How much Current and Voltage a LED requires?

Discussion in 'Electronic Basics' started by Ibrahim Mohammad, Sep 22, 2003.

  1. Hi,
    If I want to make a normal LED glow how much power shall I supply to it?
     
    Ibrahim Mohammad, Sep 22, 2003
    #1
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  2. Ibrahim Mohammad wrote:
    >
    > Hi,
    > If I want to make a normal LED glow how much power shall I supply to it?


    The voltage required varies mostly with color. Infrared devices take
    about 1.5 volts, red about 2 , green 2 to 3 volts, and blue 3 to 4
    volts. However the LEDs do not pass a very well defined current if
    you supply them with a fixed voltage, and current is what is just
    about proportional to emitted power. Normally, you connect them to a
    voltage that is a bit higher than what they will drop, and include a
    series resistor that will stabilize the current by wasting the extra
    voltage. For instance if you wanted to light a single red LED from a
    5 volt source with a 10 milliamp current (probably about half of
    maximum rated current), you would assume about 2 volts drop across the
    LED, and choose a 300 ohm series resistor because that value would
    waste the extra 3 volts when 10 milliamps passes through it.
    (volts = amps times ohms. so 3 = .01 times 300)

    If you wanted to light a lot of LEDs, you might use the current more
    than once by connecting several in series and using a higher supply
    voltage, allowing 20 to 30 percent of the total voltage to be wasted
    across the resistor, to allow for slight LED voltage drop variations,
    and supply voltage changes. Not designing for the absolute maximum
    rated current allows for less of the total voltage to be wasted by the
    resistor, since a slight error will not destroy the LEDs.

    --
    John Popelish
     
    John Popelish, Sep 23, 2003
    #2
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  3. Ibrahim Mohammad

    JeffM Guest

    120Vac will make it glow--but only till the embers cool.

    Seriously, what John said is right.
    Little digital multimeters can be had for ~$5 USD.
    If you are _ever_ going to touch something electrical again,
    go ahead and buy one now.

    Use it to monitor the current through the LED vs the brightness
    (some are super-bright at low current).
    If you get to 10mA and it's not really bright,
    decide if you are willing to go farther and chance damaging the LED.
    It may handle as much as 25mA continuously--it may not.
     
    JeffM, Sep 24, 2003
    #3
  4. "Ibrahim Mohammad" <> wrote in message news:<3f6ecf9e@shknews01>...
    > Hi,
    > If I want to make a normal LED glow how much power shall I supply to it?


    There are many web pages on the net that will supply you with the
    information you need......there is formula and it isnt a complicated
    one.

    Use www.google.com which is a search engine and look up terms like
    "led", "leds", "powering an led"..... "led projects"......there are
    many decent sites dedicated to the led.......

    I would pot a few links but being as these pages are archived and
    being that any link I post may one day lead to a dead page or broken
    link I will save our children from the annoyance of clicking on a link
    and going nowhere.
     
    cornytheclown, Sep 25, 2003
    #4
  5. Ibrahim Mohammad

    John Fields Guest

    On 25 Sep 2003 09:47:28 -0700, (cornytheclown)
    wrote:

    >"Ibrahim Mohammad" <> wrote in message news:<3f6ecf9e@shknews01>...
    >> Hi,
    >> If I want to make a normal LED glow how much power shall I supply to it?

    >
    >There are many web pages on the net that will supply you with the
    >information you need......there is formula and it isnt a complicated
    >one.
    >
    >Use www.google.com which is a search engine and look up terms like
    >"led", "leds", "powering an led"..... "led projects"......there are
    >many decent sites dedicated to the led.......
    >
    >I would pot a few links but being as these pages are archived and
    >being that any link I post may one day lead to a dead page or broken
    >link I will save our children from the annoyance of clicking on a link
    >and going nowhere.


    ---
    I have a better idea.

    Since you apparently have nothing of value to say, why not stop posting
    altogether?

    --
    John Fields
     
    John Fields, Sep 25, 2003
    #5
  6. John Fields <> wrote in message news:<>...
    > On 25 Sep 2003 09:47:28 -0700, (cornytheclown)
    > wrote:
    >
    > >"Ibrahim Mohammad" <> wrote in message news:<3f6ecf9e@shknews01>...
    > >> Hi,
    > >> If I want to make a normal LED glow how much power shall I supply to it?

