Interference issue in CCTV due to Grounding

Interference issue in CCTV due to Grounding

Most of small size CCTV installation faces various type of interference issue. Most of Home, jewellery shop, grocery shop, youth hostel …… etc.

There are several factors that can cause interference problems in a security camera. Below is a list of some of them:

1. Use of improper power supply.
2. Use of poor quality cables
3. Use of poor quality cameras
4. Use of poor quality converters
5. Incorrect grounding
6. Camera Warm Up
7. Poor connections
​8. Lack of adequate lighting

In this article we understand Famous issue 5. Incorrect grounding.

If grounding is done improperly, you may see bands rolling on the screen, if this is the case, there is an interference problem called the ground loop.

This problem basically occurs when the camera, DVR or power source groundings are made at distinct points that have different resistances, this causes an effect called a ground loop.

To solve the ground loop problem simply ground the equipment to the same common point (ground bus) or leave one side (camera) without contact with the ground.

A practical example would be to place a wood, plastic or other insulation material on the back of the camera mounting bracket so that it does not come in direct contact with the post or wall that is installed.

Now only that if we rectify Earth & Neutral line of main voltage, the issue is rectified.

Neutral:

Neutral is the normal”return” wire.

In systems where the load is supplied from only one Hot (or “Live”) wire, the Neutral completes the circuit and carries current back from the load to the power station.

Neutral is a conductor that carries current in normal operation.

Neutral represents a reference point within an electrical distribution system.

Earth:

Earth or Ground wire is a safety protective wire for the human body and electrical equipment from fault conditions.

Earth is a conductor that carries no current in normal operation.

Earth is a conductor that carries current under fault conditions such as insulation breakdown that occurs within electrical equipment.

In a polyphase (usually three-phase) AC system, the neutral conductor is intended to have similar voltages to each of the other circuit conductors, but may carry very little current if the phases are balanced.

The United States' National Electrical Code and Canadian electrical code only define neutral as the grounded, not the polyphase common connection. In North American use, the polyphase definition is used in less formal language but not in official specifications. In the United Kingdom the Institution of Engineering and Technology defines a neutral conductor as one connected to the supply system neutral point, which includes both these uses.

As per Indian CEAR (Central Electricity Authority Regulations, CEAR came into effect 20 September 2010, in place of The Indian Electricity Rules, 1956.) neutral conductor means that conductor of a multi-wire system, the voltage of which is normally intermediate between the voltages of the other conductors of the system and shall also include return wire of the single phase system.

All neutral wires of the same earthed (grounded) electrical system should have the same electrical potential, because they are all connected through the system ground. Neutral conductors are usually insulated for the same voltage as the line conductors, with interesting exceptions.

Keep in mind The camera also requires a minimum current, which is usually less than 1A (ampere) for our example of a traditional CCTV camera.

The indication of the electrical current required for the camera to operate must be in the product manual, consult your distributor to be sure about the consumption of the camera, because in some cases with the use of infrared illumination the required current may be higher.

May this issue you face during final commissioning or after handover. Solutions remain same.

To know more visit http://arindamcctvaccesscontrol.blogspot.com/2014/01/ground-loop-problems-in-camera-output.html

Know about BMS technical protocols

BMS - What you should know about technical protocols

If you or a client is choosing a building management system (or BMS), it’s important to understand how it communicates information with digital devices such as controllers, meters, and input/output boards, and computers.

The details are important because some BMS use languages—or technical protocols—that lock you into using their vendor’s proprietary technology. Use of such protocols may force you and your client to pay higher prices for software and hardware available from only one vendor or its licensees.

This article describes common categories of BMS protocols. It recommends that you avoid proprietary protocols and favor more open ones.

A BMS communicates through protocols

To exchange data, digital devices must use a common data structure and a common channel or medium of communication.

The figure below shows a master BMS that communicates with devices that use microprocessors. They include a roof-top unit (or RTU), refrigeration controllers, energy meters, and other input/output boards within a building. The building controller also uses the Internet to share temperature, operating parameters, or energy data with remote users through enterprise servers or personal computers.

A BMS protocol defines the format and meaning of each data element, in much the same way a dictionary defines the spelling and meaning of words.

The data exchange often occurs through a physical wire such as a twisted-pair RS485 or an Ethernet CAT5 cable). It may also occur wirelessly over wi-fi network, through an internet protocol (or IP).

The phrase “BACNet over IP” means the BACNet protocol communicates through an IP network.

Some protocols are more open than others

Protocols fit in one of four categories, depending on their relative “openness:”

1.       Open. The protocol is readily available to everyone.

2.       Standard. All parties agree to a common data structure. The protocol may be an industry standard, such as BACnet and Modbus.

3.       Inter-operable. The protocol is vendor agnostic. A controller from one vendor can replace one from a different vendor.

4.       Proprietary. The data structure is restricted to the creator of the device.

Why you want BMS with open protocols

A BMS with proprietary protocols locks the system owner into using a single BMS vendor. For example, you can’t remotely change the set points of a proprietary BMS unless you use the vendor’s software.

In contrast, with open and standard BMS protocols you can shop for alternative providers of digital devices and enterprise software.

This is why use of proprietary protocols is inconsistent with best practice. The lesson is clear:

In choosing a BMS, be sure its protocols are not proprietary.

How to know whether a BMS protocol is open

To determine whether a BMS protocol is open, ask the vendor two simple questions:

1.       Can your competitors exchange data with your BMS?

2.   Is the system’s protocol published in such a way that it’s easily accessible to everyone (including competitors)?

Best open protocols: BACNet, Modbus, and XML

For a master controller that exchanges data with devices and meters within a building, prefer the BACNet, Modbus or any other standard protocol. Otherwise, make sure it’s at least open enough so anyone with proper security access can read and write information.

For remote enterprise access (protocol B in the figure), organizations often use BACnet over IP.

The current trend is toward use of additional Internet technologies. Companies like Honeywell Tridium (Niagara framework) and many others have exchanged data through standard internet eXtensible Markup Language (or XML) with web services.

Even the ASHRAE BACNet committee has convened a working group to define use of XML with BACnet systems. The group is also working to define web services that will enable data exchange between building automation and control systems and various enterprise management systems.

Put in short, use these criteria when you’re choosing devices and BMS:

·         For devices such as RTUs and refrigeration controllers, look for ones that use open protocols such as BACnet or Modbus.

·        Make sure these devices give you both “read” and “write” capabilities so you can change set points.

·         For easy enterprise access, choose a BMS with web services and XML capabilities.

·         Make sure the web services of the BMS allow both read and write capabilities.

·      Be sure the BMS supplier provides the XML dictionary and definitions of web services to anyone, including competitors.

 

This Artical published on April 2019 at Safe secure Magazine.