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Re: [Model_Railroads_Of_Southern_California] Re: White LEDs

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  • Bill Hess
    Bruce : I think that you have a problem with 2 V white LED. LED’s are not like light bulbs . LED’s have a minimum operating voltage. I looked up the
    Message 1 of 9 , Jun 1, 2013
      Bruce :
       
      I think that you have a problem with 2 V white LED.  LED’s are not like light bulbs .  LED’s have a minimum operating
      voltage.  I looked up the specs. for a lot of white LED’s and the starting voltage was around 3 volts.  You may not be able to
      find any LED’s that will run on two volts.  You may need to use a separate circuit with a diode and a 1.2 k / 1/8 or 1/4 watt resistor
      to power the white LED.  For an LED to light, the input voltage must be higher than the forward voltage drop of the LED.  If you use a diode—resistor
      combination, the diode will make the LED turn on in one direction only and the 1.2 K resistor will limit the LED current .  Ohms law /  I = V/ R
                                                                                                                                                  I = current    V = voltage   R = resitance
       
      Bill
       
       
       
       
      Sent: Friday, May 31, 2013 11:02 PM
      Subject: [Model_Railroads_Of_Southern_California] Re: White LEDs
       
       

      You should try digikey.com. They are a huge electronic component warehouse in the Midwest.

      --- In mailto:Model_Railroads_Of_Southern_California%40yahoogroups.com, "brucehendrick@..." <brucehendrick@...> wrote:

      >
      > I am having
      trouble finding a white LED that will work at 2 volts. I want to replace the yellow headlight on an HO Bachmann DCC FT. The LED connection on the circuit board only produces 1.9 volts so LEDs purchased at Radio Shack or Ovac don't work as they need over 3 volts. Walthers lists lots of white LEDs but usually does not list the voltage.
      >
      > Any help is appreciated.
      >
      > Bruce Hendrick
      >

    • texastandp
      You can look at this page and their products. http://ngineering.com/. They have a line of LED products suited for model railroading. Louis Ward
      Message 2 of 9 , Jun 1, 2013
        You can look at this page and their products. http://ngineering.com/. They have a line of LED products suited for model railroading.

        Louis Ward

        --- In Model_Railroads_Of_Southern_California@yahoogroups.com, "brucehendrick@..." <brucehendrick@...> wrote:
        >
        > I am having trouble finding a white LED that will work at 2 volts. I want to replace the yellow headlight on an HO Bachmann DCC FT. The LED connection on the circuit board only produces 1.9 volts so LEDs purchased at Radio Shack or Ovac don't work as they need over 3 volts. Walthers lists lots of white LEDs but usually does not list the voltage.
        >
        > Any help is appreciated.
        >
        > Bruce Hendrick
        >
      • catena888
        have you tried Frys.com? they have a lot of different items and they ship everywhere. How about your local electronic store? I go to mine, tell them what I
        Message 3 of 9 , Jun 1, 2013
          have you tried Frys.com? they have a lot of different items and they ship everywhere. How about your local electronic store? I go to mine, tell them what I want to do, show them what I'm working with and they sell me what I need. I would skip Radio shack since they don't really sell electronic parts like they used to do. it's more cell phones and latest trends that they sell.

