LED street lights in N scale

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Marker68

New Member
Okay so I purchased street lights to begin adding to my layout...but they are LED and are way too bright for the look I'm wanting.. how in the world do you dim these things down...any help would be appreciated. I saw a post once about painting them...that didn't work.
 

GeeTee

Well-Known Member
Standard run of the mill LEDs are usually around 2V for Vfwd .Higher voltages will destroy the LED . Without knowing exactly what you have , its difficult to make a recommendation.

The lights you have may or may not have series resistors to reduce the current / voltage on the LED . So we need more information on what you have.
 

Marker68

New Member
Yeah this is all new to me as far as this...but yes 18vac to lights and now that explains why I one I hooked up melted 🤣🤣🤣🤣 no resisters on the lights of any kind..it appears that I need to add a resistor to each light I install...any recommendations
 

GeeTee

Well-Known Member
Ok typical max draw for an led is roughly 20ma . Using ohms law R = V/I , R = Vr / Ir , Vr = 18 - 2 = 16 , the current Ir = I led = 20 ma . 16/.02 = 800 ohms . 1 k is pretty close for max brightness , you could try high as 100 k for a very dim light.

So I would not go below about 1k ohms . Keep in mind if you use DC it will be brighter . Flicker may or may not be noticeable at 50 -60 hz AC with the 50% duty cycle ( the led is diode and will only conduct on one half the AC wave) .

This assumes a standard off the shelf T 1 3/4 Led , most small LEDs will be around the same . Some of the ones that are used in commercial illumination can have a higher voltage (3 or 4).

The best thing to use is a DC walwart with a small ajustable voltage regulator
reg.JPG



You can then vary the voltage output to get the brightness where you want it. This one is good for at least .5 A ( 25 - 50 leds) and cost about $1 in Qtys of 10 .https://www.ebay.com/sch/i.html?_nkw=lm317+voltage+regulator+board&_sop=15
 
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GeeTee

Well-Known Member
If you decide to use the regulator I would use a 5-7V walwart and go with 330 ohm resistors . Going with higher input voltage will cause the regulator to have to dissipate more heat.
 

Iron Horseman

Well-Known Member
Okay so I purchased street lights to begin adding to my layout...but they are LED and are way too bright for the look I'm wanting.. how in the world do you dim these things down...any help would be appreciated. I saw a post once about painting them...that didn't work.
As the others have or and implied, the short simple answer is "add a larger value resistor". All the ohms law stuff is for running a resistance (light bulb) at full brightness without blowing it out. You don't need anything that precise as an LED is not a light bulb. At the power levels we run, for a dim light, try a 5K resistor. If still to bright increase the ohms, if not bright enough decrease.
 

Marker68

New Member
As the others have or and implied, the short simple answer is "add a larger value resistor". All the ohms law stuff is for running a resistance (light bulb) at full brightness without blowing it out. You don't need anything that precise as an LED is not a light bulb. At the power levels we run, for a dim light, try a 5K resistor. If still to bright increase the ohms, if not bright enough decrease.
Thanks for the help... yes the resistors did the trick.
 




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