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CONVEYOR BASED SORTING SYSTEM COLOUR SENSOR SIGNAL CONDITIONING
This report analyses the best strategy for interfacing the colour sensor with the microprocessor by using either Comparators or Analogue to Digital Convertors (ADC) in the process. Focusing mainly on the advantages and disadvantages of these two components, we can conclude which one is more effective and responsive with cost, time taken to process the programme and reliability. Using C programming a microprocessor is programmed in order to detect the colour of the objects passed on the conveyor belt using LDR.
Analogue to Digital Convertor (ADC):
It is a system that converts the input analogue signals (from a light source or sound signal) to digital output signal by a process called quantization, which is also called as digital signal processing that is the process of mapping a large set of input values to a countable smaller set. Generally, the digital output signal is in binary number that is proportional to the input values.
Component parts of ADC:
There are seven different components within the ADC that make up the whole processing circuit which includes,
- Set-Reset latch – has 2 inputs and outputs which used as storage element in ADC
- Clock – a constant input signal that fluctuates between high and low and is used coordinate the actions of the circuit.
- AND gate – a basic logic gate which has only high inputs (1) to start the conversion when prompted.
- Counter – an electronic device which stores the number of times something occurred and used directly with the clock signal.
- DAC – to convert the digital signals to analogue output signals when commanded (reverse function of an ADC)
- DATA latch – takes the output of counter as its input and convert the analogue signals into digital outputs.
- Comparator – that compares two voltages or currents and changes its output depending on which is larger.
Advantages of ADC:
Some benefits of using the ADC in this colour sensor interfacing system with the microprocessor are listed below,
- Cheap in cost and speed varies to different ADC for example flash ADC is the fastest of all its kind.
- ADC has higher resolution than using a comparator.
- Less steps and components when it comes to programming in a microprocessor
- Clock in ADC keeps the circuit in time and provides a square wave input.
- Set-reset function allows the circuit to be functioned and keeps it in control.
- It converts any input voltages, even from 1V to 5V into a digital output (flashing LED from less bright to very bright display) through its built in components whereas in a comparator it is either 0 from 0V to 2V and 1 from 2.5V to 5V.
Disadvantages of ADC:
Also the drawbacks of using the ADC are,
- Slow in speed compared to a comparator device as ADC has more component parts than comparator.
- Each and every parts have to be earthed appropriately.
- Have to have many inputs into the encoder (for 4 bit outputs – 16 input signals and for 5 bit its double the inputs).
- ADC has several sources of errors like quantization error. These are measured in least significant bit (LSB)
Comparator is an electronic device that compares the input two voltages or currents and outputs the higher or larger (1) digital signal. It consists of a specialized high -gain differential amplifier which are commonly used in devices that measure and digitize analogue signals, such as Analogue to Digital Convertors (ADC). Comparators are also being installed within analogue to digital convertors (ADC).
Advantages of comparator:
Using the comparators in the microprocessors in the circuit can have some positive impact on the project. Some of them are,
- Cheaper in cost when comparing to other devices of amplifying.
- Comparators does not require an external power source such as additional current or voltage supply since the power comes from the processor.
- These are in ordinary working condition and very compact and robust model and are very easy to handle. Can be portable as well.
- Electrical comparators have very less moving parts and the pointer is very light and not sensitive to the vibrations.
Disadvantages of comparator:
Some of the disadvantages of using the comparators are,
- Heating of coils in the measuring unit may cause zero drift and can alter the calibration.
- If only a fixed scale is used with a moving pointer then with high magnifications a very small range is obtained, in this case it’ll be from 0V to 2V it’s low (0) and from 2V to 5V it’s high (1).
Using an Analogue to Digital Convertor would be the possible solution in this colour sensor operating system as there are more benefits from ADC than Comparator. Since ADC has higher resolution and uses two registers to record the values from their 10 bits of inputs, it is more reliable and accurate with a few quantization and bubble errors. Comparator is one of the parts in ADC and it can only be used to differentiate two or less objects as it has a maximum of two outputs but ADC has plenty.
Therefore, with ADC we can identify the three different coloured objects through this colour sensor.
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