Developing A Computer-Based DAQ Measurement System For A SMA ✓ Solved

Developing a computer-based DAQ measurement system for a Smart Home

If you like to develop a computer-based DAQ measurement system or that can provide several functions in a Smart Home System , such as climate control or gas leakage detection functions, answer the following for the climate control system function: 3.1 Draw the hardware connections of the system focusing on the pin connections of the system components, so that the system can provide the 'Climate Control' function. The available devices are: (5 marks) Microprocessor-based system (Laptop/PC). Interface board: NI USB DAQ. LM35 Temperature sensor Humidity sensor Micro-switches Variable resistor LEDs Relays Multi-output power supply Include any required passive electronic components 3.2 Draw a flowchart for a program that can achieve both the climate control and gas leakage detection functions. (4 marks) 3.3 What are the factors that should be considered when selecting a DAQ card? (4 marks) 3.4 Discuss the signal aliasing problem and how you can overcome this effect; support your answer with figures and drawings (2 marks) 3.5 What are the steps of conversion of continuous signals to digital values (ADC)? (2 marks) 3.6 Name four types of ADC’s and choose any two to compare between them; what is the ADC type that is used in NI DAQ’s? support your answer with figures and drawings (7 marks) 3.7 Compare between RTD (Resistance Type Device) and Thermocouples temperature sensors; support your answer with examples and drawings. The LM35 sensor can be classified as which type of temperature sensors? (5 marks) 3.8 Give examples of DAQ cards that can be used to measure the following properties and discuss the reasons for your selection.? 1- Displacement 2- Vibration 3- Strain (6 marks) Total 35 marks 4: You are to develop a home security system that can be used to monitor a house of two doors and four windows. The output of the system should present the status of each location independently and should provide an audible warning in case of any problem - including the detection of smoke. The available devices are: − PIC16F877 Microcontroller (given in Figure 4.1) − two door push button switches − four window push button switches − one Motion Detector − one smoke detector sensor − eight LEDs − one buzzer − Include any passive electronic components required. According to your study answer the following questions: 4.1 Draw a block diagram for the complete system. (4 marks) 4.2 Using the PIC16F877A microcontroller shown in Figure 4.1, draw the wiring diagram of the proposed system. Include any necessary electronic components required for the microcontroller to function correctly; state the function of each element. (8 marks) 4.3 Draw a flowchart for a program that can achieve the above function. (4 marks) 4.4 Given the pin configuration of the PIC16F877A microcontroller (shown in Figure 4.1), describe the function of the following: (4 marks) __________ __ · MCLR · OSC1/OSC2 - RA0 - RD5 ( Figure 4.1)

Sample Paper For Above instruction

The development of a computer-based Data Acquisition (DAQ) measurement system is fundamental in enhancing smart home technologies, especially for functions such as climate control and gas leakage detection. This paper discusses the design and implementation considerations for such a system, focusing on hardware connections, programming logic, data acquisition principles, sensor selection, and property measurement devices. Additionally, a practical home security system implementation using a PIC microcontroller is presented, highlighting the integration of sensors, control units, and alarms.

Hardware Connections for Climate Control System

The hardware setup for a climate control system centered on a DAQ interface requires meticulous pin connection mapping. The system's main components include a microprocessor-based system (laptop/PC), a National Instruments USB DAQ interface, sensors, switches, indicators, and relays. The NI USB DAQ acts as the bridge between analog signals from sensors and the digital domain for processing.

The LM35 temperature sensor outputs an analog voltage proportional to the ambient temperature, connected to an analog input pin (AI0) of the NI DAQ. Similarly, a humidity sensor provides an analog or digital output linked to another analog input (AI1). Micro-switches for manual override or system control are connected to digital input pins (for example, Port D pins). Variable resistors (potentiometers) are attached to analog inputs to calibrate sensor readings, while LEDs serve as visual indicators connected to digital output pins. Relays, driven by digital output pins, control the HVAC system or fans.

Passive components such as resistors and capacitors are incorporated where necessary to filter signals, limit current, or provide biasing. For instance, series resistors protect LEDs, and filtering capacitors stabilize sensor readings. The multi-output power supply ensures stable voltages compatible with sensors and actuators, typically 5V or 12V.

