LED Lightbulb

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Introduction: LED Lightbulb

About: Working my dream job in the Telecom industry, so chances are, i'll never have time to respond to comments or messages, nothing personal.

This was just a lark that had been itching in the back of my head for a while. It's a mains powered LED lightbulb.



Step 1: Supplies

There's not too many things you need for this project.
An incandescent light bulb.
A .47 microfarad 200V capacitor.
1/4 watt 1kilo ohm resistor
a pair of leds
and miscellaneous things.


Step 2: Assembly

You need to start by cleaning out the lightbulb, there are numerous instructables with this step and I will forgo it here.

The circuit consists of two LED's wired in opposition, I ground down the LED's just short of the die and glued them together to make a single double LED. Twist the legs of the LED's together, on one side solder the capacitor, the other the resistor. Simple.


Step 3: Test

Here I'm holding the circuit with a clothespin and sticking it into an outlet, this is of course, the recommended test procedure. ;-)


Step 4: The Bulb

Stick the circuit into the bulb and use some hot glue to hold it in place, be sure to have some cold water, you will burn you fingers. Try to center the LED in the bulb. Once you have the circuit in place, bend one of the leads over the base and secure it with aluminum tape. The second lead is twisted around a brass screw inserted into the hot glue. Check for shorts and you should be good to go.


Step 5: The How What and Why

First to address an oversight, you need a non polarized capacitor for this project, muy importante.

Now, how does this work? We all know that to run an LED off a higher than rated voltage source we muct limit the current with a resistor. Indeed in this case we could limit the current with a resistor of value approx. 6.8K ohms, however that resistor would need to dissipate several watts!!! Not a good thing.

Since we are using an AC source we can take advantage of a property of a capacitor subjected to AC called Reactance. We can equate reactance to resistance. Calculating the reactance is a simple formula

R=1/(2*Pi*Freq*C) Solving this for C will give us the size capacitor we need to limit the current to the LED.

So why do we have a resistor at all? When the power is switched on there is an in rush of current and the 1K ohm resistor is there to limit that in rush current.

Finally, Why two LED's? Well an LED is a diode and since we are dealing with AC here we need to wire two led's in opposition so that the waveform can complete it's cycle. Essentially each LED is flickering at 60HZ but in opposite phase.

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    123 Discussions

    0
    ajones40
    ajones40

    8 years ago on Introduction

    If I live in the US, should the capacitor be 110v? Standard wall outlets are 110v here.

    0
    andr3w99
    andr3w99

    8 years ago on Introduction

    I have a question... since i am young, i order from a VERY cheap website... they are the same quality items & i would like for you to help me...
    i order from www.TaydaElectronics.com this website is EXTREMELY cheap, but sometimes it is hard to find what you are looking for. Can u help me find the 47 microfarad 200V Capacitor & the 1/4 watt 1kilo ohm Resistor... i dont want to order something, have it turn out its not the right type[s] and have it burn or shock me... thanks

    0
    boyrock375
    boyrock375

    8 years ago on Introduction

    by the way be careful cleaning out the bulb.....when breaking the glass base inside there is an inert gas in there so be sure your carefully and i suggest doing the initial breakage outside

    0
    .Unknown.
    .Unknown.

    9 years ago on Introduction

    How much current do you think this thing draws, roughly?

    0
    qwerty156
    qwerty156

    9 years ago on Introduction

    Hey!

    I pulled out a capcitor from one of those cheap chinese flashlights that charge from ac
    It looks a bit like this
    http://www.surplus-electronics-sales.com/Zencart/images/products/120-1002%20p1%20radial%20mylar%20cap.gif

    Do you think i should give it a try?


    I live ina 230v area

    0
    omnibot
    omnibot

    Reply 9 years ago on Introduction

    Whoa! If you're not sure you shouldn't mess with high voltage! That stuff WILL hurt you. Go through the calculations and read up on the capacitor and safety. Then try it but NEVER mess with mains voltage if you feel uncertain about anything.

    0
    qwerty156
    qwerty156

    Reply 9 years ago on Introduction

    i saw your post just after i tried it lol!

