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Thread: Basic electronics question...

  1. #11
    Maximum Bitrate SjLucky's Avatar
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    yea it can
    it could be done for you...
    Quote Originally Posted by menudude View Post
    thank you all for your help minus the useless post by sjlucky...

  2. #12
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    http://superbrightleds.com/

    As the name implies, they have very bright LEDs

    --Dima

  3. #13
    Variable Bitrate Sh0cker's Avatar
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    since we are talking about LEDs here, i need some help locating online store that carries 3mm Red(high bright) 12V LEDs.
    thx
    Danny.

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  4. #14
    cvi
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    Sorry, i wont speak up again. BUT...
    * He needs more leds connected. (read post)
    * He asked for a 3 Volt resistor.
    Since there are no such thing, the easiest to do are leds in serial. Power coming from the computer psu would give 5V, that makes 2,5 V for each led.
    * He dont have to mess with calculators or make a fool of himself asking for a 3 Volt resistor.
    * It will work.

  5. #15
    Variable Bitrate
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    Quote Originally Posted by cvi
    Sorry, i wont speak up again. BUT...
    * He needs more leds connected. (read post)
    * He asked for a 3 Volt resistor.
    Since there are no such thing, the easiest to do are leds in serial. Power coming from the computer psu would give 5V, that makes 2,5 V for each led.
    * He dont have to mess with calculators or make a fool of himself asking for a 3 Volt resistor.
    * It will work.
    I'm sorry to say, it won't work. An LED when conducting does not drop 2.5 volts. LEDs are misleading. They are CURRENT SPECIFIC not Voltage specific. The resistors aren't really used to reduce the voltage, they are used to limit the current. An LED will operate just fine with only 0.7 volts applied. The Spec on the LED of 3V is a MAX operating voltage, not a voltage requirement. Use the reistors. Or, if you wish, some LEDs are "pre-resistorized" to run TTL (5V) levels without an external resistor.
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  6. #16
    Low Bitrate crosseye's Avatar
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    CVI, just for your future reference, I tried hooking two LEDs in series up to a 5V DC power supply. Both LEDs were lit but got REALLY hot REALLY fast. I took them off before they blew. With a single 22ohm resistor in series with 1 LED, no heat could be noticed by touching the LED.

    Speaking of the "pre-resistorized" LEDs, I have like 6 of them here that i do not need. They are red and supposed to work with 5V. I don't have the packaging anymore so I don't know the exact brightness, etc. They look pretty bright with 5V applied to the terminals.

    If you were looking for an easy way to impliment LEDs with 5V, I can sell these to you for like $0.50 a piece plus another $0.50 for packaging and shipping. You don't need to worry about a resistor with these puppies, just apply a 5V difference to the terminals and you're good to go.

    Email me at [email protected] if interested.

  7. #17
    Raw Wave
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    An LED will operate just fine with only 0.7 volts applied. The Spec on the LED of 3V is a MAX operating voltage, not a voltage requirement.

    Thats not true.

    You need 2V to operate an LED, depending on colour...you need to let it conduct first before it can even light up. The 2-3V is the forward voltage and not maximum operating voltage...thats the voltage it need before it operates.

    Just for the record I just stick a 1.5V on a green LED and nothing.

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