Saturday, March 2, 2019

5 Watt flashlight conversion for $5

It's not really for astronomy use but the flashlight goes into my travel duffel. A 5 watt LED star can be easily installed into this cheap diving flashlight and powered by 14500 LiPO cells at 7.4 Volt and 2400 mAh.

Mor details under the cut.

The new LED star (5W 6-7V 700mAh) re-soldered in place and gorilla-glued in the original aluminum housing (1). No housing or circuit mod required.
Four 14500 LiPO cells (2) replacing stock AA batteries after the voltage chain modification from 4 in sequence (6V) to 2 in sequence by two in parallel (7.2V), using the DIY adapter (5, 6, 8).
The adapter is made of two PCB blanks linked by thick enough wire (6) to draw 700mA.
The bottom blank (5) has a single contact plate with two solder bumps for better contact with the lower cells' pair negative terminals.
The top blank is two-sided. The bottom has a single plate for positive terminals contact, the top has two for the original LED PCB positive and negative contacts. These contacts are wired to appropriate single side contacts of PCB blanks.
To assemble, put the Wire end (5) into the flashlight housing and lower 14500 cells all negative terminals down. Fit over the top the piece (8) so the positive and negative contact plates are properly aligned, and the connecting wire goes between cells. Put over the LED circuit housing (1) and screw down tight the focuser assembly (4).
That's all.

  1. The bottom of the original LED housing PCB may be short-circuited by the new adapter PCB (8). So it is important to isolate it well. I'm using two pieces of neatly cut electrical tape for now, but a plastic disk with terminal windows is in order.
  2. The magnet in the reed (magnetic) switch no longer working. Either the new PCB is blocking the field too much, or the module is too much misaligned vertically. For now, the solution is to use an additional helper magnet (2) which need to be swiped above the switch (set to ON position). The original switch still works to hold it and to turn off. While looking for a solution, I'm considering it a feature as the flashlight is often turned on on itself riding in a loose bag.

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