communications and two input logic gates
Difficult Concepts:
Intermediate steps in complex logic gate problems. Sequential logic gate circuits depend on prior state of inputs. Explanation of NOR gate latch circuit.
Outline:
Demo the relay and LED as possible outputs froma logic gate circuit. Logic gates can not supply much current and hence power to drive power outputs. Hence relay to say turn on motors in a washing machine. Go over two 3 input 3 gate logic gate circuits. Demo the NOR gate bistable latch circuit. Go over the idea of sequential logic gate circuits using timing diagrams. Understand the action of the NOR gate latch circuit. Explain as the basis of computer memory - one bistable remembers one bit of information.
Suggested Practicals:
Bread board latch circuits - suggest pre-made with LEDs for outputs on the Q output. Alternaitveley use the MFA boards with the XXX modules
Extension Activities:
MFA board progammable board to demonstrate the workings of a computer processor and memory
Homework:
Homework2 again