P2 Semester Report Sample 1: Electronics
To fulfill the requirements of the national diploma in Electrical Engineering or Computer Systems, the student must successfully complete all academic requirements as well as the work integrated learning (P1 for 6 month and P2 for 6 month) component.
This sample 1 is for a student who has successfully completed P1 and is doing a P2 in Electronic Security Industry, but it can be used for any other electronic industry as well, this is just a template, the concept is the same.
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- Unit 1: Energy Sources
- Unit 2: Hardware Systems
- Unit 3: Protection
- Unit 4: Installation and Commissioning
- Unit 5: Data Communication Systems
- Unit 6: Telemetry
1. Energy Sources
Energy in the form of electrical energy is needed in any electronic equipment to function. Power is normally supplied by the main AC 220V line or batteries.
In all electronic equipment there is a power supply which steps down the 220V into a lower voltage needed by the equipment and converts it into direct current (DC). The power supply might have one constant output or a variable one or multiple output with different voltages.
In electronic security for access control, the power supplies used to power the access control panel and it always have to be backed up with battery in case the main fails, the battery takes over.
There are many ways to produce electricity. Electricity is mostly produced by coal fired power generators, nuclear power stations and hydroelectric power stations. In recent years development in the renewable energy have been important due mostly to pollution especially with coil. Among the promising one, there is Fuel cell power and solar panels.
1.1 Fuel Cell
A fuel cell is an electrochemical conversion device. It produces electricity from fuel (on the anode side) and an oxidant (on the cathode side), which react in the presence of an electrolyte.
The reactants flow into the cell, and the reaction products flow out of it, while the electrolyte remains within it. Fuel cells can operate virtually continuously as long as the necessary flows are maintained. Fuel cells are different from electrochemical cell batteries in that they consume reactant, which must be replenished, whereas batteries store electrical energy chemically in a closed system. Additionally, while the electrodes within a battery react and change as a battery is charged or discharged, a fuel cell’s electrodes are catalytic and relatively stable.
Many combinations of fuel and oxidant are possible.
A hydrogen cell uses hydrogen as fuel and oxygen (usually from air) as oxidant. Other fuels include hydrocarbons and alcohols. Other oxidants include air, chlorine and chlorine dioxide.
1.1.1 Fuel Cell Design
A fuel cell works by catalysis, separating the component electrons and protons of the reactant fuel, and forcing the electrons to travel though a circuit, hence converting them to electrical power. The catalyst typically comprises a platinum group metal or alloy. Another catalytic process takes the electrons back in, combining them with the protons and the oxidant to form waste products (typically simple compounds like water and carbon dioxide).
1.1.2 Fuel Cell Efficiency
The efficiency of a fuel cell is dependent on the amount of power drawn from it. Drawing more power means drawing more current, this increases the losses in the fuel cell. Most losses manifest themselves as a voltage drop in the cell, so the efficiency of a cell is almost proportional to its voltage. For a fuel cell operated on air (rather than bottled oxygen), losses due to the air supply system must also be taken into account. This refers to the pressurization of the air and dehumidifying it. This reduces the efficiency significantly and brings it near to that of a compression ignition engine. Furthermore fuel cell efficiency decreases as load increases.
1.1.3 Fuel Cell Applications
A fuel cell system running on hydrogen can be compact and lightweight, and have no major moving parts. Fuel cells are used in electric and hybrid vehicles and auxiliary power ,notebook computers for applications where AC charging may not be available for weeks at a time, portable charging docks for small electronics (e.g. a belt clip that charges your cell phone or PDA) and Smartphone with high power consumption due to large displays and additional features like GPS might be equipped with micro fuel cells.
1.2 Solar Energy
Solar energy refers to the utilization of the radiant energy from the Sun and converting them into electricity or any other useful application (heating…).
Figure 1.1: A Solar panel
A solar cell, or photovoltaic cell (PV), is a device that converts light into direct current using the photoelectric effect. When grouped together in a panel array, they are called solar panel. Solar panels are mainly used to charge batteries for back-up power for home use (mainly in rural areas) or mostly in satellites.
A combination of solar panels, storage elements (Batteries) and inverters is widely used as a system for uninterruptable power supply (UPS), where the system is used to supply power in case of a failure in the main power supply. The solar panel charges the battery, which in turn supplies energy to the system after having been converted to AC current by the inverter.
2. Hardware systems
2.1. CCTV Camera
Close Circuit TV (CCTV) camera is a technology used in electronic security to monitor and or record certain areas of interest. CCTV is widely used in today developed world due to high rise in criminality and terrorism.
