P2 Semester Report Sample 1: Electronics Page 2
Protection is very important in any electronic system. Huge damages in equipment can occur in an unprotected system. CCTV System installations and Access control are vulnerable to lightning induced surge, static and other interference, particularly on long cable runs and also when system transverse between buildings.
Severe damage can occur to cameras, recorders, monitors, controllers, readers and other peripheral equipment that are not adequately protected. Lightning surge protectors are high energy surge arrestors used to limit hazardous energy to safe levels. For ultimate protection always install protectors on each side of the cable.
In access control, the bus cable used must always be a shielded cable especially if is a long run. The shield of the cable must be connected on ground at one end point only. If connected at both end points, ground-loop currents can be built up in the system which can create more problems. Arc suppression circuitry must be fitted on all doors where there are strike locks or magnetic locks.
Power supplies used in the system should be of good standard and should fulfill these requirements:
- The power supply must provide the correct voltage and be capable of supplying the required current
- It is required to adequately ground/earth the system units to a good mains ground. This can be done by connecting a ground lead to the negative (-) terminal of the power input.
- All mains supplies to the power supply should be protected from high surge voltages by means of Metal Oxide Varistors (MOV), line transformers, or UPS (Un-interruptible Power Supply) systems.
- Power supplies with battery backup are preferable, to ensure that frequent occurrences of mains ‘brown-outs’ have no effect on the Reader/Controller performance.
- Ideally ONE power supply should be installed for the set of Readers and Terminals associated with each door.
- Ideally each high current magnetic lock should be powered from a separate supply
- It is important that the input voltage to any unit supplied by the PSU should not exceed the value specified in the installation manual for that unit, as damage to the unit may result.
- Power connection to the units requires conductors with a minimum cross sectional area of 0.5 mm² (0.0008 in²). (i) When units in separate buildings are connected and the earth/ground potentials are different, then a fiber-optic link between the two buildings is necessary.
4. Installation and Commissioning
The installation of CCTV camera system requires the study of the area to be protected to determine which are the areas of great concerns where cameras should be installed.
A secure place to be a control room where the screens should be mounted and also a secure place where the DVR will be placed. The cable used for installation is RG 59 or RG 59 power X if normal cameras are used.
If IP/TCP cameras are used, a network (CAT 5) cable has to be used. When RG59 cables are used, BNC connectors have to be crimped on both end of the cable to enable connection to the camera and the DVR. When CAT5 cable is used, RJ45 connectors are used
Figure 4.3: The overview of CCTV camera connection
A maximum of 16 cameras may be connected directly on most of the video in inputs of this DVR.
Depending on the type of monitor used which can be connected at either video out VGA, video out composite or s-video. An optional Audio input if sound is required and an optional Audio out may also be used. The LAN output is reserved for network connection in case there is a need to view the content of the DVR over the network. The RS 485/alarm output is used when a PTZ camera is used it needs command data about rotating left or right or zooming in or out at a specific target. Commissioning a CCTV system is about setting the DVR. Naming the cameras on the screen for easy identification, setting the network IP/TCP address and setting the type of record mode (with motion detector, generating alarms…)
4.2 Access Control
Access control is widely used in industry and commercial buildings.
Before the installation, a study of the building, the environment and the number of people who will use the facilities has to be determined in order to know which access control system is best suitable. There are many access control systems in the market ranging from single door only to ones which can supports hundred of doors with thousand of cards registered in the system. Some are more suitable in corporate office buildings because of the flexibility and their design while some are more suitable in mining because of their robustness.
Figure 4.4: Connection of Proxnet Controller to PC and to the rest of the network
The figure 4.4 above shows how a Proxnet controller is connected to the system. An RS-232 bus connects the controller to the PC. The out bus from the controller goes to the rest of the network from reader to reader and ends at the last device where a line terminating resistor is inserted. From each device to the next, polarity of the bus cable must always be respected
Commissioning the system require installation of Proxnet software in the computer, configuring all the parameters, creating all the areas, access level, time zones, create all readers in the system and putting all the cards with the details of their bearers in the system. Once this is done, the information is send to the controller which in turn sends to all the readers
5. Data Communication Systems
In every electronic installation, there are different ways components of a system communicate with each other. Data in electronic is simply electrical signals generated from a controlling unit to the controlled devices to operate, activate or calibrate them.