          --- In Model_Railroads_Of_Southern_California@yahoogroups.com, "Bill Hess" <rrhess@...> wrote:
          >
          > Bruce :
          >
          > I think that you have a problem with 2 V white LED. LED’s are not like light bulbs . LED’s have a minimum operating
          > voltage. I looked up the specs. for a lot of white LED’s and the starting voltage was around 3 volts. You may not be able to
          > find any LED’s that will run on two volts. You may need to use a separate circuit with a diode and a 1.2 k / 1/8 or 1/4 watt resistor
          > to power the white LED. For an LED to light, the input voltage must be higher than the forward voltage drop of the LED. If you use a diodeâ€"resistor
          > combination, the diode will make the LED turn on in one direction only and the 1.2 K resistor will limit the LED current . Ohms law / I = V/ R
          > I = current V = voltage R = resitance
          >
          > Bill
          >
          >
          >
          >
          > From: Gunnerdaddy
          > Sent: Friday, May 31, 2013 11:02 PM
          > To: Model_Railroads_Of_Southern_California@yahoogroups.com
          > Subject: [Model_Railroads_Of_Southern_California] Re: White LEDs
          >
          >
          > You should try digikey.com. They are a huge electronic component warehouse in the Midwest.
          >
          > --- In mailto:Model_Railroads_Of_Southern_California%40yahoogroups.com, "brucehendrick@" <brucehendrick@> wrote:
          > >
          > > I am having trouble finding a white LED that will work at 2 volts. I want to replace the yellow headlight on an HO Bachmann DCC FT. The LED connection on the circuit board only produces 1.9 volts so LEDs purchased at Radio Shack or Ovac don't work as they need over 3 volts. Walthers lists lots of white LEDs but usually does not list the voltage.
          > >
          > > Any help is appreciated.
          > >
          > > Bruce Hendrick
          > >
          >
        • FADELY GARY
          I agree. LEDs actually work at around 1.2V, because almost any LED you purchase today has an internal current limiting resistor that requires a higher voltage
          Message 4 of 9 , Jun 1, 2013
            I agree. LEDs actually work at around 1.2V, because almost any LED you purchase today has an internal current limiting resistor that requires a higher voltage to fire the PN junction of the LED, but another, typically lesser voltage to continue to light.
            what you are looking for is a component LED, not a packaged LED. Component LEDs will always list three voltages, the turn-on voltage, the operating voltage, and the maximum reverse voltage tolerance (the highest reverse polarity voltage the LED can withstand before the LED is destroyed). You always have to provide the turn-on voltage but the operating voltage is less a concern because LEDs are current driven devices not voltage. As long as you have something close to the operating voltage the internal dropping resistor will limit the current. If the LED output voltage is only 2V, you won't be able to have any current limiter or diode in series. The LED will probably have to be directly connected to the output of your circuit board to turn-on and operate.
            The other two things is to be careful when you are soldering. Always use an alligator clip on the lead near the LED bubble to sink the heat from the soldering iron away from the LED. And make certain you have a good solder joint. A cold joint may have too much resistance and the LED will never fire, especially if you're as close to the turn-on voltage as it seems.
            Otherwise, Bill is correct. You're going to have to pick up 12V from the incoming rail voltage, or at least something closer to the 3V in the rather obtuse spec to operate the LED.
            Gary
             
            Gary Fadely
            5535 Westlawn Ave
            Apt 255
            Los Angeles, CA 90066

            From: Bill Hess <rrhess@...>
            To: Model_Railroads_Of_Southern_California@yahoogroups.com
            Sent: Saturday, June 1, 2013 5:44 AM
            Subject: Re: [Model_Railroads_Of_Southern_California] Re: White LEDs
             
            Bruce :
             
            I think that you have a problem with 2 V white LED.  LED’s are not like light bulbs .  LED’s have a minimum operating
            voltage.  I looked up the specs. for a lot of white LED’s and the starting voltage was around 3 volts.  You may not be able to
            find any LED’s that will run on two volts.  You may need to use a separate circuit with a diode and a 1.2 k / 1/8 or 1/4 watt resistor
            to power the white LED.  For an LED to light, the input voltage must be higher than the forward voltage drop of the LED.  If you use a diode—resistor
            combination, the diode will make the LED turn on in one direction only and the 1.2 K resistor will limit the LED current .  Ohms law /  I = V/ R
                                                                                                                                                        I = current    V = voltage   R = resitance
             
            Bill
             
             
             
             
            Sent: Friday, May 31, 2013 11:02 PM
            Subject: [Model_Railroads_Of_Southern_California] Re: White LEDs
             
             
            You should try digikey.com. They are a huge electronic component warehouse in the Midwest.

            --- In mailto:Model_Railroads_Of_Southern_California%40yahoogroups.com, "brucehendrick@..." <brucehendrick@...> wrote:
            >
            > I am having trouble finding a white LED that will work at 2 volts. I want to replace the yellow headlight on an HO Bachmann DCC FT. The LED connection on the circuit board only produces 1.9 volts so LEDs purchased at Radio Shack or Ovac don't work as they need over 3 volts. Walthers lists lots of white LEDs but usually does not list the voltage.
            >
            > Any help is appreciated.
            >
            > Bruce Hendrick
            >

          • sailboat_sixteen
            Here is an untested idea, since I do not have a DCC circuit board with and LED driver on which to try it, but I will suggest it anyway. It happens that the
            Message 5 of 9 , Jun 2, 2013
              Here is an untested idea, since I do not have a DCC circuit board with and LED driver on which to try it, but I will suggest it anyway. It happens that the cheap garden solar lights currently offered by the 99 cent stores operate a white LED using a 1.5V AAA re-chargeable battery. I took one apart and replaced the battery with a DC power supply and the LED lights from roughly 1.0V up to 3.0V with roughly the same brilliance.

