Introduction: Supercapacitor USB Light

Picture of Supercapacitor USB Light

For those who never heard about supercapacitor, you can check for more info about supercapacitor here. Supercapacitor is basically a capacitor with very high capacity, and the capacity rating is normally around few Farads. With the “super” capacity, it basically can store a lot of charge, and I am going to use the “super” capacity to store charges for a 5mm LED. Let’s see how long will the 5mm LED last.

Step 1: Components Needed

Picture of Components Needed

The components you will need for this project is basically a supercapacitor (I am using 5.5V 0.1F supercapacitor which I bought from Farnell), a White LED, a 1K Ohm resistor and a USB male connector (I get this from an broken pendrive).

Step 2: Supercapacitor Polarity

Picture of Supercapacitor Polarity

Make sure you know the polarity of the supercapacitor, or refer to its datasheet

Step 3: Soldering

Picture of Soldering

The first step is to cut the 2nd and 3rd pin of the USB male connector, we will need only the 1st and 4th pin (5V and 0V pin).

Then solder the negative pin of the supercapacitor to the 4th (0V) pin of the USB male connector.

Now, try to connect the positive pin of the supercapacitor to the 1st pin (5V). For the connection I am using a resistor leg.

Step 4: Soldering

Picture of Soldering

Next, connect the positive pin of the White LED to the 1st pin (5V) of the USB male connector.

Finally, connect a 1K resistor from the negative pin of White LED to the 4th pin (0V) of the USB male connector.

Step 5: Schematic

Picture of Schematic

Please check the diagram below for the complete schematic. You are actually free to use higher Farad supercapacitor, but voltage rating must be larger or equal to 5V, and you can have your creative way to connect all the components together.

Step 6: Testing

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Now, plug it to your computer for around 10-30 seconds to charge up the supercapacitor.

You should see the White LED turned on (if it doesn’t turned on, there are some mistake in the connection), then after 10-30 second, you can unplug it and you should have around 10 minutes of the LED light.


Step 7: Circuit Update

Picture of Circuit Update

Circuit Update (6 Oct 2010)

I made some changes to the circuit, adding another resistor to limit the current consumption from USB port, and an ON/OFF switch to control the white LED.

The circuitry is simple, when you plug it into PC, the USB port will start charging the Supercapacitor, and there is a 10Ohm resistor (R1) limiting the current from USB port to 5V/10Ohm = 500mA maximum, but the R1 will also slow down the charging time. For large capacitance Supercap, you might need to let it charge for around 1 to 2 minutes. At the LED side, the S1 will let you turn ON or OFF the LED, and the 1KOhm resistor (R2) is to limit the current for the LED. If you use smaller value for R2, like 330Ohm, it will increase the brightness of LED but will also reduce the operating time of the LED for one charge. By using larger value for R2, you will increase the operating time, but reducing the brightness. I found 1K to be the balance value for the brightness and operating time.
Talking about the brightness and the operating time balance, I created another circuit that let you choose 3 level of brightness.

Step 8: Circuit Update

Picture of Circuit Update

In this circuit, the charging and USB port part is still the same, but I add in S2 and R3 at the LED side. So, the S1 and R2 will still function like the previous one, that by switching on S1, you will get the 1KOhm resistor brightness. By adding S2 and R3, it means that if you switch on S2, you will get 330Ohm brightness, which is brighter than 1KOhm brightness, because the resistor that limiting the LED current is now smaller and higher current on the LED means higher brightness. I say you will have 3 level brightness, so, the third level brightness is by switching ON S1 and S2 at the same time.
When S1 and S2 is being switch ON, the R2 and R3 form a parallel pattern, and you need some calculation to get the total resistance for the White LED.

