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GCSE: Systems and Control
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The aim of this investigation is to build and test a sensor, and explaining the characteristic of a sensor and then designing and assembling a measurement system, and using the sensor to make a measurement.
Hence, the whole idea was changed to monitoring airflow. The problem was the method of measuring it: (2) Initially, I presumed that I could use a rotary potentiometer to measure the airflow 'power.' However, it was apparent that there was too much friction within the rotary potentiometer; hence a strong wind power would be needed to cause movement in the rotary potentiometer, which the fan could not produce. We were unable to find an equipment in the laboratory suitable for this, expressing the limit to the investigation.
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In this case I have used a potential divider comprising of an LDR and a fixed resistor. I have used two components that have very similar resistances to maximise the sensitivity of the sensor, as shown in the preliminary experiment carried out. The LDR is a resistor, which varies in resistance according to the intensity of visible light it is exposed to. In the case of the LDR used for this investigation, resistance decreases as the illumination intensity increases. This type is normally composed of either cadmium sulfide or silicon. Light Dependant Resistors are often used as switches in apparatus such as street lights, which turn on at dusk and off at dawn.
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I can take a reading through the potentiometer which will be proportional to the position of it. To take the readings I will have to connect up the potentiometer in a circuit. Because it is a potentiometer there are three terminals. With these terminals voltage is fed into one terminal at 5V and 0V into another. The third terminal is the output and will be connected to the 0V rail through a voltmeter which will give the readings required. The circuit will be set up as follows: With this circuit the voltage flowing through the voltmeter will vary from 0-5V depending on how far in the linear potentiometer is pushed therefore the system can be easily tested to see what voltages the different thicknesses give.
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If you have a standard 8-ohm speaker then Rx is 67 ohms. The nearest value is 68 ohms. So for a 8 ohm loudspeaker Rx is 68 ohms. For a 4 ohm loudspeaker Rx is 71 ohms, for a 25 ohm loudspeaker Rx is 50 ohms, etc, etc. BUT, the Rx value is not very critical. It is just there as some sort of volume control. Experiment with it. C2 and C3 are 0.01uF (10nF) and a simple ceramic type will do the job. I tested the circuit at 9, 12, and 15 volt.
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Needless to say it took me a lengthy period of time to solder every component. The casing wasn�t as tricky for me to make. Two of the boxes I made were for two separate teams in a pub quiz and both contained of just a large push-button. The main box was designed for the referee of the game to monitor who answered the questions first, and consisted of the main circuit, an on/off switch and a reset switch. To make the main box I took five pieces of acrylic and sawed them to the right size.
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I now have my idea and the specific apparatus I need to start planning the experiment. Planning: Apparatus: Power supply Resistor Multi-meter Wires Weights G-clamp Strain Gauge Diagram of Double-sided Strain Gauge in action In order to make a sensor that can weigh items, I assumed I needed to make the circuit that would give me a voltage output. I had studied the circuit for a potential divider and so I am familiar with the design. It needs two resistors, I knew one was from the strain gauge and thought the other was for a fixed resistor.
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I have also found out that the waves received will still have a low amplitude so therefore a low voltage so a form of amplification is needed. The next slight hitch I found was that the vibrations from the transmitter were also being received along with the pressure waves, to limit this I mounted the ultra sound devices in a piece of polystyrene. I also need to proceed with another investigation in to how the ultra sound works exactly with real results.
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For this section of coursework I decided to undertake the task of building and testing a sensor. The sensor, which I built, was a thermocouple, I built this to take measurements of the temperature of a certain window.
The free end of each similar wire is connected to a voltmeter. One of the junctions is maintained at a constant temperature and the other junction is used as a temperature probe. The meter reading changes according to the difference between the temperature of the probe and the reference junction. Because the probe is no more than a junction between two thin wires, it can respond rapidly to change of temperature and has therefore a faster response time than a liquid-in-glass thermometer. A liquid glass thermometer relies on the expansion or contraction of mercury this takes a lot of time.
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But if someone enters the room it will also automatically switch on. 4. A transducer driver gives extra power so that the bulb can light very well. 5. Bulb works like so... an electrical current flows through the wire in the bulb so fast that it produces heat and light energy. Block diagram: Power supply Light sensor Unit Transducer driver Inverter Bulb This is how the whole circuit device works The power supply, which is the main sour of power, is connected to the light sensor, that is the sensor that senses the light around the area.
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The use of my system will be to regulate and maintain a constant temperature within the green house. How I aim to do this: Firstly, I would have to calibrate the values of the sensor according to temperature. This is to make sure that the system of mine would know when to open the green house window and when to close it. How the window would open? To open and close the window of the green house, the output of my circuit should be a motor. Therefore, when the output to my circuit is high, the motor will activate and as a result open the window.
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The alarm should prevent theft of the bicycles accessories (eg. lamps). 3. The alarm should have an anti-tamper trigger to prevent the alarm from being de-activated by unauthorised persons entering the housing. 4. The alarm should have an automatic time out reset to reset the alarm after a time has past, in case of a false triggering. 5. The alarm should be de-activated by use of a PIN number which can be changed by the user. 6. The alarm must have a indication of the batteries voltage level to warn the operator of a flat battery.
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However the ability to enjoy a cinema-like atmosphere in your own home with technologies such as 'Dolby Surround Sound' widescreen televisions and crystal clear picture quality is highly convenient and enjoyable as a whole. In the manufacturing industry electronics has made a massive impact on the mass-production of items and the ability to design more precise and intricate productions. Robots are now widely used for car assembly, extremely efficient and reliable, and also cheap in regard to that of employee's wages.
