1. Taking a White LED Lamp Forward Stuart France

2. The 1998 version  24 Nichia 5mm white LEDs  Current controlled DC-DC step-up  Oldham or CEAG headpiece  Continuously variable brightness knob  or 2-position pilot-main setting  3 x NiMH 18650 battery in Petzl box  originally 6 volt Kirby kidney pack on lead

4. Has anything happened in the past 10 years?  Microprocessors costing 50p  Software seen as an asset not a risk  Battery technology advances  Powerful single die white LEDs  Lenses for the above  LED torches become consumer item

5. Updating the lamp spec  3 x 3W Cree modules run at 2W (from Tesco)  3 x P4 in triple lens dichroic unit also possible  Push-button on-off  Brightness knob  Current controlled step-up to about 10 volts  Microprocessor for:  Power on/off function  Battery voltage measurement  Battery state LED signalling  Green, green-red, red, flash main beam, force off, when:  100-50%, 49-20%, 20-10%, 10-0%, 0% left

6. CEAG caplamp shell  Totally waterproof  no charger keyway, no rotary switch  IP68 push button, IP68 brightness knob  IP68 metal cable gland, siliconed inside  Tall bezel for dichroic lamp modules  Black sleeve to stop scatter  Nitrile rubber o-ring

8. Li-ion battery pack  Two 18650 cells, nominal 8V 2.5AH  Off the shelf £20 charger from CPC  Metal battery box, ends sealed with PU  Over-current cut-out  Two pin connector  spare line socket acts as a blanking plug  Attaches with super-velcro to flat area cast on rear of helmet

9. Push Button  3-second push to power on or off  Bicolour LED in middle shows for 15 secs after power off to indicate battery level  visible in cave when reflected off a hand

10. Brightness knob  Gives 6-to-1 power ratio  Suits small and large passages

12. Software  PIC12F675-04I/P (DIL8 package)  Easily reworked for other battery types  Battery monitoring can be disabled by jumper which allows any battery <10 volts to be used in an emergency  It will then deep discharge a Li-ion pack, and ruin it, but extract all the energy