The total resistance from the parallel of R2 and R3:
1/R = 1/R2 + 1/R3
R = 1 / ( 1/R2 +1/R3 )
R = 248.12Ohm
So, the total resistance at the White LED if you turn ON both S1 and S2 is 248.12Ohm which is 3rd level of brightness for the White LED.
- 1st level (S1 ON) – 1KOhm Brightness
- 2nd level (S2 ON) – 330Ohm Brightness
- 3rd level (S1 and S2 ON) – 248.12Ohm Brightness



JeffersonZ4 made it! (author)2017-03-14

I gave it an enclosure! :D

It's using a 0.47F supercapacitor and works for 21-24 minutes at a time, but it slowly dims.

I also used a switch.

Tip: If you're doing it with an enclosure, FINISH THE CIRCUIT before you put it in the enclosure. I learnt it the hard way.

sciguyhale (author)2016-09-22

would a 0.1 farad capacitor work? It's the cheapest one- 20 for $4

remusfillis (author)2016-02-10

How long does the light stay on?

pablotbbt (author)2015-02-23

I use a capacitor of 10 volts ?

jgilbride (author)pablotbbt2016-01-22

According to step 5, yes.

CkloneS made it! (author)2015-11-05

I built this with a 1.5 F 5.5v super-capacitor, I am a little bit suspicious that the capacitor I used is just a relabeled 1 F capacitor (stupid generic no-brand china). But anyway, Instead of your 1K OHM resistor, I only needed 100 OHM for an LED with specifications of 3.2v 20mA with capacitor out voltage at 5 - 5.3v (Depending on usb charger output voltage). I recycled everything else but the soldering tin (of course) and the capacitor, everything else is from old electronics, even wires, GO GREEN! Also, my modifications is an on/off switch, and potted half of it in hot glue. Quite nice little torch. Thank you sincerely for the inspiration, even though mine doesn't look as pretty as your's.

pmshah (author)2015-10-28

Look up AliExpress. You can get up to 4 F capacitors at bargain prices, delivered free any where in the world.I have a bunch of old ball point pens with built in batteries and single led torch. These originally cost me like 5 ¢ each. Practically don't have to spend any money.

MarosP (author)2015-02-17

A white led would probably handle 5V (+- 0.5V), and would be nicely bright. If you don't want to risk it, still, 1K ohm resistor seems to be too much.

buckminsterfullerene (author)2010-10-16

I just made mine and it is so awesome!! I did add a modify it though, instead of using just one LED I used two, and used a slide switch to alternate between them.

Awesome! I wanted to incorporate something like this into a bracelet but didn't want to use a battery! Now I don't have to! Thank you a lot for making this!

Very nice! You can use "3 step slide switch" (not sure the exact name of the slide switch with 3 steps), and you can choose to ON LED1, ON LED2, or OFF both LEDs.

madmanmoe64 (author)bustatech2010-10-18

3 stage slide switches really hard to get a hold of, I've looked several times. Do you know anywhere good?

jacobrb95 (author)madmanmoe642014-04-07 has them but all I could find were ON-ON-ON, I didn't see any ON-ON-OFF switches there.

Just don't connect the third input and it's the same thing.

wow, they are cool!

could you show me how to make this, thanks :)

can have the circuit you made to have the design

dragon_shadow88 (author)2010-10-15

it would be great to put a couple of supercap in paralel to get a larger capaticance, and you forgot that if not healty for supercaps to charge them with unlimited current, the USB port has a limmited current to 500mA , and it would be great to add some PWM to circuit, it's more efficiant than a ressistor, besause the ressistor turns the unused energy to heat, so the NE555 SMD in C-mos used like PWM would be perfect for this project

PS, there are supercap that has a capaticanse of 7F but only 2V , add a hand generator to charge it and a 1,5V LED driver and ingoy your hand rechargeable flash light.

sorry for bad english, I'm from Serbia :)

I am from the US, and your English is better than most Americans'. Please do not apologize. :-)

I know of a company that makes 150F supercapacitors at 1.5-2vdc for use in industrial applications

I never heard that much of capacitance before. 150F supercapacitors, that's monster size... I wonder what kind of circuit will need that amount of capacitance.