              There is a circuit board in these solar lights that has a 4 lead component on it, and this circuit actively converts the 1.5V up to the needed 3V to run the white LED. The White LED is actually operating pulsed, and if you swing the light around you can see that the LED is being driven with a square wave at probably 100 or 200 Hz, which is associated with the voltage up-conversion process.

              I used a true DC supply, and it is possible that a DCC controller may actually be applying a pulsed signal to the LED. The pulsing may interact with the LED's circuit that is performing the up conversion of the voltage through its own pulsing process, so there may be some issues that I do not know about.

              The semiconductor material used for the LED determines the required forward bias junction voltage. The red LEDs used GaAlAs and could run on 1.5V. The white LEDs are using a semiconductor of a different material that has a higher forward bias junction voltage (I think some may use GaN which delivers invisible UV light and this excites a phosphor that glows white).

              This idea will require one to accommodate the circuit board in the 99 cent solar light that drives the white LED, which looks to me to be about the same size as some of the DCC controller circuit boards I have seen, so there may be some issues with size. However, it stands to reason that there may be a manufacturer that has incorporated the circuit needed for the voltage conversion into the LED package. I would explore some of the small Key Chain white LED lights that typically use a single button battery, for these may be so small that they have to use an LED with this conversion circuitry in the package.

              Don H
              Torrance CA



              --- In Model_Railroads_Of_Southern_California@yahoogroups.com, FADELY GARY <fadely.gary@...> wrote:
              >
              > I agree. LEDs actually work at around 1.2V, because almost any LED you purchase today has an internal current limiting resistor that requires a higher voltage to fire the PN junction of the LED, but another, typically lesser voltage to continue to light.
              > what you are looking for is a component LED, not a packaged LED. Component LEDs will always list three voltages, the turn-on voltage, the operating voltage, and the maximum reverse voltage tolerance (the highest reverse polarity voltage the LED can withstand before the LED is destroyed). You always have to provide the turn-on voltage but the operating voltage is less a concern because LEDs are current driven devices not voltage. As long as you have something close to the operating voltage the internal dropping resistor will limit the current. If the LED output voltage is only 2V, you won't be able to have any current limiter or diode in series. The LED will probably have to be directly connected to the output of your circuit board to turn-on and operate.
              > The other two things is to be careful when you are soldering. Always use an alligator clip on the lead near the LED bubble to sink the heat from the soldering iron away from the LED. And make certain you have a good solder joint. A cold joint may have too much resistance and the LED will never fire, especially if you're as close to the turn-on voltage as it seems.
              > Otherwise, Bill is correct. You're going to have to pick up 12V from the incoming rail voltage, or at least something closer to the 3V in the rather obtuse spec to operate the LED.
              > Gary
              >
              > Gary Fadely
              > 5535 Westlawn Ave
              > Apt 255
              > Los Angeles, CA 90066
              >
              >
              > >________________________________
              > >From: Bill Hess <rrhess@...>
              > >To: Model_Railroads_Of_Southern_California@yahoogroups.com
              > >Sent: Saturday, June 1, 2013 5:44 AM
              > >Subject: Re: [Model_Railroads_Of_Southern_California] Re: White LEDs
              > >
              > > 
              > >Bruce :
              > >
              > >I think that you have a problem with 2 V white LED.  LED’s are not like light bulbs .  LED’s have a minimum operating
              > >voltage.  I looked up the specs. for a lot of white LED’s and the starting voltage was around 3 volts.  You may not be able to
              > >find any LED’s that will run on two volts.  You may need to use a separate circuit with a diode and a 1.2 k / 1/8 or 1/4 watt resistor
              > >to power the white LED.  For an LED to light, the input voltage must be higher than the forward voltage drop of the LED.  If you use a diodeâ€"resistor
              > >combination, the diode will make the LED turn on in one direction only and the 1.2 K resistor will limit the LED current .  Ohms law /  I = V/ R
              > >                                                                                                                                            I = current    V = voltage   R = resitance
              > >
              > >Bill
              > >
              > >
              > >
              > >
              > >
              > >From: Gunnerdaddy
              > >Sent: Friday, May 31, 2013 11:02 PM
              > >To: Model_Railroads_Of_Southern_California@yahoogroups.com
              > >Subject: [Model_Railroads_Of_Southern_California] Re: White LEDs
              > >
              > > 
              > >You should try digikey.com. They are a huge electronic component warehouse in the Midwest.
              > >
              > >--- In mailto:Model_Railroads_Of_Southern_California%40yahoogroups.com, "brucehendrick@" <brucehendrick@> wrote:
              > >>
              > >> I am having trouble finding a white LED that will work at 2 volts. I want to replace the yellow headlight on an HO Bachmann DCC FT. The LED connection on the circuit board only produces 1.9 volts so LEDs purchased at Radio Shack or Ovac don't work as they need over 3 volts. Walthers lists lots of white LEDs but usually does not list the voltage.
              > >>
              > >> Any help is appreciated.
              > >>
              > >> Bruce Hendrick
              > >>
              > >
              > >
              > >
              >
            • Bill Hess
              Don: A voltage multiplier circuit may be a good way to generate enough voltage to operate a white LED. A white LED simply will not operate on 2 volts. There
              Message 6 of 9 , Jun 2, 2013
                Don:
                 
