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ELEC3106 Electronics Lab project: metal proximity detector Objective The objective of this laboratory task is to give the students experience with a small open-ended design problem in which they can benefit from the knowledge gained throughout the course. Components For this laboratory exercise, you will need 2 Probes 1 Bread-board LEDs Logic gates Resistors Capacitors Transistors Other components Wires Lab-book Components available from the school workshop (or equivalent substitutions) may be used in this design project. Use of other components require the permission from the course coordinator. Requirements In this laboratory exercise, you need to, in pairs of two students, design and characterise a metal proximity detector which makes use of an air coil as a sensor. For example: the specific coil showed in Figure 1(a), which has a diameter of about 5cm, has an inductance of 5µH; when a sheet of metal is placed just next to this coil (parallel to the coil plane), the coil inductance drops to 3.5µH. The designed metal proximity detector must be able to detect a 5cm× 5cm metal sheet held next to (but not touching) the sensor coil and indicate to a user – for instance by means of an LED – the presence of the metal sheet. The metal priximity detector may make use of laboratory signal generators and power supplies. Other than these, there are no requirements to the design – but you may want to consider how to exceed the basic requirements by for instance 1) using a 3 V power supply as the only laboratory equipment emulating battery operation 2) measuring and displaying the distance to the metal sheet with 2 or more bits resolution or 3) making a very sensitive detector that can detect a “small” piece of metal or a metal sheet “far away”. Pre-lab work It is essential that you do your circuit designs before each laboratory class, complete with initial component values: there will only be enough time during the class to measure, optimise and debug your circuit, not designing it. Use your lab time wisely and start design early. It is probably a good idea to also assemble the circuit on your bread-board before the class. You will likely need to do some experimentation in the lab to implement a good solution or try out ideas, so be prepared for that. Think about the requirements. How do you sense the coil inductance? How do you make the sensed signal into a form that you can further work with? How do you drive your proximity indicator? Measurements In your laboratory session, carry out the measurements in this section in pairs of two students to characterise your circuit. Make sure that you show your result to the laboratory demonstrator, and that both of you record everything neatly in your lab-book. In your last design laboratory class (week 10), you must demonstrate your design to your laboratory demonstrator. Your test set-up should look somewhat like what is shown in the figure below: (a) function generator power supply metal detector internal nodes for observation probe display detector coil metal sheet (b) Figure 1: Air coil (a). Metal proximity detector measurement set-up (b). Characterisation To verify that your circuit meets the specified requirements, your circuit characterisation need to include the measurements that answers the following questions: What is the circuit power consumption? What is longest distance D (see Figure 1(b)) between coil and metal sheet you can reliably detect? How many different distance (D) can you reliably detect? What is the range of input supply voltages over which the circuit operates? You must capture CRO waveforms of voltages on suitable nodes in your circuit that demonstrate the circuit operation. It is up to you to identify which voltages waveforms on which nodes to capture to best demonstrate your design. You may want to do further characterisation, making sure that you collect suitable evidence of your characterisation. Report A short report (5 pages max) on the laboratory exercise must be prepared and uploaded as a .pdf-file on the course Moodle site by Monday week 11. The report should include answers to all questions asked above, and brief comments on the results. It should also include a brief explanation of your circuit design and reasoning for choice of component values. Make sure you point out any clever designs ideas you have employed. The full schematic of your circuit must be included in the report, not counting towards the page limit. Submit one report per two-student group and make sure that both student’s names and student ID appear clearly on the report.