USB chargeable flashlight

[Mitchell]

Hi

I know absolutely nothing about electronics but am going to try and make a small USB chargeable flashlight. Something like this
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I'm wondering if it is possible to do this without having an external charger and plug it directly into a USB port to make it more compact and practical. I'm assuming there's a reason this guy didn't do this in the first place but if it isn't a terrible idea how would I do it? Do I just need a different battery? Would I have to make it bigger? Any help would be appreciated and again please excuse me as I know nothing about electronics, thanks.

 

[kellys_eye]

Depends on what he's using as the charging voltage really. Since a USB port can only deliver 5V then if he included two cells that were wired in series and added up to greater than 5V then you'd have to include some form of boost converter to get the correct charging voltage.

There are many lithium charging circuits that can use the USB port voltage/current to charge cells and multiples of cells so actually doing it isn't a problem.

If you adopt the KISS principle then even a very simple resistive limiter charging circuit could be attached to a small ni-cad that powers the LED and, yes, connected directly to the USB plug.

Such portable lights already exist though... you are re-inventing the wheel. As an exercise in possibilities and building skills then fine, do what it takes!