ICT 0417 – Types and Components of Computer Systems
1. Types and Components of Computer Systems
Objective
Know and understand the need to convert digital data to analogue data so it can be used to control devices.
1.1 Introduction
Modern computer systems process information in digital form – a series of 0s and 1s. Many real‑world devices (motors, speakers, sensors, etc.) operate using continuous analogue signals such as voltage, current, or sound waves. To interact with these devices, computers must translate their digital output into analogue signals and, conversely, translate analogue inputs into digital data.
1.2 Why Conversion is Required
Physical limitation: Most actuators and transducers respond to continuous changes in voltage or current, not discrete binary values.
Human interface: Human senses perceive analogue phenomena (sound, light, temperature). To produce audible sound or display brightness, digital data must be rendered as analogue signals.
Compatibility: Legacy equipment and many industrial control systems were designed before digital electronics became prevalent.
1.3 Digital vs Analogue
Aspect
Digital
Analogue
Representation
Discrete binary values (0,1)
Continuous range of values
Noise tolerance
High – errors can be detected and corrected
Low – small disturbances affect the signal
Storage
Memory chips, hard drives
Physical media (e.g., magnetic tape) or none
Typical uses
Computation, data processing
Audio output, motor control, sensor reading
1.4 Types of Data Conversion
1.4.1 Digital‑to‑Analogue Converter (DAC)
A DAC receives a binary number and produces a proportional analogue voltage or current. The basic relationship can be expressed as:
where Vref is the reference voltage, D is the decimal value of the binary input, and n is the number of bits.
1.4.2 Analogue‑to‑Digital Converter (ADC)
An ADC samples an analogue signal at regular intervals (sampling rate) and quantises each sample into a binary value. Key parameters include:
Sampling frequency (Hz)
Resolution (bits)
Quantisation error
1.5 Practical Examples of Digital‑to‑Analogue Conversion
Audio playback: Digital audio files are sent to a DAC, which creates a varying voltage that drives a speaker diaphragm to produce sound.
Motor speed control: A microcontroller outputs a Pulse‑Width Modulated (PWM) signal; a low‑pass filter and DAC convert this into a smooth voltage that sets motor speed.
Display brightness: Graphics data are converted to analogue voltage levels that control the intensity of LCD backlights.
1.6 Process of Converting Digital Data to Analogue Signals
Generate binary data representing the desired output (e.g., audio sample).
Feed the binary word to a DAC.
The DAC produces a stepped analogue voltage proportional to the binary value.
If a smooth waveform is required, pass the stepped output through a low‑pass filter.
The filtered analogue signal drives the target device (speaker, motor, etc.).