    Anyway, the resistor burn out but the leds are fine.

    Protip - DO NOT TOUCH THE CAP! Nasty suprise!

    0
    Sowee
    Sowee

    Reply 9 years ago on Introduction

    Probably it was damn hot and he burned his fingers.

    0
    qwerty156
    qwerty156

    Reply 9 years ago on Introduction

    nope, it was a shock. scared the crap out of me!

    0
    wd0013
    wd0013

    9 years ago on Step 3

    To:Tool Using Animal

    Awesome post. I especially like the usage of a filter cap in lieu of a (very unnecessary) bridged rectifier. I like bridged rectifiers in larger arrays, but simplicity is always more elegant. Keep 'em coming!

    To: Everyone else

    As an engineer that does waaaaaaay more dangerous experiments than this, let me tell you all that:

    A: There's not enough current draw from that small apparatus to do anything really harmful to the cloths pin. During a malfunction, the cloths pin could get charred, but there would be absolutely NO fire.

    B. At the end that is being held (the side with the LED - this side of the resistor and cap), there is only a miniscule amount of power. It takes high voltage to create any kind of arcing across the cloths pin (much less to the fingers pictured here). I'm talking 500+ volts. Voltage levels of 120 - 240 (depending on which country you're from) simply will not arc in such a fashion. Honestly, though you would feel it, there is (most likely) so little power (on the LED side) that you could comfortably touch the leads for a couple of seconds, as long as it was only one hand touching. Of course body chemistry, grounding, humidity, your own level of intelligence , and many other factors means that mileage will vary here. DON'T BE STUPID - MY RESPONSE IS SHOWING THEORY NOT PRACTICE!

    The reality is that "real world" electronics testing in the A/C world is typically (at least) this dangerous. Common sense, knowledge, and study are your best friends in the lab (at home or work), so read a book folks!


    ONLY THOSE THAT THINK FOR THEMSELVES SHOULD EVEN READ THIS RESPONSE - SHEEPLE GO ELSEWHERE!

    0
    dany_mid
    dany_mid

    11 years ago on Step 5

    hi I live in Europe and here my socket electricity has 220V at 92 mA 50 hz please could you tell me what capacitor should i use?

    0
    Adam Manick
    Adam Manick

    Reply 9 years ago on Step 5

    Your socket does not put exactly 92 mA. You have to measure it with a load. I think you can use 2 of these capacitors.

    0
    Adam Manick
    Adam Manick

    9 years ago on Step 5

    A variable capacitor can give you adjustable voltage

    0
    jules15
    jules15

    10 years ago on Introduction

    How did you come up with the .47uf cap.. i want to know how to make other voltages like 6,9,12.. Is there a formula?

    0
    manuhui
    manuhui

    11 years ago on Step 5

    Hi, if i want to put more than 2 LED, lets say 8 or 10, I put them in pairs, each pair opposite and with their resistor, in parallel or in series ? is that viable ?

    0
    megapix
    megapix

    Reply 10 years ago on Introduction

    You would put the pairs in series, and you would still only need one resistor and capacitor for the string. There are a couple of instructibles which do exactly that.

    0
    noingwhat
    noingwhat

    Reply 10 years ago on Step 5

    I have the same question, I have an idea for a simple 9 LED array that should make it so that it will work almost as well as a traditional bulb. I just don't exactly know the circuitry for it, and this ible was a good place to start. I still need to know if I should put them in series or parallel though.

    0
    noingwhat
    noingwhat

    10 years ago on Step 2

    Is it really necessary to wire two LEDs in opposition? Is the flicker noticable if you didn't?

    0
    megapix
    megapix

    Reply 10 years ago on Introduction

    Yes, its necessary, but not because of flicker. LED's have a "reverse breakdown voltage" of only about 5 volts, so a single LED would break down as soon as the line voltage reversed direction. Although the capacitor and resistor might prevent instantaneous destruction, the LED lifetime would likely be reduced. By putting a second LED across the first LED, with opposite polarity, the two LED's protect each other from high reverse voltage, and double the light output, and reduce flicker. What a deal!