Station lighting

[adamski]

Evening all

I have a station with 10 of these lanterns from ebay (see copied link.) My main lighting in the buildings is 12v dc led tape, so I have installed a buck converter to drop the voltage down to 3 volts , which is the voltage required to drive the lamp posts. My question is, do I need a resistor? Normally the answer would be yes, but I'm unsure this time, I understand the resistor is there to stop the led from drawing too much. If I do require a resistor what would be the value? I have a second station which only has 3 of these posts, again, voltage dropped down via a buck converter - would it require a resistor and if so, what value ?

https://www.ebay.co.uk/itm/YMY1-17-G-1-22-4pcs-Scale-Train-Railway-Lampposts-Model-Street-Lights-LEDs/123180769567?hash=item1cae25611f:g:s1oAAOSwubRXDd3p

Many thanks in advance

 

[Greg Elmassian]

LEDs operate on fixed current, not voltage. Trying to set them right with a fixed voltage is really a fools errand. Yes, yes I'm sure a ton of people will come out and tell you it works for them.

Newer LEDs are more tolerant of excessive current and light up well significantly below their rated current. Why not put all 4 in series and see if they light well enough from 12 volts?

Forget the converter....

Greg

 

[Gizzy]

You don't need the convertor.

As your LED lamps are 150 mA and you are using 12 V then I would normally use a resistor of 100 ohms for each lamp. Calculated using the formula R=V/I or R=12/0.15

However, depending on how you connect them, if in series, then a 20 ohm or near about resistor would suffice. R=12/(0.15 x 4)....