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4.0 Method A potential divider will be placed in the middle of a 25cm long ruler at 12.5cm. A hole needs to be drilled through the centre on the ruler at 12.5cm to attach and hold the potential divider. To the left-hand side of the ruler a small hole will be used to thread some wire through to produce a pivot. At the opposite end of the ruler two holes will be drilled. The hole at the top right will be drilled to hook the spring onto, then at the bottom right to attach the weights to. Two clamp stands will hold the ruler at a height where the weights will not touch the surface when 10N are applied.
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4.57 4.39 4.06 3.50 2.67 1.78 1.05 180 4.60 4.43 4.15 3.65 2.88 1.98 1.22 200 4.65 4.52 4.28 3.82 3.09 2.18 1.37 220 4.68 4.56 4.32 3.90 3.20 2.30 1.48 240 4.71 4.60 4.38 3.99 3.31 2.42 1.57 260 4.73 4.62 4.41 4.05 3.40 2.53 1.67 280 4.73 4.62 4.42 4.05 3.41 2.55 1.69 300 4.70 4.59 4.38 4.02 3.38 2.53 1.67 I took three sets of results. They were all exceptionally similar. As such, they have been compiled into one single table, which is the average of the three results for each resistor at each value.
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An electronics firm wishes to introduce a range of low cost alarms. You have been asked to design and produce a prototype for further development by the firm.
* It must be battery powered. Research Sensing people entering the front or rear door As the task analysis shows there are many ways of sensing people coming through a doorway. I built them all using SYSTEM ALPHA to ensure that: * They work * I know how they work. I have decided to use the upside down switch unit with a proximity detector to sense if the rear door is opened. I have decided to use a switch unit with a pressure pad to sense if the front door is opened.
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* Changes in room temperature may cause variable characteristics in the experiment. Changes in temperature may affect several items such as the efficiency of the rotary pump and the viscosity of the air travelling through the system. * Due to the nature of the apparatus set-up there are a number places where air may escape. These are mainly where valves and couplings are located, such as the air inlet valve, the main valve and couplings to the pipe, manometer, vacuum chamber and vacuum pump.
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circuit latch so that they can light their light and sound their buzzer but will not let the other team do the same. The output voltage oscillator is the part of the circuit that makes the noise, the value of the capacitor can be changed so that the buzzer makes a different noise for each team so that the team is easy to recognise. The monostable multi-vibrator is the part of the circuit that controls how long the buzzer is on for.
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The battery though must be easily accessible for maintenance purposes. The best material to construct the casing from would definitely be some type of plastic and this has to be waterproof and easy to clean. The plastic would have to blend in with the interior, not making its presence too obvious. I would say that this specific product should not be too expensive to produce and easily applied. The product is odourless and silent when not in use and can in no way harm or taint food stored in the refrigerator and does not emit any harmful rays or gasses, so it is also environmentally friendly.
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If you have different shades of grey they must reflect different amounts of light into your eyes. To test this I have designed a sensor to see that this is true. The sensor uses an LDR or light dependent resistor to see the intensity of light reflected. An LDR changes resistance depending on the amount of light on it. The circuit that I will be using is a potential divider circuit. A potential divider circuit is where two or more resistors in series split the voltage between them in a ratio of that to the resistance. If they both have the same resistance then the voltage will be the same across both of them (half of the
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I will put two contacts in my circuit so the processor can compare the resistance of the water. The second is an Op-Amp so as the resistance of the water increases the Op-Amp will change its output. The third sub-system is the output; I will use a chip that will turn on a specific LED depending on the voltage going into it. But this chip only allows one LED to be on at one time; this will reduce the amps used and make the circuit last longer on a single battery supply. The circuit can be split into separate blocks, like the Op-Amp.
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Run the light sensor attached to the rotary motion sensor across the diffraction pattern to detect the intensity of light at different positions along the pattern. 4. Record the displacement measured by the rotary motion sensor and the intensity of light measured by the light sensor. Data Laser wavelength - 6.7x10-7 meters Distance from the slit to the light sensor - 0.72 meters Single slit diffraction pattern with a 2x10-5 m wide slit Single slit diffraction pattern with
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Design a make a product which is a warning device, which would be attached to my bag so that drivers of vehicles would be aware of my presence. The device should be safe to use and manufacture.
* It should be relatively easy to manufacture Problem 3 Light Alarm On various nights during the week lights have been left on during the night and this causes a problem as it increases the electricity bill. The light sometimes may not even be turned off till about 12:00am depending on the day Problem Analysis Problem 3 * It should warn the user when the lights are left on after a certain time * It should turn the lights off if the alarm has not been responded too.
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Also to prevent the child form messing with the circuit. Function To be durable yet aesthetically pleasing to the customer. This will increase the life span and awareness of the product. Performance I will create a simple, but effective packaging and therefore, there should be no faults. The main function of the casing is to protect the PCB as it is fragile. The case will be of a simple design, which should be less errors with its overall function. Quality Requirements The packaging is required to have a high quality finish, therefore it must have smooth edges and rounded corners.
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Therefore, the product, will be beneficial for night time trips to the bathroom as there will be no need for the child to fumble around for the light switch and no longer will the child feel scared to go to the bathroom in the middle of the night. The night light will also be beneficial for children who need a light to help them sleep or children who prefer to sleep with the lights on. Children will feel more secure, during the night and reduce worries of parents/guardians, as they will be reassured their child is sleeping safely.
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Also lantern and car can used, however there are less portable and heavier. One major advantage using batteries over mains power is, the counter can be used anywhere. Batteries Zinc Carbon ? One of the most basic batteries also it?s a cheaper alternative to the alkaline. This batteries isn?t suitable for projects that require high output also the voltage drops during use. Alkaline ? The most commonly used battery and longer life than the zinc carbon batteries.
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