Coolcaringer Engineering - Two Watt LED Caving Lamps

Coolcaringer Engineering - Two Watt LED Caving Lamps.

The 2 Watt Lamps use 5mm LEDs as their light source. These are Ultra/Hyper (or whatever adjective you wish to put in front of bright to make it sound brighter!) bright devices of a claimed 50,000 milli Candelas luminous intensity. These are fitted (presently) to a recycled Youle single bulb caplamp, cut down to about half its original size. The 5mm LEDs have integral beam forming characteristics and these form a beam of about 20 degrees.

This lamp uses a a resistive current regulator in series with each LED to balance the currents between the 24 LEDs. The LEDs, run at 25mA consume 24 x 25mA = 600mA which at 3.7v is 2.22 Watts. This produces a very bright light but draws a considerable current. To counter this, the 2 Watt lamp uses a "pulse width modulated" supply operating at about 800 Hz. Variation of the on-to-off ratio by a rotary control on the side of the headset (where the original switch used to be) controls the brightness from 2% to 98% of the maximum. This results in a linear reduction of current as the lamp is dimmed. Using the lamp at a lower setting in smaller passages and increasing to maximum at times when this is required allows the battery duration be increased over that which might be obtained were the lamp run at the full two Watts continuously.
Shown here on the right are two 2 Watt lamps with views from the front and back.

Update - November 2007 - These lamps have proved popular but I've now run out of Youle casings (I guess there must be more around as there were many made unless they're now all in landfill). To overcome the problem and, to some extent address the waterproofing issue, I've developed a single button controller (using a small microcontroller) that will allow the 2W lamp to be used with the more popular Oldham headlamp shell. The new lamp has variable output but, unlike the original continuously variable output, the new lamp will have stepped levels of (at present) Off, 10%, 50% and 100% brightness allowing the lamp to be backed off to 1W or about 200mW when the full power is not required. This will help with battery duration as before. I hope to have a prototype ready by the end of November so watch this space for details...

Update - January 2008 - The prototyping stage has been completed and these lamps are now available to order. The light output is PWM controlled as in the original 2W lamp with variable output but in this lamp a microcontroller does the hard work. A single 'tactile' push button, fitted into the original rotary switch position and covered with a waterproof rummer membrane, controls the light output via long or short pushes. The light level steps up or down accordingly. At present there are 6 light levels - Off, 10%, 25%, 50%, 75% and 100%. Energy drain from the battery increases or decreases in sympathy with the light level. I've also got a software modification that reduces the number of levels to 4 - Off, 10%, 50% and 100% - please state which you require.
The lamp starts in 50% mode when the battery is connected allowing the lamp to operate should the switch be damaged while underground. A further 'emergency measure' is incorporated where the internal electronic can be bypassed by removing the front of the lamp and changing the position of a jumper. This can be implemented should a catastrophic failure of the lamp's electronics occur.
The 2W microcontroller lamp operates from the same Li-Ion or NiMH batteries as the other Coolcaringer lamps.