Introduction: Supercapacitor USB Flashlight
Like I'm sure most Instructable users I have a jun...err..future projects box and to find things in said box can be quite a challenge...
I needed a small flashlight that doesn't always need new batteries or needs hours to charge....and needs to be very rugged.
Supercapacitors to the rescue, with my current setup it plugs into a USB for less than 1 minute to a full charge for about 30 minutes of runtime.
For my build I used:
4 Starcap 2.7V 5F capacitors
Male USB connector
2 Resistors 1ohm & 100ohm
1 Ultra high efficiency CREE 5mm White LED
1 Mercury switch
....Not necessary but I also etched a small PCB to hold the components.
Step 1: Keep It Together
I decided to make a small PCB on my CNC.
I start with a quick design on EasyEDA exported as a black and white image.
Then I take a photoresist copper board and engrave the image onto the board with my CNC equipped with a 3500mw 405NM laser. You don't need a lot of power it only takes about 50mw of power to expose the board. As you can see I created some sunglasses for my laser to reduce light spill from the laser module.
I run the engraving at about 500mm/min and at ~100mw power.
After that is finished I develop the board and etch it in a hydrogen peroxide and pool acid solution.
This is how I make all my PCB's and I'm very happy with the results.
Soldering the flashlight is easy:
USB goes through a resistor to limit the current to supercapacitors this protects your USB, I used a 1ohm resistor.
Two of the supercapacitors are first soldered in series to make a 5.4V 2.5F capacitor then in parallel so that we end up with a 5.4V 5F capacitor.
From the capacitors we have the mercury switch that turns the flashlight on when pointed downwards.
This goes to a 100ohm resistor and then to the LED.
USB->1ohm resistor->Supercapacitor->Mercury switch->100ohm resistor->LED
Step 2: Cover Up!
To hold everything I just 3D printed a simple enclosure out of ABS.
Step 3: Finish Line
Everything is then put in the enclosure and sealed up to make it waterproof and painted.
Plugged it in and within a few seconds I was ready to go for a rummage in my part box.
If you have any questions please leave a comment.
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