I recently purchased a set of station platform lamps from China (Wehonest.. seen a few posts about buying from them in the forum) and the LED lamps came with resistors having a grayish-tan body and at least a blue stripe and a red stripe. Less distinct there may also be a dull gold stripe, but it's hard to discern against the tan body of the resistor. The resistor is 5 mm long. Do I need to insert the resistors in series to make the LEDs work? What voltage supply should I use? 1.5? 3? 9? 12?
Thanks in advance for any suggestions
Ed
Getr a multimeter. Even the cheap Harbor Freight ones will work. Use the resistence setting to measure the resistor. Once you know the resistor value you know what voltage you can use.
Or, use your own resistors. ROugh rule of thumb, 470 ohm fo 4-6 volts, 1K for around 12 volts. Those are safe minimum values. The LEDs may be too bright at those values, you can always use a larger resistor. At some point you will have too much resistance for the LED to light, but even 10K at 12 volts will probbaly still light up with a nice dim glow.
If you tilt the resistor in bright light, you may be able to discern the colors. Some of the colrs though, just do not show up against those light blue resistoors - I hate the things. I know the color code by heart, but these days I end up measuring most of them because I can't distinguish some of the colors.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Ed,
Does the package say what the rating is for the LED lamps? If it doesn't, you can hook up both wires of the lamp to the (+) and (-) terminals of a AA or AAA battery to see if it lights up. If not then tape together two batteries and try the same thing.
My guess is that the lamps are 3V and the resistor is for hooking them to a 12V power supply.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Probably they are 3v led's.
I plan or running a DC bus for lighting, but am undecided as to voltage. There are adjustable wall warts from 3-12v. There are also 9-24v which you don't want. There are also inexpensive "Buck step down" regulators on Ebay where you can dial in a voltage.
In any event, you will probably want a resistor unless you are running off battery power. You have two variables, your power supply and the resistors you choose to use. Resistors are also cheap on ebay, so don't feel you have to use the supplied resistors.
I've added 2.2K resistors to my leds for interior lighting and at this point I can say they aren't too bright with 12 v for some things, but for others, like a small miners shack, I will probably add the buck regulator to bring the voltage down.
If you are "picky" on the end result, you are going to have to experiment with voltage or resistance.
Henry
COB Potomac & Northern
Shenandoah Valley
BigDaddyI plan or running a DC bus for lighting, but am undecided as to voltage. There are adjustable wall warts from 3-12v. There are also 9-24v which you don't want. There are also inexpensive "Buck step down" regulators on Ebay where you can dial in a voltage.
A few years ago I bought a wall wart at a discount store. All the different setting gave 12 volts output.
A Walmart one worked fine.
Dave
Randy -
Thanks. I have a multi meter but didn't even think of using it to check the resistance. even though I frequently use it to check battery voltages.
Tom --
They came in a teeny plastic zip lock with no labels or data. I think your idea about them being 3V with the resistor for a 12 V supply might be right. Now to go check.
Thanks,
I have been using the harbor freight meters for some years. 1k allows about 9ma at 12 vdc.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.