    > >
    > >There are many web pages on the net that will supply you with the
    > >information you need......there is formula and it isnt a complicated
    > >one.
    > >
    > >Use www.google.com which is a search engine and look up terms like
    > >"led", "leds", "powering an led"..... "led projects"......there are
    > >many decent sites dedicated to the led.......
    > >
    > >I would pot a few links but being as these pages are archived and
    > >being that any link I post may one day lead to a dead page or broken
    > >link I will save our children from the annoyance of clicking on a link
    > >and going nowhere.

    >
    > ---
    > I have a better idea.
    >
    > Since you apparently have nothing of value to say, why not stop posting
    > altogether?


    I told him to do a google search.....that is the most logical thing
    for someone to do as there are many many sites that will in detail
    guide him thru the info he needs....

    Your post truly added nothing of context to the thread...other than
    showing that the frigid bitch you call your wife once again turned
    your sorry ass down driving you to the internet in a fit of
    rage.........

    I hope coming onto the thread and attempting to "spank" me make you
    feel better..........

    asshole......
     
    cornytheclown, Sep 27, 2003
    #6
  7. Ibrahim Mohammad

    John Fields Guest

    On 27 Sep 2003 09:37:30 -0700, (cornytheclown)
    wrote:

    >John Fields <> wrote in message news:<>...
    >> On 25 Sep 2003 09:47:28 -0700, (cornytheclown)
    >> wrote:
    >>
    >> >"Ibrahim Mohammad" <> wrote in message news:<3f6ecf9e@shknews01>...
    >> >> Hi,
    >> >> If I want to make a normal LED glow how much power shall I supply to it?
    >> >
    >> >There are many web pages on the net that will supply you with the
    >> >information you need......there is formula and it isnt a complicated
    >> >one.
    >> >
    >> >Use www.google.com which is a search engine and look up terms like
    >> >"led", "leds", "powering an led"..... "led projects"......there are
    >> >many decent sites dedicated to the led.......
    >> >
    >> >I would pot a few links but being as these pages are archived and
    >> >being that any link I post may one day lead to a dead page or broken
    >> >link I will save our children from the annoyance of clicking on a link
    >> >and going nowhere.

    >>
    >> ---
    >> I have a better idea.
    >>
    >> Since you apparently have nothing of value to say, why not stop posting
    >> altogether?

    >
    >I told him to do a google search.....that is the most logical thing
    >for someone to do as there are many many sites that will in detail
    >guide him thru the info he needs....


    ---
    You're full of shit. The most logical thing to do, if you respond to
    the post and you know the answer is to post it. It's not like the
    answer is so involved that several pages on the web are required to
    explain how to do it. Here it is:

    P = IE

    Where P = the power dissipated by the LED in watts,
    I = the current through the LED in amperes, and
    E = the voltage across the LED in volts.

    Assuming voltage drop of 2V across the LED ans 20mA of current through
    it, P = IE = 0.02A * 2V = 0.04W = 40 milliwatts. This answers his
    basic question and will allow him to calculate the series resistor
    required for any given supply voltage or, conversely, to calculate the
    supply voltage required for any given value of current-limiting
    resistance.

    What you did was imply that you had the information on how to do what he
    wanted but that you were sending him elsewhere to search for it.

    Then there was that little, "I will save our children..." shit, which
    means you're either too goddam lazy to go looking for a link to help him
    out or you couldn't find one if you tried. I vote for the latter.
    ---

    >Your post truly added nothing of context to the thread...other than
    >showing that the frigid bitch you call your wife once again turned
    >your sorry ass down driving you to the internet in a fit of
    >rage.........


    ---
    Grasping at straws, ****?

    _Anything_ posted to this threads adds to its context. Perhaps you
    meant "substance"?

    As for frigid bitches, if I needed to **** one for any reason I think
    I'd call your dad for leads...
    ---

    >I hope coming onto the thread and attempting to "spank" me make you
    >feel better..........


    ---
    Well, if you consider constructive criticism a spanking, then consider
    yourself spanked and yes, if the critcism has helped you to realize what
    a shithead you are I _do_ feel better for having helped you get a
    glimpse of the real world.

