OLDHAM CONVERSION TO 3W LED FOR ABOUT £25

This page is about how to convert a spare Oldham headset to a 3 Watt LED light

The LED was a seoul natural white 3.2W LED purchased from this web site

http://www.dotlight.de/shop/index.php/cPath/296_292  

 for a total cost of £11.80 (b4 the £ plumeted!) .Other items purchased were 2 * 3AA battery packs + clips from Maplins (£2.00 approx) and 2 packs of 2 amp hour  NIMh AA rechargeable batteries from Maplin (on special offer for £4.00 each pack)

Other items required :thermal contact paste or tape (availble from dotlight)

                                :small piece of 5mm metal sheet (preferably alloy as it is easier to cut )

Remove the 2 screws inside the headset that hold the contact bar in place and also the external screw that is the charging contact . Cut the metal plate to the rough shape as seen in the image  (sorry best my £15 Tesco digital camers will do!)so that it clears all other components but is as large as possible (to provide maximum cooling area) .Drill 2 holes for the screws to hold it in the place of the contact bar .Solder 2 wires to the tags on the LED printed circuit , put contact paste on the PC and fix it in a central position on the metal plate so it will shine through the reflector -fix in place with a couple drops of glue .Connect the + wire to the contact bar and the - to the tag going to the centre contact of the bulb (actually do this b4 you screw in the metal plate !).File down back of reflector (there are at least 2 types of these -one gives a more focused beam than the other) so that it will all fit together (experiment with this to get the beam you like).

Glue the 2 battery packs back to back and connect up wires with correct polarity with the 2 packs in parallel (NOT IN SERIES OR YOU WILL BURN OUT THE LED) and try out.Put battery pack in a suitable container (currently a chopped up plastic drinks bottle either for helmet mounting or to go in your suit top pocket.

The LED is max rated at 800 ma so theoretically it should go for 5 hours  with these batteries, however as the volts drop so does the current ,so in fact it gives a reasonable light for over 6 hours

note

The LED gets very hot at 800 ma (it must have a heat sink) and could burn out if it gets too hot  (it will  also scorch your fingers) so I`ve milled the edges of the heat sink and also tapped the external contact  screw back in to provide extra cooling (this heating  up of course means that these LED are not very efficient!).

If you use non rechargeables the voltage  @1.5V/cell will be over the design voltage so the LED will be overun initially and could burn out! You`ve been warned

PILOT LIGHT

You can have one by getting  a small white LED from Maplins for  (about £3.00) and soldering it into the base of the old pilot light and potting it in with a drop of epoxy.

OTHER.

Voltage control chips/circuits are available (whether they would fit in I don`t know ) which are theoretically better at maximising LED and battery light ) on the other hand they add complexity and expense and reduce reliability especially as these headsets aren`t renowned for their water resistence.

ALSO NEVER STARE AT THE LED AS IT IS POWERFUL ENOUGH TO DAMAGE YOUR EYES (PASSING GLIMPSES ARE OK)