Flowchart for Climate Control and Gas Leakage Detection

The program initiates by initializing system components and setting thresholds for temperature, humidity, and gas levels. It continuously reads sensor data from the DAQ. If the temperature exceeds a set point, the system activates relays to turn on cooling devices; if below, it activates heating. Humidity sensors trigger dehumidifiers or humidifiers based on readings. Gas leakage detection sensors raise alarms and activate ventilation if dangerous gases are detected.

The flowchart involves decision blocks at each sensor reading to compare current values against thresholds. Actions are performed based on these comparisons, and system status indicators are updated accordingly. The process repeats in a loop, ensuring real-time control.

Factors in DAQ Card Selection

Selecting an appropriate DAQ card involves evaluating several factors: input/output channels required, resolution and accuracy, sample rate, communication interface, compatibility with existing hardware/software, and cost. The application-specific requirements dictate the choice—high-resolution measurements for laboratory purposes or faster sampling for dynamic processes. The DAQ's electrical characteristics, such as input impedance and supported voltage ranges, must match sensor specifications.

Signal Aliasing and Prevention

Aliasing occurs when continuous signals are sampled at a rate lower than twice their highest frequency component (Nyquist rate), causing distortion and misinterpretation of the signal. To prevent aliasing, anti-aliasing filters (low-pass filters) are employed before sampling, removing high-frequency components above the Nyquist frequency. Additionally, increasing the sampling rate ensures that the sampled data accurately reflects the original signal's frequency content.

[Insert figure illustrating aliasing and anti-aliasing filter].

Steps in Analog-to-Digital Conversion

The ADC process involves sampling the continuous signal at discrete time intervals, quantizing the sampled voltage levels into finite digital steps, and then encoding these levels into binary form. The steps are: 1) Sampling, 2) Holding the signal, 3) Quantization, 4) Encoding into binary data.

Types of ADCs and Comparison

Common ADC types include Flash, Successive Approximation, Sigma-Delta, and Pipe-lined ADCs. For example, Flash ADCs are very fast but require many comparators, suitable for high-speed applications. Successive Approximation ADCs provide a good balance of speed and accuracy, commonly used in data acquisition systems. The NI DAQ employs Successive Approximation ADCs owing to their efficiency and precision.

[Insert diagrams comparing ADC architectures].

Temperature Sensors: RTD vs Thermocouples

RTDs (Resistance Temperature Detectors) operate on the principle of resistance change with temperature, typically made of platinum. They are known for high accuracy and stability within a limited temperature range. Thermocouples generate a voltage based on the Seebeck effect and can measure extremely high temperatures, though with less precision. For example, RTDs are used in industrial process control, whereas thermocouples are suitable for furnaces.

The LM35 sensor is classified as an integrated circuit temperature sensor, producing a predictable voltage output proportional to temperature, similar to thermocouples but with greater linearity and ease of calibration.

DAQ Cards for Measuring Various Properties

For displacement measurements, linear variable differential transformers (LVDTs) are paired with high-resolution DAQ cards like the NI 9219. Vibration sensors utilize accelerometers connected to cards with high sampling rates such as the NI 9205. Strain measurements are performed using strain gauges connected to Wheatstone bridges and processed through DAQ modules like the NI 9237, designed for precise strain and load measurement.

Home Security System Design

The security system comprises a microcontroller (PIC16F877A), sensors, switches, LEDs, and alarms. The block diagram includes power supply, sensor inputs, microcontroller, status indicators, and output alarms. The wiring diagram involves connecting door and window switches to digital inputs, motion and smoke sensors to analog or digital inputs, LEDs as status indicators, and a buzzer for alarms. Passive components like resistors and diodes are added for signal conditioning and protection.

The system operation involves continuously monitoring sensor inputs. Upon detecting an anomaly such as door opening, window breach, motion, or smoke, the microcontroller activates corresponding LEDs and the buzzer, providing real-time alerts. The program flow includes initialization, continuous sensor reading, decision-making for alarms, and reset procedures.

Microcontroller Pin Functions

The PIC16F877A features multiple pins serving various functions. The MCLR pin is used to reset the microcontroller; applying a high voltage resets the device. The OSC1/OSC2 pins connect to an external crystal oscillator, providing clock signals essential for timing operations. RA0 is an analog input pin used for sensor data acquisition, while RD5 is a digital I/O pin used for controlling outputs such as LEDs or relays. Proper configuration of these pins is critical for system functionality.

In conclusion, integrating DAQ systems and microcontrollers in smart home applications requires careful hardware design, programming, and understanding of sensor characteristics. Proper selection of components and understanding signal processing limitations ensures robust and effective system performance.

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