Project Logs

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• Need more power!

  Jakub Kaderka • 03/22/2017 at 11:36 • 0 comments

  After some time of using darkstar underground I came into conclusion the maximal light output is far from enough, especially when visiting big cave domes, etc. There's not many ways to increase output power on the board as the LED heat transfer through vias is far from perfect. The solution could be using cooper as base material for PCB, but that's an expensive solution. Also the driver efficiency is not very good, lots of energy is wasted on switching transistor and current measuring resistors.

  These were the reasons why I decided to make a new, improved version. The basic operating principle stays the same (hystersis driven buck convertor), but that's all. New version will be powered by attiny (and finally programmed in C, not assembly) and will be designed for 2 A / LED current. Together with thee new CREE XP-L2 LEDS, the light output should be at bat-roasting level :)

  Work in progress...
  

• Testing underground

  Jakub Kaderka • 10/29/2016 at 08:39 • 0 comments

  After few months since the last log, the headlamp visited several underground places, survived muddy caves, dark mines, old tunnels,... Maximum output is much more than enough for most of the time, higher option would be nice for photography and bigger halls. I'm designing darkstar Mk.II as my bachelor thesis, so stay tuned!

• Project is finished

  Jakub Kaderka • 07/14/2016 at 18:49 • 0 comments

  Finally the remaining components arrived and the headlamp assembly is completed now! It's time to do some real life testing in wet and unfriendly underground.

• Run time test

  Jakub Kaderka • 06/28/2016 at 07:29 • 0 comments

  Using two 18650 from old laptop battery, the headlamp is able to run on reasonable walking power (~150mA, body is completely cool) for 25 hours, then it went to emergency mode with 40mA consumption and worked for another 4 hours.

  The charger was able to charge 3896mAh into batteries after this test.

  Also, I measured the weight of the headlamp. The lamp itself weights only 80g! Battery box is 45g and the battery pack is 96g -> the whole project weights 221g.
  

  Last thing missing is head strap and the project is finished! (Or I could just simply drill some holes to my helmet and use the screws to hold the lamp on its place. But I use the helmet for both caving and climbing, unmounting and mounting the lamp everytime I do a different sport would be pretty annoying...)
  

• Lab measurements of output light power

  Jakub Kaderka • 06/21/2016 at 20:29 • 0 comments

  Thanks to Ing. Jaroslav Stepanek, I have measured the real light output on Brno University of Technology, Faculty of Electrical Engineering in integrating speher.

  The expected value based on datasheet and measured current on full power was about 600lm, because of decreased efficiency of LED when heated and looses in optics and plexiglass cover, the real output was slightly over 200lm.

  If you are interested in more details, check the github page!
  

• Testing underground

  Jakub Kaderka • 05/23/2016 at 11:43 • 0 comments

  Tested underground, it produces a way more light than needed, one LED at second power level (about 150mA) is enough to walk and look around in a bigger cave.

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