    BTW, Cheeta, it's 'made', not 'make'.
    ---

    >asshole......


    ---
    Is that the best you can do for a parting shot? You need to go back to
    some of your fifth grade chums and see if they can't help you out with
    something a little more worthy of the illustrious minds populating this
    NG.

    --
    John Fields
     
    John Fields, Sep 27, 2003
    #7
  8. I just felt it would be best to send the poster to a few sites where
    he could learn a little more about leds and limiting the current to
    them.....just tossing a formula out here is helpfull but there is so
    much more he can learn from the various websites out there..........


    The original posters question had been answered by a poster previous
    to me..... and the formula and an explanation had been given...I was
    merely pointing out that he could also find websites out there with a
    wealth of information to him... a few very very detailed websites
    devoted solely to leds.... I guess I should have posted a few sites
    but I hate posting something that will be gone tomorrow or next week
    as this happens to so many sites....
    Hopefully his electronics experience is not going to involve hooking
    an led up to a resistor and a battery and ending there......

    anyhow....................


    John Fields <> wrote in message news:<>...
    > On 27 Sep 2003 09:37:30 -0700, (cornytheclown)
    > wrote:
    >
    > >John Fields <> wrote in message news:<>...
    > >> On 25 Sep 2003 09:47:28 -0700, (cornytheclown)
    > >> wrote:
    > >>
    > >> >"Ibrahim Mohammad" <> wrote in message news:<3f6ecf9e@shknews01>...
    > >> >> Hi,
    > >> >> If I want to make a normal LED glow how much power shall I supply to it?
    > >> >
    > >> >There are many web pages on the net that will supply you with the
    > >> >information you need......there is formula and it isnt a complicated
    > >> >one.
    > >> >
    > >> >Use www.google.com which is a search engine and look up terms like
    > >> >"led", "leds", "powering an led"..... "led projects"......there are
    > >> >many decent sites dedicated to the led.......
    > >> >
    > >> >I would pot a few links but being as these pages are archived and
    > >> >being that any link I post may one day lead to a dead page or broken
    > >> >link I will save our children from the annoyance of clicking on a link
    > >> >and going nowhere.
    > >>
    > >> ---
    > >> I have a better idea.
    > >>
    > >> Since you apparently have nothing of value to say, why not stop posting
    > >> altogether?

    > >
    > >I told him to do a google search.....that is the most logical thing
    > >for someone to do as there are many many sites that will in detail
    > >guide him thru the info he needs....

    >
    > ---
    > You're full of shit. The most logical thing to do, if you respond to
    > the post and you know the answer is to post it. It's not like the
    > answer is so involved that several pages on the web are required to
    > explain how to do it. Here it is:
    >
    > P = IE
    >
    > Where P = the power dissipated by the LED in watts,
    > I = the current through the LED in amperes, and
    > E = the voltage across the LED in volts.
    >
    > Assuming voltage drop of 2V across the LED ans 20mA of current through
    > it, P = IE = 0.02A * 2V = 0.04W = 40 milliwatts. This answers his
    > basic question and will allow him to calculate the series resistor
    > required for any given supply voltage or, conversely, to calculate the
    > supply voltage required for any given value of current-limiting
    > resistance.
    >
    > What you did was imply that you had the information on how to do what he
    > wanted but that you were sending him elsewhere to search for it.
    >
    > Then there was that little, "I will save our children..." shit, which
    > means you're either too goddam lazy to go looking for a link to help him
    > out or you couldn't find one if you tried. I vote for the latter.
    > ---
    >
    > >Your post truly added nothing of context to the thread...other than
    > >showing that the frigid bitch you call your wife once again turned
    > >your sorry ass down driving you to the internet in a fit of
    > >rage.........

    >
    > ---
    > Grasping at straws, ****?
    >
    > _Anything_ posted to this threads adds to its context. Perhaps you
    > meant "substance"?
    >
    > As for frigid bitches, if I needed to **** one for any reason I think
    > I'd call your dad for leads...
    > ---
    >
    > >I hope coming onto the thread and attempting to "spank" me make you
    > >feel better..........

