12V DC Emergency Lighting

This project is based around the need for several types of lighting in our home. Emergency lighting is designed to come on in specific locations in our home when the alarm goes off and the home is occupied.


The emergency lighting power comes from our 12V battery bank, via the 12V monitoring module.


The emergency lighting power is controlled and switched by the Home Control System (HCS), which uses a Ethernet IO board to switch the power via a power transistor.


We have define a colour coding convention for wiring and ducting in our home. This approach makes the installation easier, much tidier and also means it could be removed very quickly from our home if required. It also ensures separation of low voltage wiring and keeps it away from the mains wiring in our home.

Automotive purple wire
Colour coded (purple) wiring is used to distribute the power to all of the emergency lights. Because it is readily available in 100m rolls, we have used a 16/0.20mm, 0.5mm², 11amp 'thinwall' cable. At some points, the distribution network will split into a 'star network' and this will be achieved using a 6-way blade terminal and insulated blade connectors.

A common earth is distributed from the the battery bank, through ducting and runs to each light. This reduces the amount of wiring required and this common earth then works regardless of the functions each light is used for. All earth (-ve battery terminal) wiring is done using thick, black wire.


It is envisaged that all of the emergency lighting is using very low power LEDs, to reduce the current and thus the voltage drop across the wiring. The total lighting load is planned to be less than 10W.


The 'Emergency Lighting' is an object modelled in our Home Control System (HCS) as a static Java class. It maintains state in a local database.


This project is currently live. The Home Control System (HCS) USB output board and power transistor sections are working. The remaining work is now further installation of the wiring and connecting up further lighting.


  • Whilst not a major feature of our home and not even one we plan to use, the emergency lighting is a worthwhile and useful feature. It is a cheap and simple thing to do.

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