resently maxwell tecnologies came out with a 3000F 2.7V Boost cap! :D it's now avalible on the consumer market the only place i know that sells these is electronics goldmine and mouser there very nice capacitors and thier about 20-30$ on avrage each but if you get lucky you can get them for 10$!!! oh an answer to your qestion, these high capacitence capacitors are used in green energy, energy storage, and well as hybird cars :D

thank you for your answer :)

beju0506 (author)2014-02-09

Hi! I wanted to say thank you for posting this! I merged this idea with another one I came across here to make something new:
Just wanted to say thanks again for the inspiration! :)

ryanmercer (author)2011-04-04

Emergency USB back-up lighting :) although always on.

majikplant420 (author)ryanmercer2012-07-22

just add a micro switch in between capacitor and led loollolol

mittu gat (author)2012-07-12

hi what if i use 1.0F Capacitor ,,, will i get longer pereiod of discharge and what is the difference?

progman32 (author)2010-10-07

Pretty cool idea! One possible issue for people duplicating this. Depending on how fast your supercapacitor can charge, you may end up overdrawing on your USB port if the capacitor is fully discharged. Won't hurt anything, but the port will shut off power to protect itself, thus not charging your light. You may want to include a low-value resistor (maybe 1-3 ohms) between the cap and VCC if you find your light won't charge at all or just blinks once when you plug it in.

htetkyawlwin (author)progman322011-09-25

Absolutely.. that much of capacitance will initially make nearly short circuit current,
damaging the USB port... this is a good idea to place a low ohm resistor to charge capacitor...

XOIIO (author)htetkyawlwin2012-03-22

Why not just throw a diode in to prevent discharge?

bustatech (author)progman322010-10-07

Ya, notice about that issue, and I actually update a new circuit at step 7 and step 8 with the charging resistor included.

physicsguy137 (author)2012-01-16

My version, based on your Instructable. The two 1-F, 5-V super caps are connected in series with a 10-Ohm resistor (behind the round PCB). The 330-Ohm, current-limiting resistor is attached directly to one of the LED legs. All this fits in a small Altoids tin.

Mvtnns (author)2011-09-25

2 Farads?!?!?

Isn't that more than twice than earth's capacitance?!

SinAmos (author)2011-09-24


TechKid67 (author)2011-09-24

So in theory, could you attach a few of this set-ups to a 5v solar panel but with a few adjustments: Switches on the lights so they just charge and aren't lighting when not in use. Also, can the supercaps. be over charged?
p.s. Im looking toward ideas for a handy emergency light source

keithyboyx (author)2011-06-12

hi, relative newbie here, but how would you suggest wiring 5x capacitors to the circuit. forgive me i am new. thanks

bustatech (author)keithyboyx2011-06-12

To use 5 capacitors, simply parallel them.

rocketman221 (author)2011-05-27

Nice. I want to make one with a pair of these.

account3r2 (author)2011-02-04

What voltage does the LED need to be?

billbillt (author)account3r22011-05-16

A white LED uses 3.0 VDC.

bustatech (author)account3r22011-02-04

The forward voltage for White LED is around 3V.

matchlighter (author)2011-04-23

This seems like it would be a pretty neat technology to use in an IR pen input. Do you know if Supercaps are sensitive to being charged for too long? Or do they just reach their maximum and let any excess pass through?

Caboose98 (author)2011-03-28

awesome! how much was teh capacitor? i want to make this in a little flash drive case.

robot1398 (author)2011-01-09

whats the need of knowing the polatiry

greenkush (author)robot13982011-03-21

if you dont connect it right the capacitor will short circuit make the capacitor hot and maybe make it explode.

loppy96 (author)2010-10-04

will you get shocked to sh%^ if you touch the capacitor leads or?

bustatech (author)loppy962010-10-04

Actually you will not get shocked no matter how you touch the capacitor. The voltage is only 5V, and it is save for your hand.

90mp11 (author)bustatech2010-10-05

you will however start to discharge the capacitor and it may shorten the time from plugged in to no more light.

Arx (author)90mp112010-10-07

not really. The amount of current that will flow through your skin at 5V is effectively zero.

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