9v LED Flashlight - Teh Best Evarrr!




Introduction: 9v LED Flashlight - Teh Best Evarrr!

About: I'm entirely self taught in electronics, although I do have a chemistry degree which I currently don't use at all in my day job but that's totally okay! Currently studying robotics, Arduino, microcontroller p…

I know this project's been done a few times here on instructables, but as with many projects there are several ways one can get the same result. I personally think that this setup is the best and easiest for beginnners. Also, it's reusable!

I whipped up this little project from scratch as a means to teach my thirteen-year-old cousin how to solder about a month and a half ago. He did all of the soldering that you see in this instructable (and not bad at all! He's a natural!) He liked the flashlight so much that I think he still carries it around with him!

Step 1: The Parts

Honestly, the design of this is as simple as it gets. It's even easier than another project here that houses the LED inside of the 9v battery clip.

What you will need:

1) Hard plastic 9v battery clip
2) tactile switch (tact switch)
3) Jumbo LED or really bright LED, whichever you prefer
4) proper resistor(s) for your LED
5) 9 volt battery - duh
6) hot glue gun and cheapo soldering iron with solder

The battery clip, LED, and resistor(s) can all be purchased at RadioShack or some other similar electronics store. The tact switch came out of an old broken VCR - check some old junk electronics that have buttons that click, and you'll probably find some tact switches inside. However, you could buy them new from digikey.com or something like that if you wanted to. If you are going to get your tact switch out of something, though, you'll probably need to use a desoldering iron (or something similar) to remove it. A solder sucker works just as well.

Step 2: What LED to Use and What Resistor to Use

My cousin and I used a big red LED on this one because it would be neat to use it on campouts (you know, so it won't supposedly ruin your nightvision). Also, because we had it on hand. If you're making a flashlight that you actually hope to use, then I suggest using an LED that has several thousand millicandella (mcd). I have some around here that I've used before that have 10,000 mcd! Now that's bright!

As many of you know, any time you ever use an LED you should have a resistor in front of it. How do we know which one to use? Well, you could be a nerd and do the calculations yourself or simply go to this website and have it done for you. Word on the street is that's what all the cool kids do.

Step 3: Throwing It All Together

Now that you have the parts that you need, it's time to get to the fun stuff.

The easiest way to go about this would be to hot glue the tact switch, LED, and resistor in place before messing with any solder. If you do this, then you can cut the wires to just the perfect length and your friends will be very impressed with your soldering prowess. Oh, and make sure you do the next steps WITHOUT the clip attached to the battery. Whew, that would have been a bad idea...

Use a wire stripper to strip just a little bit off of the ends of the wires (after you've cut them to the right length), dip them in flux (or lemon juice if you prefer), and tin the wires (put some solder on them so that they'll attach easier when you're making your connections). The flux (or lemon juice) will make the solder spread nice and evenly over the wire. Trust me, even first-timers can figure this out.

In case you're totally new to this, your LED will have two leads coming out of it - one will be longer than the other. That one's positive, the other's negative. Also, sometimes the plastic of the LED will be slightly flat on one side. That side's negative.

The rest follows pretty logically - connect the black wire to the negative lead of the LED. Connect the red wire to one of the four leads coming off of the tact switch. Connect the resistor to the lead that is diagonally across the switch from where you connected the red wire. Then connect the other end of the resistor to your LED. After checking to make sure you connected everything correctly, snip off the extra two leads on the tact switch that you didn't use.

Throw on some more hot glue to make sure everything holds, add some red tape because it just rocks so hard (or leave it naked, that works too), and you have just made yourself one heck-of-a great beginners project / LED flashlight!

Step 4: Closing Comments

I know that there are several cheap LED flashlights out there that you could probably buy for the same price it takes to build this. PLEASE DON'T LEAVE COMMENTS TELLING ME THIS. Thank you.

The point of this lil' project is that if you're trying to teach someone or yourself how to solder, this is a great project that isn't particularly dangerous and there shouldn't be too large a chance for failure (unless you burn out your LED because you wanted to see if it works without the resistor... that's a no no). Also, it's a useful project for a rainy day for you electronics hobbyists who probably have all the necessary parts just laying around already (like I did).

Obviously, there are ways to modify this project such as adding a switch to make it stay on without having to press the button, but I say this setup encourages energy conservation! Yeah, that's it - it's efficient and will make your battery last longer! Plus, since you didn't mangle the battery any and the entire thing is housed on the hard plastic battery clip, you just switch out batteries when you need to.