                A voltage multiplier circuit may be a good way to generate enough voltage to operate a white LED.  A white LED simply will not operate on 2 volts. There are several 555 IC
                circuits that can be used for a voltage doubling circuit.  A surface mount 555 IC  is very small and thus the circuit would be small.   Also, regular LED’s do not come with
                an internal resistor.  Some LED’s have a electronic circuit built in so that they will operate over wide voltage range. Say 5 to 12 volts DC.  Other  LED’s have a built in circuit
                that makes them blink.  These are good for installing on the tops of oil or gas tanks etc.
                 
                Bill
                 
                 
                 
                Sent: Sunday, June 02, 2013 1:15 AM
                Subject: [Model_Railroads_Of_Southern_California] Re: White LEDs
                 
                 

                Here is an untested idea, since I do not have a DCC circuit board with and LED driver on which to try it, but I will suggest it anyway. It happens that the cheap garden solar lights currently offered by the 99 cent stores operate a white LED using a 1.5V AAA re-chargeable battery. I took one apart and replaced the battery with a DC power supply and the LED lights from roughly 1.0V up to 3.0V with roughly the same brilliance.

                There is a circuit board in these solar lights that has a 4 lead component on it, and this circuit actively converts the 1.5V up to the needed 3V to run the white LED. The White LED is actually operating pulsed, and if you swing the light around you can see that the LED is being driven with a square wave at probably 100 or 200 Hz, which is associated with the voltage up-conversion process.

                I used a true DC supply, and it is possible that a DCC controller may actually be applying a pulsed signal to the LED. The pulsing may interact with the LED's circuit that is performing the up conversion of the voltage through its own pulsing process, so there may be some issues that I do not know about.

                The semiconductor material used for the LED determines the required forward bias junction voltage. The red LEDs used GaAlAs and could run on 1.5V. The white LEDs are using a semiconductor of a different material that has a higher forward bias junction voltage (I think some may use GaN which delivers invisible UV light and this excites a phosphor that glows white).

                This idea will require one to accommodate the circuit board in the 99 cent solar light that drives the white LED, which looks to me to be about the same size as some of the DCC controller circuit boards I have seen, so there may be some issues with size. However, it stands to reason that there may be a manufacturer that has incorporated the circuit needed for the voltage conversion into the LED package. I would explore some of the small Key Chain white LED lights that typically use a single button battery, for these may be so small that they have to use an LED with this conversion circuitry in the package.

                Don H
                Torrance CA

                --- In mailto:Model_Railroads_Of_Southern_California%40yahoogroups.com, FADELY GARY <fadely.gary@...> wrote:

                >
                > I agree. LEDs
                actually work at around 1.2V, because almost any LED you purchase today has an internal current limiting resistor that requires a higher voltage to fire the PN junction of the LED, but another, typically lesser voltage to continue to light.
                > what you are looking for is a component LED, not a packaged LED.
                Component LEDs will always list three voltages, the turn-on voltage, the operating voltage, and the maximum reverse voltage tolerance (the highest reverse polarity voltage the LED can withstand before the LED is destroyed). You always have to provide the turn-on voltage but the operating voltage is less a concern because LEDs are current driven devices not voltage. As long as you have something close to the operating voltage the internal dropping resistor will limit the current. If the LED output voltage is only 2V, you won't be able to have any current limiter or diode in series. The LED will probably have to be directly connected to the output of your circuit board to turn-on and operate.
                > The other two things is to be careful when you are soldering.
                Always use an alligator clip on the lead near the LED bubble to sink the heat from the soldering iron away from the LED. And make certain you have a good solder joint. A cold joint may have too much resistance and the LED will never fire, especially if you're as close to the turn-on voltage as it seems.
                >
                Otherwise, Bill is correct. You're going to have to pick up 12V from the incoming rail voltage, or at least something closer to the 3V in the rather obtuse spec to operate the LED.
                > Gary
                >
                > Gary
                Fadely
                > 5535 Westlawn Ave
                > Apt 255
                > Los Angeles, CA
                90066
                >
                >
                > >________________________________
                > >From: Bill Hess <rrhess@...>
                > >To:
                href="mailto:Model_Railroads_Of_Southern_California%40yahoogroups.com">mailto:Model_Railroads_Of_Southern_California%40yahoogroups.com
                > >Sent: Saturday, June 1, 2013 5:44 AM
                > >Subject: Re:
                [Model_Railroads_Of_Southern_California] Re: White LEDs
                > >
                > > 
                > >Bruce :
                > >
                > >I think that you have
                a problem with 2 V white LED.  LED’s are not like light bulbs .  LED’s have a minimum operating
                > >voltage.  I looked up the
                specs. for a lot of white LED’s and the starting voltage was around 3 volts.  You may not be able to
                > >find any LED’s that will run
                on two volts.  You may need to use a separate circuit with a diode and a 1.2 k / 1/8 or 1/4 watt resistor
                > >to power the white LED.  For
                an LED to light, the input voltage must be higher than the forward voltage drop of the LED.  If you use a diodeâ€"resistor
                > >combination, the
                diode will make the LED turn on in one direction only and the 1.2 K resistor will limit the LED current .  Ohms law /  I = V/ R
                > >Â Â Â
                                                                                                                                                         I = current    V = voltage   R = resitance
                > >
                > >Bill
                > >
                > >
                > >
                > >
                > >
                > >From: Gunnerdaddy
                > >Sent: Friday, May 31, 2013 11:02 PM
                > >To:
                href="mailto:Model_Railroads_Of_Southern_California%40yahoogroups.com">mailto:Model_Railroads_Of_Southern_California%40yahoogroups.com
                > >Subject: [Model_Railroads_Of_Southern_California] Re: White
                LEDs
                > >
                > > 
                > >You should try digikey.com.
                They are a huge electronic component warehouse in the Midwest.
                > >
                > >--- In
                mailto:Model_Railroads_Of_Southern_California%40yahoogroups.com, "brucehendrick@" <brucehendrick@> wrote:
                > >>
                > >>
                I am having trouble finding a white LED that will work at 2 volts. I want to replace the yellow headlight on an HO Bachmann DCC FT. The LED connection on the circuit board only produces 1.9 volts so LEDs purchased at Radio Shack or Ovac don't work as they need over 3 volts. Walthers lists lots of white LEDs but usually does not list the voltage.
                > >>
                > >> Any help
                is appreciated.
                > >>
                > >> Bruce Hendrick
                > >>
                > >
                > >
                > >
                >

              • gswandpacrr
                Bruce, Try Richmond Controls located in Richmond, Texas (281-342-4895). Check out what they offer on line at www.richmondcontrols.com. They have a large
                Message 7 of 9 , Jun 3, 2013
                  Bruce,

                  Try Richmond Controls located in Richmond, Texas (281-342-4895). Check out what they offer on line at www.richmondcontrols.com. They have a large variety of LED's for model railroaders. I have used them several times for my model train LED's with very good success.

                  John

                  Model_Railroads_Of_Southern_California@yahoogroups.com, "brucehendrick@..." <brucehendrick@...> wrote:
                  >
                  > I am having trouble finding a white LED that will work at 2 volts. I want to replace the yellow headlight on an HO Bachmann DCC FT. The LED connection on the circuit board only produces 1.9 volts so LEDs purchased at Radio Shack or Ovac don't work as they need over 3 volts. Walthers lists lots of white LEDs but usually does not list the voltage.
                  >
                  > Any help is appreciated.
                  >
                  > Bruce Hendrick
                  >
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