Elec 4 AQA
A summary of some of the things that you need to know for AQA Elec 4 , Electronics.
- Created by: Joey
- Created on: 23-05-13 19:36
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- Elec 4 AQA
- Feedback
- Closed Loop
- Negative - Feedback reduces effect of input and ouput reaches steady point
- Postivie - Feedback increases effect of input
- Open Loop - No feedback
- Closed Loop
- Tristate Buffer
- Has three states, logic 1,0 and open circuit
- When OE (bar) is 0 it is connected
- Enables Data to be transferred when needed
- One Tristate buffer per bit
- DAC
- D0 - At bottom and is most significant with highest resistance
- Schmitt Triggers
- Two Distinct Switching Levels which can clean noisy signals and reduce multiple switching
- Upper Switching Level when Output is High
- Lower Switching Level when Output is Low
- PC Vs ANN
- Processors
- ANN - Simple but many processors
- PC - Very few but complex
- Memory
- PC - Dedicated Memory (ROM,RAM etc)
- ANN - Stores data in weightings of connections
- Program
- ANN - Trained by changing values in weightings
- PC - Follows a set of instructions hence the program
- Tasks
- ANN - Better at predictive tasks such as weather forecasting
- PC - Better at calculations such as banking
- Processors
- Data Latch - Using D-Type Flip Flops
- Obviously holds data
- One D type flip flop per bit
- Sends D to Q when CK pulse rises
- For Data Latch function only Ck connections joined together
- Conversion
- DAC
- D0 - At bottom and is least significant with highest resistance
- ADC
- Flash
- Very Fast and Expensive
- Number of Comparators = (2^N) -1
- Ramp
- Signal input is increased slowly in a ramp fashion until it is greater than the DAC output
- Slow in comparison to Flash ADC
- Flash
- DAC
- Photodiodes - Very Fast Response Compared to LED
- Optical Shaft Encoders
- Resolution - Minimum angle that can be turned through with change
- Optical Shaft Encoder can be used for Direction, Speed and absolute position
- Slotted Disk can be used for angular speed and relative position
- Stepper Motors
- 1.8 Degrees for 6 pole motor and 7.5 Degrees for 4 pole motor
- Less Torque and Speed of rotation than conventional motor
- Needs control electronics to continuously apply current to each choil
- Illumination
- Seven Segment Display
- Normal calculations apply to each segment
- Dot Matrix Display
- Multiplexed
- Dimmer as only on 1/5th of the time
- LED's lit via rows and columns
- Can display a range of characters
- Seven Segment Display
- Feedback
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