## Step 8: 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

Source: http://www.bustatech.com/supercapacitor-usb-light/
<p>I gave it an enclosure! :D</p><p>It's using a 0.47F supercapacitor and works for 21-24 minutes at a time, but it slowly dims.</p><p>I also used a switch.</p><p>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.</p>
<p>would a 0.1 farad capacitor work? It's the cheapest one- 20 for \$4</p>
<p>How long does the light stay on? </p>
<p>I use a capacitor of 10 volts ?</p>
<p>According to step 5, yes.</p>
<p>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.</p>
<p>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 &cent; each. Practically don't have to spend any money.</p>
<p>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. </p>
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.
<p>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!</p>
Very nice! You can use &quot;3 step slide switch&quot; (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.
3 stage slide switches really hard to get a hold of, I've looked several times. Do you know anywhere good?
<p>https://www.sparkfun.com/products/9609</p>
allelectronics.com 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 :)
Hi <br>can have the circuit you made to have the design<br>thanx
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<br><br>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.<br><br>sorry for bad english, I'm from Serbia :)
<p>I am from the US, and your English is better than most Americans'. Please do not apologize. :-)</p>
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 :)
<p>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: <a href="https://www.instructables.com/id/Rechargeable-Zippo-LED-flashlight/" rel="nofollow">https://www.instructables.com/id/Rechargeable-Zippo...</a><br>Just wanted to say thanks again for the inspiration! :)</p>
Emergency USB back-up lighting :) although always on.
just add a micro switch in between capacitor and led loollolol <br>
hi what if i use 1.0F Capacitor ,,, will i get longer pereiod of discharge and what is the difference?
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.
Absolutely.. that much of capacitance will initially make nearly short circuit current,<br>damaging the USB port... this is a good idea to place a low ohm resistor to charge capacitor...
Why not just throw a diode in to prevent discharge?
Ya, notice about that issue, and I actually update a new circuit at step 7 and step 8 with the charging resistor included.
Very interesting item. Nice <a href="http://www.bestprices.in.ua/ledchasy.html" rel="nofollow">led</a>
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.
2 Farads?!?!?<br><br>Isn't that more than twice than earth's capacitance?!
Why?
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? <br>p.s. Im looking toward ideas for a handy emergency light source
hi, relative newbie here, but how would you suggest wiring 5x capacitors to the circuit. forgive me i am new. thanks
To use 5 capacitors, simply parallel them.
Nice. I want to make one with a pair of <a href="http://www.goldmine-elec-products.com/prodinfo.asp?number=G17960">these</a>.<br>
What voltage does the LED need to be?
A white LED uses 3.0 VDC.
The forward voltage for White LED is around 3V.
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?
awesome! how much was teh capacitor? i want to make this in a little flash drive case.
whats the need of knowing the polatiry
if you dont connect it right the capacitor will short circuit make the capacitor hot and maybe make it explode.
will you get shocked to sh%^ if you touch the capacitor leads or?
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.
you will however start to discharge the capacitor and it may shorten the time from plugged in to no more light.

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