Micro Rechargeable Flashlight





Introduction: Micro Rechargeable Flashlight

A simple rechargeable flashlight

How to make:

1. Take an LED and connect a switch to its positive side.
2. Connect the switch's other side to the positive of the super-capacitor
3. Connect the LED's negative to the positive end of the super-capacitor
4. Hot glue the  connections of the super-capacitor
5. Add more wire to the super-capacitor and fold it up the sides.

1. Make foil contacts (link).
2. Make pads curve and glue them to cardboard so the flashlight fits into them.
3. Apply power from wall wart.

Digital copy: https://www.instructables.com/file/FW82JWCG825HXY4/
Note: Open the digital copy with Fritzing (http://fritzing.org/).



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19 Discussions

Your explanation for construction is incorrect. You say to connect the negative end of the led to the positive end of the super capacitor, but you also say to connect the positive end of the super capacitor to the positive end of the led(through the switch). This would never word.

The smallest LED I have been able to find is the type that back lights a cell phone face, they are smaller than a pin head, I tried making the "worlds smallest flashlight" about a year ago and got sick of the leds getting lost and the terrible problems trying to solder them.

The 5 mm led is in a home made head frim a knurled fastner, the lens is from an LSU

mini leds 001.JPG

I find the idea interesting but a few questions...

with what do you charge the capacitor?

how long should it be charged?

how long does the light last?


short and simple... anyone needing a schematic needs to skip anything this complex.

and they wonder why I haven't posted any more instructables lately...

I can't help but agree with this. An instructable "instructs", it doesn't just "show".

However, if you would additionally post instructions, this would be very interesting to read! :)

6 replies

I'm going to keep an eye out for your next article on this - it looks interesting so it'll be good to see the details. 

you should have pictures of each of the building stages and a schematic, not just pics of the finished product

I did not photograph the build and do not have the parts to replicate it.
However i do have a digital copy.

Ok, and the current limiting resistor is where again? High power LED or not, excessive current firstly, kills any chance of having usable light for usable time, and second, will instantly degrade, or kill any LED regardless of how "high power" it is if the junction temperature exceeds max rating for ANY amount of time.

For the record, I am an EE and design circuits which are reliable for long periods of time using proper design principles.

This is not an instructable. It's an experiment from someone with little electronic knowledge. Not trying to be mean, but connecting an LED w/o current limit then justifying it by saying "I used a high power LED" just showcases the ignorance. The author's curt, non-replies further highlight this point.

What you have here is a slow-speed flash of sorts. Really bright for an instant, then with no charge left, a declining dimming light source.

This also exceeds the current ratings and probably the voltage rating of the supercap as there is no voltage regulation used. Also damaging and potentially explosive.


This I suppose should be flagged as unacceptable as personally I strongly advise nobody to build this and expect much from it. If you have trash parts to play with, then go ahead and play. But "rechargeable flashlight" this isn't!

Adding current (LED and Supercap charge) and voltage limiting (Supercap charge) will easily and cheaply add a lot of potential.

capacitor max rating: 5v
led rating: 4.5v
psu rating: 4.5v

Also, this is meant to be TINY not EFFICIENT.

And NOWHERE have you mentioned the critical parts omitted: current and power ratings.

Voltage alone means squat here ESPECIALY when dealing with non-linear semiconductors like LEDs which JFYI, have a NEGATIVE TC. It's assumed that's foreign to you but is really one more major nail in this experiment. It's called positive feedback and VERY few cases, and I've used PF in exactly VERY FEW CASES, is a very powerful technique. Passing totaly unregulated current through diodes, limited strictly by loop resistances does not qualify by any means, "regulated" and not even "limited" an any sort of sense which will ensure any form of lifespan of the devices.

Your max ratings while "within limits" take nothing else into consideration and as such, are meaningless by themselves.

"Tiny not efficient" in this case boils down to tiny, inefficient, and deadly for the components used. I'll give you the first two.

Bottom line: You get an A for experimental effort, which many of us begin with. But sorry, you get an F for publishing it as a misleading project which, if you read the comments, many other people would love to build based soley upon your (sorry) uneducated claims.

The good thing is that nothing here is dangerous enough to really cause harm, except perhaps to one's cash...

Again, not trying to be mean. But electronics relies ona lot more than "well the voltage is less than the max so it's OK to do". Hardly. Three fundamnetal design quantities: voltage, current, and perhaps most importantly, power dissipation. Cover those, and you'll be way ahead.

Have fun, be safe.

 I love this small flash light. Keep the good work!