LED Stairway Safety Night-Light

My elderly mother-in-law has had a few nasty falls on her stairs and landing over the last few months. A little investigation revealed that she had been walking around in the dark rather than turning on the ceiling light to save on electricity and because it was too bright at night. It appeared that an existing small plug-in night-light on the landing was not providing sufficient illumination to prevent trips and falls.

There were many possible solutions, but I wanted to make it simple, reliable, cheap to run, and not susceptible to being turned off 'to save electricity.' I had previously tried using discrete white 0.2" LEDs and a capacitive dropper / bridge rectifier / electrolytic capacitor as a bathroom night-light, but the LEDs were not really bright enough, and failed after only a few months, despite being run well within their data-sheeet ratings. However, it did show that the dimming circuit could be successfully housed within the ceiling pull-switch. (See image.)

Tests on some of the latest dimmable 230V LED GLS-type lamps revealed that they would work down to an appropriately low level with the addition of a simple mains voltage capacitor in series with the lamp. (A series resistor was included to limit surge current, improve reliability, and act as a fuse.) I tried that scheme in our bathroom, again mounting the components inside the ceiling pull-switch. Result - an excellent night-light, with full brightness available at the pull of a cord, which has now worked perfectly 24/7 for months.

This left the problem of where to mount the capacitor in the two-way wall-mounted switch circuit at the in-laws? Well, I don't know about the rest of the world, but a lot of UK lighting circuits use a combined mechanical mounting base, electrical junction box, and lampholder, called a ceiling rose and pendant. The ceiling rose includes terminals for switched live, permanent live, neutral, and earth. (Also sometimes marked as Line, Loop, Neutral, and earth.) Connecting the capacitor between the permanent live and switched live terminals inside the existing ceiling rose gave ideal night-time illumination, with full-brightness available at any time using the usual two-way switches at the top and bottom of the stairs.

The value of the capacitor will depend on the actual make and wattage of the lamp used, but I found that a 0.1uF 275V AC part with a 100R 1/4W series resistor worked perfectly with the 9.5W LED (100W tungsten-filament-equivalent) dimmable lamp I used. (For reliability, the capacitor must be at least X2-type 250V AC rated. However, should the component fail short-circuit, the worst consequence would be that the lamp comes on permanently at full brightness.)

On full brightness, consumption with this lamp is, of course, 9.5W, but when dimmed with the capacitor this reduces to only 4VA, with a Power Factor of about 0.5, so just 2 'real' Watts. That's about 500 hours per kWh, or about 1p per day to run at current prices.

I'm sure there are many other applications where a two-level light would be useful, and would love to hear your ideas. The best news is that, since installation, there have been no more little accidents, in either location.......

Just-in-case anyone reading this doesn't realise, this Instructable involves working with mains-voltage household wiring. Please ensure that the circuit is completely isolated at the fusebox / consumer unit / circuit breaker panel before making any modifications to the circuit. Also, always turn the lighting circuit off at source when changing the bulb at any time. In 'dim' mode, the current is limited to a few milliAmps by the series capacitor, but is still enough to give an uncomfortable electric shock if unwary fingers get into the lampholder.