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LED Electronic Resistors

LED Electronic Resistors

Andy G asks this:

“I have a few 3 volt street lights (LED) that came with separate resistors. Does anyone know how to wire resistors to lights? Thanks in advance.”

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10 Responses to LED Electronic Resistors

  • phil johnsonsays:

    I don’t think it makes any difference. I normally attach mine to the negative wire on my signals and + on street lights

  • Kevin Chingsays:

    Resistors should always be wired to the + side of the LED this will make them last longer they do not like the full voltage on the cathode the resistor is there to limit the current flow.

    • Francis Caves Ceng MIEEsays:

      Wrong. It makes no difference. the same current flows through both.
      The resistor has to be the right value to limit the current through the LED.
      Connect in series (+—-LED—–RES—- -) The LED has to have the Anode connected to the +ve supply.

  • Peter Pococksays:

    Also, adding to a previous comment, if the LED does not light up then swap the Leeds! If you’re using a 12 volt supply I find a 1K (1000 ohms) resistor is good place to start. If you want less brightness, then try anything up to 5K. Quarter Watt resistors will be fine. Bigger, or higher wattages only take up space!
    A small, cheap set of clip on Leeds is a quick way of connecting things up until you have things working, then solder up the various wires etc.

    • Francis Cavessays:

      Leads not leeds.!

  • Sundaramsays:

    Please go to the internet and Type “LED current limiting resistor”. This site gives you various sub contents where one can get the resistor with value that needs to be connected for a Parallel or series LED circuit. One particular site allows to enter the values of current consmed by the LED, the input voltage and the no. of LEDs and it calculates the ressitor value to be used and also the schematic diagram of the circuit if required. Hope this helps.

  • Anselmosays:

    actually you can solder the resistor (1K ohm is the most common used in the hobby) to any of the phase of the led.
    Just make sure the power wire positive phase is conected to the longest leg of the led. The longest leg is always the positive. Of course you will cut these legs to fit your job, so I always keep the positive (anode) a little bit longer than the negative (cathode)

    • Sheldon Clarksays:

      Good idea.

  • Jay Rosssays:

    In my experience with LED’s, I find that some will require more power than others, depending upon the colors. Typically though, they run great on 15ma (.015amp). The formula for selecting the resistors is: R=E/I. Example: If using a 5v supply, 5v/.015=333 ohms. However, with all of that said, I have found a tiny microchip, that when installed in line with an LED, it will regulate the current to 10ma, with a supply voltage input from 3v up to 50v. It can be ordered from Newark Electronics, here is the info:
    60R6439 NSI50010YT1G Tape and Reel Cut 1 120
    $0.186 $22.32
    You install this device in series with the LED. The device has a marker line like a diode, that shows you the negative side. Align both the LED’s negative and device’s negative so that they both are at the correct polarity to the negative of the supply voltage.

  • Roy Carslakesays:

    The formula for finding the correct resistor for any voltage is as follows
    R= (V – 1.7) x 1000 */.I(current)..So a resistor for 12 volts is 12 v – 1.7= 10.3v x 1000=10300 (divided by Current of the LED usually 20mA) ( (0.02A) wich comes out at 515 ohms nearest resistor is 560 ohms

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