CCTV can be used for domestic purposes, having some few cameras monitoring the entrance of one’s gate, the contour of the wall and some other few areas of interest. However in industry, like big stores, banks or national buildings like airports, CCTV is more complex.
2.1.1 The Elements of CCTV
The Digital Video recorder (DVR), a Digital Video Recorder (DVR) is the central part of any CCTV system.
It works like a personal computer. A DVR has got hard drives to save data and operating software for the DVR which gives a DVR features like: MPEG4 data compression to save disc space, motion detection technology ( record only or send an alarm signal once a motion has been detected), Zooming ,event recording or play back and so on depending on each DVR. Some DVR includes a CD-RW to write back-up video footage on a CD.
When a CD-RW is not incorporate, most DVR got a USB port for external CD-RW or even for external hard drive if needed.
The cables from every camera are connected to the DVR depending on the number of channels it got. A 16 channel DVR can only connect 16 cameras. The screen is connected on the output of the DVR.
Figure 2.2: a DVR
The Cameras: a camera is the eye of the system. The camera converts the optical image into an electric signal. There are two main types of cameras: monochrome and color cameras.
In these two main types, there are also day and night cameras (which can view in day light and automatically adjust itself to view during the night), infrared cameras (which can see properly during the night because illuminated by an invisible infrared light), IP/TCP camera which has got a unique IP address and can be connected on a network switch and a PTZ camera also called high speed dome camera which can rotate, zoom and view a wide surface area.
Figure 2.3: A Camera
The Cables: a coaxial cable, industry standard RG59 is used to connect various analog devices of CCTV together. Sometimes an RG59 powerX (RG59 incorporating two core for power) is used to avoid pulling further cables for power of the cameras. When IP cameras are used, a network cable (CAT5 or CAT6) is used instead of RG59M
Monitor: a monitor for viewing the video footage can be either a monochrome or color screen. A normal cable (RG 59 cable with BNC connector) can be used to connect the screen to the DVR or a computer VGA cable can be used depending on the available connections on the DVR.
2.2. Access Control
Access control system controls and monitor access to buildings. Instead of the normal key, the door can only be opened when a valid card, tags is approached to the reader or by entering a pin code or if a registered fingerprint is read. Using cards has many advantages compare to using a conventional key. If a Tag or a card is lost, it can be voided from the system, and there is no need to change door locks. For added security, the system can be programmed so that a personal identification number (PIN) is also required before access is allowed or even finger print.
The movement of people entering and leaving the building can be monitored and stored for further analysis. Access can also be permitted to some people only at a certain period of time or in certain areas only.
The system can be configured to automatically trigger other systems (switching on the lights, activating CCTV camera…) when someone enters in the building.
2.2.1 The Elements of Access Control
The Controller: a controller is the main component in an access control. It connects to the PC and receives the program of the system. The controller stores all the settings of the system including the date and time, anti-pass-back status, all the tags or cards which are active in the system. The controller communicates with the rest of the system trough a bus link.
Fig 2.4: A Proxnet Controller
Push Buttons: When a button is pressed, usually a normally open push button, access is allowed. A push button is usually used to open a door from inside.
Card Readers: When a valid card or a tag is approached to the card reader access is allowed. A card reader connects to the controller via a bus cable. It reads the tag or card and sends the information to the controller for decision. Some access control system like Proxnet uses reader which have relays inside, the reader has a memory to store the cards which are supposed to open that reader and at the output of its relay, a magnetic lock is connected. When a card is badged, the reader makes the necessary decision to open the door or not, the controller is used only during the programming phase
Fig 2.5: A Proxnet Card Reader
Finger Print Reader: When someone whose finger print is in the system database is read by the finger print reader, access is allowed. Fingerprint readers usually use a separate bus cable and connect directly to the computer. The computer is used to enroll fingers in the system, but the fingerprint templates are usually stored inside the fingerprint.
Keypad: When a valid code is entered using the key pad, access is allowed.
Door Contacts: A small magnetic switch can be mounted on a door to monitor its status. Once the door opens, the switch sends a signal to the controller. Door contacts are usually mounted on fire exit doors or on doors which interlock with others (only one door can open at a time).
Magnetic Lock: An electromagnet is used with a soft metal plate to lock the door. When the power through the coil is cut, the plate releases the door. The magnetic lock is connected at the normally closed contacts of a relay so that there is a continuous power inside the lock.
Figure 2.6: Magnetic lock
Electric Motor: An electric motor can be used to close and open a gate. When activated, a motor will be triggered for a certain time closing or opening the gate. The motor is connected to the normally open contacts of a relay.
Electric Boom Gate: A boom gate is an arm gate. When activated, the motor inside lifts the arm up or pull it down depending on the previous action. Boom gates are usually used in entrance and exit of public parking.