Aspects of Physics in the Grove leisure Centre Essays

Aspects of Physics in the Grove leisure Centre Essays Aspects of Physics in the Grove leisure Centre Essay Aspects of Physics in the Grove leisure Centre Essay The purpose is for the doors to open automatically when anyone is a certain distance from the door. The distance should be right for when they are walking up to the door so it has enough time to open when the person is close enough to go through it. The automatic door is needed for disabled access as it is a legal requirement. The grove has had them since the year 2000 because legal reasons state that all public places have to have access for disabled people. It makes it a lot easier for school parties, so the teacher doesnt have to hold the door so they can make sure the children at the front of the queue are looked after and not left unattended. Some people who are medically referred to the leisure centre by their doctors might be very weak and wouldnt be able to open a door, so an automatic door overcomes this problem. Another helpful thing is that the doors will not be left open in winter time, and therefore will not let heat out, which in turn will save money as the building will not need excess heating because heat is being lost. Pool Lighting The lights are not located directly above the swimming pool, the main reason for this is that it would be extremely hard to fix and change them; another reason is that if the lights were directly above the pool then condensation would cause the lights to break. This helps to spot any foreign object in the pool, as if there was a dark pool they not be spotted and if there was someone under water drowning it would make it harder for the lifeguard to spot them the less light there is. Also simply to help people to see when they are swimming on the surface or underwater as the more light there is it makes it clearer to see. The above diagram shows a light beam coming from lights set in the floor travelling upwards and reflecting at a 90à ¯Ã‚ ¿Ã‚ ½ angle to another reflecting surface, and then it does another reflection at 90à ¯Ã‚ ¿Ã‚ ½ down to the pool. The above diagram shows a light ray reflecting and how it does it, this is what the ray does in the pool lighting system. How the automatic door system works The doors work by using a passive infrared detector (P.I.R) They call it passive as it only receives infrared waves of a certain frequency and it doesnt emit any. Infrared rays are rays that are emitted by any object which is warmer than 0 K, but so the door isnt opened for animals the passive infra-red detector is tuned to detect the frequency of infrared ray that humans emit and filter out any others, also if it didnt then on a sunny day the doors would be open all of the time. The infrared radiation goes through a window which is located on the housing of the P.I.R. The window is made so that it allows infrared rays to pass through but then doesnt allow visible light through. Infrared rays go through a window in the housing of the detector, the window is made of a material which doesnt let visible light through but does let infrared through. When the passive infrared detector detects many infrared rays the fresnel lens focuses the beam on to a crystal which is usually a semi-conductor, then the electromagnetic radiation sets up a voltage which then causes a current to flow through a relay circuit, then operating a motor which is attached to the doors, then they open. The sensor is capable of reading a wide range of radiation so a filter is put over it so it limits incoming radiation to between 8 and 14mm which is the most sensitive to human body radiation. Pressure pads may be used along with the P.I.R., this is because if there is a very low change in infrared, e.g. if someone was to walk slowly up to the doors, then the doors might not open or might open and then close before the person has walked through them. To stop this from happening pressure pads are put down just before the door, so when someone steps on it this also causes the circuit to operate and for the doors to open, so there is always one device that will pick the person up. This is also good for safety, if there was just a P.I.R. and there was a fire, the smoke would block the infrared getting to the sensor, so the doors wouldnt open, but with pressure pads the doors would still be able to open. The doors operate in relation to change in infrared, or to pressure being exerted on the pressure pad. This is the circuit in which the P.I.R. and pressure mat work on: Power Source P.I.R. M P.M P.I.R. = Passive Infrared Detector P.M = Pressure Mat Logic Gates The circuit has an OR logic gate in it, this is where either of the two devices will make the doors open. INPUT OUTPUT P.I.R. P.M. Automatic Doors 0 0 Doesnt Open 0 1 Open 1 0 Open 1 1 Open This table shows that when one of the devices, P.I.R. or P.M. is activated