One definite way to cut the cost of this project is if you're making several of these (say for a Boy Scout troop going on a backpacking trip?). Since many parts come in packages of more than just one item, then you might as well make a few while you're at it!

Thanks for reading and I hope I inspired at least someone to burn their fingers with hot glue in an effort to make something that's fun and kinda useful!

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9 years ago on Introduction

The BLOCKLITE 9V LED flashlight has solved your problem, It is easier to use.


16 years ago

I'm not sure what resistor to use because I got my LED out of a dollarstore LED flashlight. The LED is perfect and works for some reason. It's a bright white light. It came with 2 Lithium Batterys CR2016 3V. So would I have Supply Voltage= 9, Voltage Drop Across LED= 6, Desired LED Current= 20?
It doesn't say what kind of LED or what not that it is. I'll give some pictures.

Lamp - High Powered L.E.D.
Batteries - 2 Lithium Coin Cells
Burn Time 12-14 Hours
Beam Angle - 20 Degrees
Weight - 7 Grams With Batteries

monday, september 11, 2006 001.jpgmonday, september 11, 2006 003.jpgmonday, september 11, 2006 004.jpgmonday, september 11, 2006 005.jpg
Brian Henderson
Brian Henderson

Reply 16 years ago

I'm afraid I don't know the answer to your question. Anyone else know?


Reply 12 years ago on Introduction

 i have super bright  led that takes 3.5 to 4 watts.  how many resistors and what type would I need


Reply 14 years ago on Introduction

(9v-6v)/.020 amps = 150 ohm.

You need a 150 or 160 ohm resistor.


Reply 13 years ago on Introduction

the 3v cells are probably linked in parallel. that means that the voltage is 3 volts. not 6. try that calculation again with that. you will probably get around 330 ohm.


Reply 15 years ago

G'Day Pete,

Firstly, I'm an Aussie, so my spelling will seam odd (Colour Vs Color)

I have various LED keylights like yours. In fact I have the exact one !
I paid AUD $2.99 (+/- US 75c = $1 Aussie)

Anyway, your figures are out, brother. (I M Very H O)

My guess is that these leds look they have a yellow reflector,
when you look into them (when they are not powered).

i.e. they are water clear but the internal reflector dish is pale lemon colour...

My guess is they are about 10,000 mcd and draw 30mA with a max of 100mA.
(Guess plus source: "page 76" of Jaycar catalogue - Part Number: ZD-0194)
They are fine off a pair of 3v lithiums because the disc cells can only output "x" amount
of current and have high internal resistances. (I read that somewhere... I think)

That negates the need for a resistor.

Connect the same LED to a Lead Acid or worse DC power supply and you'll watch
your LED ($$$) extinguish promptly.

B T D T (Been There Done That).

Mind you, you can always reassemble the keylight and then return it to the vendor saying...
"It don' work ! Can ya swap it over for one tha' does please mate?"

They wont have a clue... and will swap it over (...at least once anyway. GRIN)
... Though it is not very honest.
How do I sleep at night??? I dunno....

Meanwhile back at the ranch, tension mounts...
And falls off again !

The calc for the resistor is as follows:

Note: Dots are to space the equasion, as multiple spaces are ignored by the web page

.......... (Vs - Vled)
R = -------------------
.............. I LED

R is the Resistor value
VS is Vsource.
VLED is Volt drop of LED
ILED is the Current draw of the LED

VS minus Vled divided by ILED = required Resistor value.

Resistance required = (Supply Volts minus Volt drop of LED) divided by the
Current draw of the LED.

(9v-3.5v) = 5.5v
divided by 35 mA

157 ohm resistor.

Closest Resistor values are 150R or 160R
(source: "page 58" of Jaycar catalogue)
160R is the safe pick.

Ah, but how do I know all this stuff?
I'm not qualified, nor in the industry...
I'm not tall, not too smart (OK, I lied, I'm reasonably smart - GRIN)

I learned all this 5hit by quizing my buddies and grabing all the electronic's store's catalogues !
Try these...
jaycar.com.au (or jaycar.com, I guess)
soanar.com.au (Wholesale but you can B/S your way into a catalogue as I did !)
You can learn a lot, as I did/have/am/will.
Cats make great ref libraries. Free ones at that too !

Naturally, I won't get away with standing on my soapbox like this...
If you found an error in my post...
Please be nice when posting any corrections/errors/boo-boos.
My ego is not impervious to machine gun derision !

