The burrlight picture book (and Specifications)

Photo 1 - switched on . . Photo 2 - switch operation . . Photo 3 - switch strip removed

Photo 4 - empty hat-mount . . Photo 5 - hat-mount lit . . Photo 6 - hat-mount unlit

All photographs, by the way, were taken with a highly-modified Kodak DVC325 webcam. You can dig the practical details out of the microscope section of this website. Turn right at the 'fork in the road'.


Specifications and description

The burrlight is a torch/flashlight using a high brightness white LED. The principal features are :-

Dimensions. Length 90 mm (3.5 inches). Diameter 35 mm.

Light weight. The burrlight weighs 45 grams, compared to the more normal weight of 100 grams for a full-spec LED torch.

Sealed construction. This torch may be operated underwater, and repeatedly switched on and off underwater. It is sealed at all times.

It floats. This feature is very handy in lakes, less useful in fast-flowing shallow streams.

Brightness. 5000 millicandelas on a new battery.

Long battery life. 200 hours to half brightness.

Cold resistance. The Lithium Thionyl Chloride cell used produces half brightness at minus 25 degrees Celsius, or considerably colder than most of us experience outdoors. At these temperatures you are likely to be on snow, where much less light is needed anyway. Normally for extended travel the burrlight fits on your hat, where your head warmth lifts the torch temperature considerably above ambient.

Impact resistance. The burrlight typically fails after being thrown 20 metres in the air, and impacting a stone-chip road surface, one hundred times. A number of causes finally put the light out. Internal damage to the AA cell itself can cut light output drastically, or make it irregular, and soldered wires can tear off after 100 drastic impacts. So far the switch mechanism has not been damaged by impact, and the test switch has survived 600 such impacts. For normal use, where all you are likely to do is drop your torch, it will not go out.

Reliability. All connections, including those to the switch and Lithium cell, are hand soldered. No electronics are used to maintain the light output at constant brightness, until it suddenly fails, so if the light comes on when you test it before leaving on your trip, it will come on when you need it. The switch is a sealed magnetically operated reed switch which you actuate from outside the torch body. The magnet actuator is very low strength, and will not shift a compass needle if the compass is more than 10 cm (4 inches) away from the torch.

Replacement. After 200 hours or so, which should be quite a few years, if you like throwing things away, you can discard the burrlight. If, not you can mail it back for battery replacement, or solder a new battery in yourself after reading the full instructions provided. This device is engineered to be repeatedly refurbished, and spare components (for example end caps) are available.