that the automatic doors open. On the left half of the table a 1 represents the device being activated and the 0 represents it not being activated. So either one on its own, or both being activated will result in the doors opening. Photons In the crystal there are electrons, and photons are absorbed by the electrons, this is what gives the electrons the energy to move about, and therefore this is what sets up the voltage, and makes the current flow. Every single photon travels at the speed of light. The frequency of the radiation determines the amount of energy each photon has, the rule is the lower the frequency the lower the amount of energy the photon has, which also means, the higher the frequency the higher the amount of energy. How to work how much energy each photon has: I need to work out the frequency first: FREQUENCY = SPEED OF LIGHT / WAVELENGTH f = V / ? f = f = Now I can work out the energy: ENERGY (J) = Plancks constant (6.63 x 10?-34 Js) * FREQUENCY (Hz) E = h * f E = * E = Lenses The lens which is used is a FRESNEL LENS, it has been changed from a Plano convex, this is because it reduces the absorption by the lens. The Fresnel lens is a lens that is able to reduce the amount of material required compared to a normal Plano convex lens, it does this by breaking the lens into a set of concentric annular parts, and these are called Fresnel zones. 1 Fresnel lens 2 Plano Convex In the picture on the right you can see a Fresnel lens (1). You can see that in each of the Fresnel zones the, the overall width of the lens is lowered. This means that the original lens has been changed to a lens with the same curve but with discontinuities between it. This means that the overall thickness of the lens is greatly reduced, and therefore the weight and volume of the lens is also greatly decreased, but this is at the expense of reducing the imaging quality of the lens. I can work out the power that the lens has, for this I need the focal length. 0.65 = 0.01651m POWER = 1 / FOCAL LENGTH (m) POWER = 1 / 0.01651m POWER = 60.57 D Limitations If there is a power cut and the automatic door is a dual system with a pressure mat and detector, the pressure mat wouldnt work. If there is something wrong with the pressure mat then it involves digging it up which can cause hassle as is in the door way and will mean digging up concrete which will take time and be expensive. If there is a fire, smoke would cover the infrared detector and therefore the infrared rays that the person is giving off wouldnt be detected so the door wouldnt open and the person wouldnt be able to get out, and may die. That is only if it isnt a dual system without a pressure mat. Because the sensor is focused on the space leading up to the door it may be that if someone stands in the door way then the door will shut on them as there is no change in infrared radiation. When the P.I.R.s are used in security systems there are also flaws, which include a false alarm being raised if anything that isnt a human is detected, and therefore would set the alarm off when it is not needed. Other uses P.I.R. sensors can be used in many things, one of the main things is in security systems, as they are used to detect movement just as they are in the automatic doors, but instead of operating a system to let someone in when they are detected they are used to turn a light on when someone moves near it, or to set off an alarm or notify the police. P.I.R. systems have also been used in space; they have been used in a system which measures how much infrared radiation the sun and other planets are emitting. They are also used in toilets, for things like hand dryers, where a hand is placed underneath and then the infrared rays are detected and so the dryer starts to work, the same system is also used for taps in some places. Future Developments In the future the PIR sensor is hoped to be able to recognise individual people as everyone has a different infrared signature. These could be used in situations such as in a bank where only staff with a infrared frequency that has been registered are allowed into the back room with access to certain information, or in hospitals, only the correct staff will be let into the drugs cupboard. This could also work in football where any hooligans which have been banned from attending certain matches at certain grounds will have there infrared frequency registered with the system so the doors will not open for them. Also in development is a system for when people cross the road, as drivers sometimes ignore pedestrian signs and pedestrians walk across the road without pressing the button. The system is that a P.I.R. will detect a person walking towards the road and will set off a warning such as a light or flashing sign for the driver to see, therefore making them aware of the fact that ther e is a pedestrian crossing the road which will enable them slow down or stop.