I did my best and am human. Humans do make mistakes.
My intent is honourable.. to help.
I hope this has helped.

- eight from Oz

My huge thanks to "Big Bad Brian" and Anthony... my mates...
(Also any share of any derived kudos, from this post. HaHa !)
Because I drive them both totally insane with my perpetual questions about
basic electronics, formulas, component ID's, "What if's" and "Can I do that's"...

As yet, neither have murdered me (Yet !!) for the ongoing electronic inquisition !!

T-Y-V-M Brian & Anthony.

To be fair, Brian took my old Audi and Anthony took my Ex.

We all seem to be happy with the deal and still get on famously.
Personally, I think I got the best deal, though Brian managed to sell the old car at a small profit, so....
Go figure !

: P


Reply 13 years ago on Introduction

Hi there, I think the 'reflector' you speak of is actually phosphor. I think the way white LEDs work (at least the ones that don’t mix red, green and blue together) is that they're really blue LEDs, but with phosphor on top of the glowing bit. The blue light shines onto the phosphor and then re-emits the light in a wider, whiter-looking spectrum. This is why white LEDs give a slightly cold, blueish light.


Reply 13 years ago on Introduction

Ummm, I had thought that the composition of the junction material was the cause of the colour. GaAs etc. I could well be wrong though. Perhaps there are phosphors, but I have a feeling not. The colour of the white led does change with voltage, though.


Reply 13 years ago on Introduction

Yes, that material does decide the colour of the emitted light, and the most common type of white LEDs are blue LEDs. But (as I said above), the phosphor (the yellow bit that you see when the LED is off) is positioned between the part that gives off the blue light and the outside world, and when the blue light (or sometimes UV LEDs are used, too) falls on the phosphor, it makes the phosphor emit a wider spectrum of light.

There are other methods of making white LED lights, such as tri-colour LEDs that contain red, green and blue LED components in one LED, but the blue/UV LED and phosphor approach is still the most common.

Here's a (US government) site that backs this up (if briefly):


"White light can be achieved with LEDs in two main ways: 1) phosphor conversion, in which a blue or near-ultraviolet (UV) chip is coated with phosphor(s) to emit white light; and 2) RGB systems, in which light from multiple monochromatic LEDs (red, green, and blue) is mixed, resulting in white light."

There's more information on good old Wikpedia:




And on this page, there's a close-up picture of the phosphor in an LED (more of a surface mount-type LED, I think, but the same kind of technology):


You might have a different kind of white LED, but those are the most common. The colour may change when you change the voltage due to a different mix of the blue light from the blue LED components and the other light wavelengths emitted by the phosphor part, but now I'm guessing.


Reply 13 years ago on Introduction

Well, I don't like being wrong, but it costs nothing to say so. On that basis, you win, I was wrong. Ta for updating my education. :) Dave


Reply 15 years ago

So short way to say it is that I should use a 160 resistor?


Reply 15 years ago

You saying I talk too much Peter? HaHaha I think thata 160R resistor is the go, but I'll get a second opinion for you. Famous Anthoy is popping in for a coffee in 6 hours (12.30pm GMT +8 Hours Thursday 5th October) I'll bounce it off him and get back to you. If you are feeling rich, I'd just go with it. I am as stated, guessing on the actual LED and have no way of knowing the spec. I will personally try out what I suggested and post back. I have the bits here. FYI, Resistors are ubber cheap. just cents each at full retail even at the highes tollerances. I suggest spending a $1 and grabbing a few values so you can power off various sources. E.G. Old Cell Phone battery, a few Metal Nikle Hydrides or NiCads. A Cr123 (or similar) larger camera battery. Even hanging a few together, and powering by your old analogue video camera battery. I hope I have helped. P.S. a "Thank You eight" would be a nice touch. Hmmm? To which I would certainly reply... You are most welcome Peter" : P


Reply 15 years ago

o_O big comment.....


Reply 15 years ago

Thanks eight. . . Lol, I keep thinking you look like that icon of yours. AhhHhHhh!!


Reply 14 years ago on Introduction

Your led will probably be an ultra-birght white led. They usually run on around 3v, so you should type in as follows - Supply Voltage= 9, Voltage Drop Across LED= 3, Desired LED Current= 20. The 3v lithium batteries were probably linked in parallel so the voltage would have just been the same as one battery. You would probably need around a 330ohm resistor.


Reply 14 years ago on Introduction

PetervG, you forgot to turn on the lights for those pictures, so they show nothing usable.