Data can also come from the controlled devices to the controller to inform the controller about their status or acquire input information. Bus is a term generally used in electronic to refer to data communication channel or path.
5.1 Bus System in Access Control
Access control system controls and monitor access to buildings. The system is generally comprised with a controller, a PC and door units which can be card readers, fingerprint readers, keypads, magnetic locks or strikers. All these equipment have to communicate with the controller through a bus system.
Figure 5.1: An Impro Access control system showing the different buses.
There are two data bus types used in access control: A host bus and the terminal bus
5.1.1 Host Bus
The connection from the host computer to the access controller is the host Bus.
The industry standard is either through a Recommended Standard 232(RS-232) also known as DB9 connector or RS-485. Mostly the RS-232 is used as a host bus for serial data communication between the PC and the controller. The maximum distance from the computer to the controller is limited to 25 meters but practically to avoid losing data and interference, this distance is kept to maximum of 15 meters. If longer distance is needed, an RS-232 to RS-485 converter can be used to increase the distance up to 1000 meters.
Today, RS-232 port is gradually being superseded in personal computers by a USB for local communications. Compared with RS-232, USB is faster, has lower voltage levels, and has connectors that are simpler to connect and use. USB is designed to make it easy for device drivers to communicate with hardware. However, there is no direct analog to the terminal programs used to let users to communicate directly with serial ports.
USB is more complex than the RS-232 standard because it includes a protocol for transferring data to devices. This requires more software to support the protocol used The RS-232 cable can be comprised of 3 or 5 wires.
If 3 wires are used, which is mostly the case, Transmit (Tx), Receive (Rx) and Ground are used. If 5 wires are used, other wires are used for data request and verification. The baud rate of data has to be set properly on the PC com menu to ensure correct and faster transfer of data.
5.1.2 Terminal Bus
The terminal Bus is the bus that links the controller to other devices in the system. The industry standard is through RS-485 which is made of a twisted pair of shielded cable.
The maximum distance is 1000 meters. If more distance is needed, a repeater has to be used. When wiring the devices, the shied of the bus cable has to be connected to ground to avoid interference in build up noise in the system especially when the bus is too long.
The standard color for bus wires is Yellow for positive and green for negative. Polarity has to be always respected through all the devices on the network.
The bus wire must always be routed separately from power cables to avoid interference and noise. For a system where the computer is not located in the same place as the rest of the installation, the computer can be connected to an Ethernet adapter with an RS-232 cable to the internet network. From the other location where the rest of the system is located, the system is connected to the internet through an Ethernet TCP/IP interface.
Telemetry is a technology that allows the remote monitoring, measurement, activation, calibration and reporting of information of interest to the operator.
Systems that need instructions and data sent to them in order to operate require telemetry technology to be in place. Telemetry can be wireless, or can use cables, computer network (Ethernet) via telephone line or optical fiber link. In CCTV (Closed Circuit TV) Camera systems, Telemetry is used to send video footage captured by different cameras to a remote control room.
Companies like banks which require high security and which normally have many branches usually use telemetry to send video data collected to different control rooms or individual cameras to a central main control room through telemetry to allow further analysis of the data, record keeping.
Figure 6.1 shows an Impro access control system using telemetry. The controller sends data through a modem to an Ethernet link where a remote computer can access data. People entering and living the building or any alarm generated in the system can be accessed through this remote computer. The settings of the system can be changed also with this computer.
In CCTV (Closed Circuit TV) Camera surveillance, Telemetry is widely used to report video footage captured by different cameras to a central remote control room especially in companies like banks which have usually many branches. The idea is to see what is happening at every branch and do not let the security officers at branches to temper with the security system. There are software on the market which permits to view the contents of a digital Video Recorder (DVR) remotely. Smart viewer is software that a general computer user can install in his PC to monitor and/or record the video and audio from a Samsung SHR-2160/2162/2080/2082 DVR in real time through network without going to the site where the DVR is.
Figure 6.2 A typical connection of a DVR to internet link.
The LAN (Local Area Network) port of the DVR is connected to a network switch with a cat 5 cable.
The network switch is in turn connected to internet. The user has to have internet connection and select the right IP/TCP address is his smart viewer (viewing) software to access the DVR.
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