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ELT - Emergency Light Testing System

(image to follow)

| overview | control panel | remote unit | mains interface |


The Automatic Emergency Light Test System has been designed to reduce the amount of man hours required to carry out the mandatory testing of emergency lights in public buildings. BS5266, the regulation covering the procedures requires that:

a) maintained unit lamps are checked daily
b) all units are tested for functionality every month
c) partial discharge tests are carried out every six months
d) full discharge tests are carried out on all units after three years and annually thereafter.
Carrying out these tests, although essential, is laborious and time consuming. The Automatic Emergency Light Testing System will do all these tests automatically, reporting any problems automatically and logging all test results.

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System Overview

The system consists of a main control panel plus one remote unit per luminaire. The remote units report back to the main panel using the mains wiring in the premises so no extra wiring is required.
The main panel can control up to 500 luminaires and each remote unit can be configured to be maintained or non-maintained, three hour or one hour type and the frequency of tests can also be set. In addition, restrictions on when testing may be carried out can be imposed with regard to a user specified time window, an input from a twilight sensor or an input from an alarm panel (so that luminaires will be tested when the alarm is set and the premises empty).

All activities are logged at the main panel and can be printed on the system printer either continuously or on user request. Thus a hard copy of when each unit was tested is always available together with log entries when either user or engineer modes are used.

The log has a 1000 entry capability and is battery backed. The system information (set-up details for both the overall system and for individual remote units) is stored in EEPROM which which is therefore preserved even if the battery fails.

An additional serial port is available which could be connected via a modem to a central station. Software for this port is available on request.

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Central Control Panel

The main control panel is housed in a painted steel case which contains the main controller circuit board with the printer module and the local mains interface board. the front panel is hinged and the main pcb with the two line by sixteen character LCD display is fitted to it together with the 16 character keypad.
The main control board provides all the 'engineering' and 'user' mode facilities to set the time and date, change passwords, add or delete remote units and various other system related functions on the remote units.

The mains interface board takes the bi-directional data from the main board and transmits it into the mains wiring - it has no intelligence on-board being purely a mains modem.

The printer module uses a plain dot matrix impact printer plus associated controller board. It can easily be removed from the front panel for ribbon replacement etc.

The real-time clock and the RAM (in which the log is maintained) are battery backed in case of mains failure, whilst the system configuration details are copied into non-volitile EEPROM which will survive even if the on-board battery fails.

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Remote Unit

The remote unit is housed in a small painted steel case and contains one pcb on which all components are mounted. Connections are made from the incoming mains and to the luminaire to be controlled and additional wiring carries the signals sensors in the luminaire for charge indicator and light level. The light level sensor is a light dependant resistor fitted into a 'Terry' clip which is clipped around the fluorescent tube in the luminaire. The charge indicator sensor is another light dependant resistor which is optically coupled to the luminaires charge indicator LED by fitting both into a a heat-shrink or rubber sleeve.
As communications are carried out via mains wiring no other data wiring is required between the remote units and the control panel.

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Mains Interface Unit

If required up to two additional mains interface units may be connected to the main control unit (using two-pair cable) so that a separate mains unit may be incorporated into the system. examples of such additional systems are a computer room containing luminaires that are powered using a UPS (uninterruptible power supply) where the neutral-earth loop is broken by the UPS equipment, or a remote building whose mains is supplied from a different main distribution transformer, which again would break the neutral-earth loop.
The two-pair cable for this link may be extended up to 1 kilometre.

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