213 Waring led post

[jmkk]

Looking for the voltage for the lamp post led's on top of the 213 Lift Bridge . My board that controles the motor and leds went bad. I wired the lift motor at 12 volts threw a double pole double throw momentary switch. That worked great, now I am looking for the voltage for the leds. That way I can wire them up direct also. Maybe some body has a 213 lift bridge they can pull a warning led lamp post out of and check the voltage with a meter and let me know. I did contact Lionel Tech support they said thay dont know and have no way to find out.              

 

Thank you. Jason

[lionelsoni]

The open-circuit voltage is not going to be very informative.  You need to design a circuit for the supply voltage you have.  How many LEDs do you have, and what colors?

[jmkk]

 2 Red LED's on top of the bridge. I can pick from 12 or 24 volt's AC on the bus wires running around the layout. The bridge motor pulls 12 volts threw a Bridge Rectifer from the 12 volt buss line. Could I use a 5 volt voltage regulator ?  Would 5 volts be two much? I could splice in the voltage regulator after the Bridge Rectifer and run it to the two LED's.

 Hope that helps. Jason

[lionelsoni]

A regulator wouldn't accomplish anything.  Use the full-wave rectified voltage that you have.  (I assume that you haven't filtered it.)  Wire the two LEDs and a 330-ohm 1/2-watt resistor in series.  Make sure that the cathodes of the LEDs are toward the negative side of your 12 volts:

minus---|<-----|<-----/\/\/-----plus
       LED    LED    330 ohms

The cathode is marked with a shorter lead or a flat on the base of the LED next to the cathode lead.  This site has a diagram that may help you to identify the cathode lead:

http://www.merg.org.uk/led/index.htm

 

[jmkk]

  Just for future knowledge why would a voltage regulator not work?  Just because of the LEDs in series? As an example would it work for a 5 volt lightbulb? No the 12 volt is not filtered. As it stands now the LEDs are not wired in series but that is the way the bridge came from lionel. I can rewire it that way, but I would prefer not to tear it appart again. If there is a way to do it the way Lionel has that end of if wired that would be great.

 

              ------------------         ---------------plus

         LED                           LED

              ------------------        ----------------minus

 

 Thanks again. Jason

[lionelsoni]

The current that an LED draws is very sensitive to the voltage across it.  A little less than it needs and it doesn't light at all.  A little more and it burns out.  The best way to avoid this problem is to put them in series with a "ballast" resistor and run them from a higher voltage.  That is what the 330 ohms is.  It will make the average LED current about 20 milliamperes and keep it close to that value even though the 12-volt supply varies.

You could use an individual ballast resistor for each LED.  In that case I would use 390 or 470 ohms instead of 330.  Wiring the two LEDs directly in parallel, which is what I think you want to do, might work if you are lucky, that is, if the two LEDs operate at almost exactly the same voltage (which is about 1.5 volts for a red LED).  You could try it.  The worst that can happen is that one will be much brighter than the other.  The resistor value for that connection should be about 220 ohms.

Also consider the possibility that Lionel used LEDs with integral resistors.  These do exist.  Unfortunately it would be hard for you to be sure that that's what you've got; and you don't want to risk burning them out by slapping 12 volts on them if they are simple LEDs.

[rlplionel]

Just wondering, Jason, did you ask Lionel if they have a replacement board for your lift bridge? I think installing a replacement board would have been the easiest soluton to your LED problem.

[jmkk]

 Yes they do have a replacement. But for me (personal preferance) I did not like the way they had it wired. Board was a pain to get to were it was at, wire gauge was too light.  All this stems from one derailment on the bridge. the wire that completes the circut for a train too pass threw when the bridge is down melted(22 or 24 gauge) and the board went bad. Replaced that one piece of wire with 14 gauge. Rewired bridge moter with 16 gauge. And now LEDs with 16 gauge wire. I placed the 330 ohm 1/2 watt rersistor under the bridge where I can get to it . Just for info I was using a new cw-80 transformer when this happened. Also everything is isolated from the bridge now.

[lionelsoni]

Do the LEDs light up after all your work?

[jmkk]

Yes. Thank you for all your help Bob.

Thanks again.  Jason