OSH Park
12.5mm driver and XP LED V1.2
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12.5mm driver and XP LED V1.2
by
DavidEF.
2
layer board of
0.52x0.52
inches
(13.28x13.28
mm).
Shared on
January 20th, 2017 22:34.
I made this driver to fit in a tiny zoomable keychain flashlight I found at Lowe’s Home Improvement. The flashlight currently contains a cheap LED on a PCB, and no driver. It uses 4 button cells to power the LED directly. There is a clicky switch in the tail of the flashlight. It’s the smallest zoomable I’ve ever seen, and probably the smallest flashlight I’ve ever seen with a clicky switch. Since there is no driver, with a single PCB containing only the LED, I decided to make this driver board with all the driver components on one side and the LED pads on the other side so that it would be a drop-in solution.
The exposed copper rim on the driver side is the Batt- and/or Ground connection for the driver. The extra exposed copper between R1 and the reverse polarity protection diode is the connection for Batt+ and/or LED+ input to the driver and also connects directly to the positive side of the LED. There is another pad marked L+ which is not connected to anything. I put it there so that a wire or other small piece of copper can be soldered to the actual Batt+ / LED+ pad (between R1 and the diode) and to the L+ pad, making a bridge across the board, which will contact the top of the battery when installed in the light. Great care must be taken to not short that wire to the ground ring, any of the components, or the grounded shell of the flashlight.
This driver is made to be small, but still have regulated output. OSH Park requires a 15mil distance to the dimensional outline to be free of copper so I padded the board by that much around the edge. If you sand down to the edge of the copper pour, this board will be 12.5mm diameter. That is the diameter I need for the flashlight that I have in mind for this board. Sand even further, and you should be able to get it down to 11mm diameter for smaller lights. If you do that, you will have to get creative with grounding the driver. This driver requires the 10 pin Atmel Tiny13a MMU chip. The LED footprint is made for any CREE XP emitter and other LEDs with compatible footprint.
*Updated to add more vias for better electrical and thermal conductivity.