Our safety lighting is designed to allow people to navigate safely around the smart home at night when it is dark. It is typically used in rooms and spaces that people may visit at night but don't want to light up automatically, so they don't get dazzled by bright lights. It is a small part in providing a great user experience and in our home is a zero-touch user experience.
We define safety lighting as a low-level ambient lighting in places where it is needed. It is designed to provide just enough light to see by but not enough to keep people awake at night. We have implemented it this way to avoid people be dazzled by normal lighting when for example, they get up to go to the bathroom.
We have designed our safety lighting to be almost invisible when not in use and have configured it to only come on when it is dark outside (as determined by our twilight sensor). It provides just enough light to see by and helps negotiate hazards such as stairs, corridors and doorways. It is also designed to only come on when our home is occupied.
Safety lighting is much more easily installed in a new build. Typically, it would all be one single logical lighting circuit but distributed around the home. We have used 12V dc power and a pair of 16/0.20mm 0.5mm² 11amp 'thinwall', automotive grade cables to connect it all up. Because the currents involved are so low, there is negligible voltage drop along very long lengths of wire. Any voltage drops are also handled by the simple electronics involved.
Most of the actual light fixtures are 5mm warm white LEDs using a very cheap and reliable LM317 current regulator IC in a TO-92 package. For our safety lighting we run these LEDs at about 4mA. This ensures a fixed brightness level regardless of any variations in the supply voltage.
This type of installation is very energy efficient and allows us to power it via our 12V Uninterruptible Power Supply (UPS). Each instance (wiring aside) costs about 30p in components.
Safety lighting is something that everyone should consider in a new build in our view (along with emergency lighting. If done during the build it will be very cheap to install and is a very useful feature of the smart home. Whilst it is harder to retro-fit into an existing home is can be done fairly easily because of the very low voltages and current involved.