    >
    > ---
    > Well, if you consider constructive criticism a spanking, then consider
    > yourself spanked and yes, if the critcism has helped you to realize what
    > a shithead you are I _do_ feel better for having helped you get a
    > glimpse of the real world.
    >
    > BTW, Cheeta, it's 'made', not 'make'.
    > ---
    >
    > >asshole......

    >
    > ---
    > Is that the best you can do for a parting shot? You need to go back to
    > some of your fifth grade chums and see if they can't help you out with
    > something a little more worthy of the illustrious minds populating this
    > NG.
     
    cornytheclown, Sep 27, 2003
    #8
  9. In article <>,
    mentioned...
    > On 25 Sep 2003 09:47:28 -0700, (cornytheclown)
    > wrote:
    >
    > >"Ibrahim Mohammad" <> wrote in message news:<3f6ecf9e@shknews01>...
    > >> Hi,
    > >> If I want to make a normal LED glow how much power shall I supply to it?

    > >
    > >There are many web pages on the net that will supply you with the
    > >information you need......there is formula and it isnt a complicated
    > >one.
    > >
    > >Use www.google.com which is a search engine and look up terms like
    > >"led", "leds", "powering an led"..... "led projects"......there are
    > >many decent sites dedicated to the led.......
    > >
    > >I would pot a few links but being as these pages are archived and
    > >being that any link I post may one day lead to a dead page or broken
    > >link I will save our children from the annoyance of clicking on a link
    > >and going nowhere.

    >
    > ---
    > I have a better idea.
    >
    > Since you apparently have nothing of value to say, why not stop posting
    > altogether?


    John, I agree with you, to a point. He's got as much of a right to
    express his opinion and be an a$$hole as you do. We have a lot
    worse. Which, by the way, I've conveniently taken care of with my
    kill file filters. You might consider doing that also.

    --
    @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
    ###Got a Question about ELECTRONICS? Check HERE First:###
    http://users.pandora.be/educypedia/electronics/databank.htm
    My email address is whitelisted. *All* email sent to it
    goes directly to the trash unless you add NOSPAM in the
    Subject: line with other stuff. alondra101 <at> hotmail.com
    Don't be ripped off by the big book dealers. Go to the URL
    that will give you a choice and save you money(up to half).
    http://www.everybookstore.com You'll be glad you did!
    Just when you thought you had all this figured out, the gov't
    changed it: http://physics.nist.gov/cuu/Units/binary.html
    @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
     
    Watson A.Name - Watt Sun, Sep 30, 2003
    #9
  10. Ibrahim Mohammad

    John Fields Guest

    On Mon, 29 Sep 2003 23:42:46 -0700, Watson A.Name - "Watt Sun"
    <> wrote:


    >John, I agree with you, to a point. He's got as much of a right to
    >express his opinion and be an a$$hole as you do. We have a lot
    >worse. Which, by the way, I've conveniently taken care of with my
    >kill file filters. You might consider doing that also.


    ---
    OK, PLONK!

    Just kidding... :)


    --
    John Fields
     
    John Fields, Sep 30, 2003
    #10
  11. In article <>,
    mentioned...
    > John Fields <> wrote in message news:<>...
    > > On 25 Sep 2003 09:47:28 -0700, (cornytheclown)
    > > wrote:

    [snip]

    > Your post truly added nothing of context to the thread...other than
    > showing that the frigid bitch you call your wife once again turned
    > your sorry ass down driving you to the internet in a fit of
    > rage.........
    >
    > I hope coming onto the thread and attempting to "spank" me make you
    > feel better..........
    >
    > asshole......


    POT --> KETTLE --> BLACK

    Furrfu.

    --
    @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
    ###Got a Question about ELECTRONICS? Check HERE First:###
    http://users.pandora.be/educypedia/electronics/databank.htm
    My email address is whitelisted. *All* email sent to it
    goes directly to the trash unless you add NOSPAM in the
    Subject: line with other stuff. alondra101 <at> hotmail.com
    Don't be ripped off by the big book dealers. Go to the URL
    that will give you a choice and save you money(up to half).
    http://www.everybookstore.com You'll be glad you did!
    Just when you thought you had all this figured out, the gov't
    changed it: http://physics.nist.gov/cuu/Units/binary.html
    @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
     
    Watson A.Name - Watt Sun, Oct 3, 2003
    #11
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