I want to replace some incandescent bulbs with LEDs in a couple of diesel locomotives. I have some Miniatronics 5mm YeloGlo White LEDs, and the instructions call for 470 ohm resistors. But, that resistor value leaves the LED way too bright.
So, I tried a 1K ohm resistor, but the result was a still way too bright LED. Then, I tried a 5K ohm resistor. That reduced the brightness somewhat but still too bright.
I wound up with three 5K ohm resistors in series. I finally got a satisfactory brightness level, but that seems ridiculous - - a total of 15K ohms.
Besides, is there any risk of damage with that high a value?
I bought a 0-2 amp meter off eBay that has 5 digits for checking my LED lighting. Silly thing works so good I ordered a second. As I remember they were about $4.
The meter is a panel mount and didn’t come mounted, I bought a box also off eBay to hold the meters. A real handy goodie is a small DC to DC converter for working with LEDs, variable regulated 0-12 volts at 2 amps. I mounted it in a like box, super handy for setting up LEDs.
I use 4 volts for my passenger lighting and I set the converter to 4 volts so I don’t have to screw around setting the voltage on my bench power supply, any power from 5 volts up gives me the 4 volts out.
They (they newer SMD LEDs) are way more efficient than older LEDs - that translate into more light for less current. So having to use much more than the ‘typical’ 1K (which runs a typical white LED at or below half the maximum rating - which is a really good safety margin, at least to keep the LED from frying) is not too surprising. Having to go up to 15K on a more traditional leaded LED - I wonder if they are the same as the YeloGlo LEDs I bought years ago. Could be they are using a new supplier and they are deliverying high efficiency LEDs, which are available in leaded versions - typical red LEDs on 5 volts with a 470 ohm resistor were about right, but the high efficieny ones are absolutely blindlign and light up plenty bright on 5 volts with 1K or more.
There is something to say about the size, since if the light output is equal but one source is a 5mm globe and the other is maybe 1mm in the center of the SMD version, it will appear much brighter to the eye. Much of that though could jsut be losses in the material the LED is made out of - even clear, not diffused, 5mm and 3mm LEDs have a good deal of clear epoxy between the actual emitting point and where you view it. Crank down the current enough and you might be able to hold the 5mm LED up and see the tiny point where the light comes from with it powered.
EEVBlog on YouTube once got hold of a hight sensitive photodetector (like single digit numbers of photos would trigger it) and did a test with some LEDs. Even regulr ones, with insanely low currents - even in the dark your eye, and even better his camera, couldn’t detect a glow - but this sensor did.
The headlight LED was burnt out in a recent purchase of an Atlas Silver series Dash 8-40CW.
I had some smd LEDs and so put one in. Way too bright compared to the backup light. In Lokprogrammer, I tried reducing the brightness but even at the lowest level it was barely acceptable, and the dimmer wouldn’t work any more (not surprising). Atlas have 1K resistors in their LED +ve leads so I tried upping it to 2.2K which is the LokSound default. A lot better.
The thing about LEDs is that they maintain an even brightness way down until they start to turn off. It’s a matter of limiting the current until you find that sweet spot where it’s dimmer but still controllable.
Most of my experience with LEDs has been with bi-polar red-green LEDs. With those LEDs, 1K resistors or less have been fine. And those bi-polar LEDs have primarily been from Miniatronics. But those YeloGlo White LEDs from Miniatronics are just way too bright for locomotive headlights and Mars lights. I have the same problem with SMD LEDs.
In this most recent instance, I tried a 1K resistor - - - way too bright. So, then I switched to a 5K resistor which didn’t seem to reduce the brightness one bit. I added a second 5K resistor in series - - - still seemed to be the same level of brightness. Once I added the third 5K resistor, the brightness dimmed to a satisfactory level.
I use 3mm wide angle Super Bright LEDs for the lighting in my passenger cars and prefer realistic looking low level lighting. I went with 9.1KΩ resistors at 4 volts for the lighting on my current Athearn Mel kitbash lounge car. I used 9 of the 3mm wide angle Super Bright LEDs with 9.1KΩ resistors spaced at ⅞” in the ceiling to illuminate the lounge area and one with a 4.7KΩ resistor over the bar for a total of 4.8ma at 4 volts.
The Super Bright LEDs are very efficient compared to the older LEDs.
Yep, I agree. This isn’t the first time that I have installed the Miniatronics YelGlo White LEDs in a locomotive for the headight or Mars light. I have installed that LED in a few others and the bright light is blinding.
I found some Golden White LEDs this morning from another manufacturer that I had stored in a box. With a 1K resistor on the Golden White LED, the brightness level is much more subdued.
I have a bunch of loco that the headlights are the Miniatronics YeloGlow, with a 1K resistor, and they aren’t excessively bright. Some are 5mm, some are 3mm. My P2K Geeps, my Trainline FA, a couple of my Stewart switchers - they came with an LED that was redily visible throught he headlight lens that was orange when off, so they got swapped. I did change the resistor on that - but they came with 470 ohm and I desoldered those and put in 1K.
FWIW, when I did the interior lighting for my McKeen Motor Car I used 30K resistors, one for each of the 16 or so interior lamps. The LEDs glowed just like a very early incandescent bulb, which was the effect I wanted. In fact, I could have gone with a higher value resitor because when all the lights in the room are out, the interior lamps are still a bit too bright.
As others have said, you can’t hurt the LEDs by trying higher value resistors.
I am not very good with a camera. In fact, I am awful. But, I will try to photgraph one of my Minatronics YeloGlo LEDs with a 1K resistor. Other forum members are reporting the same brightness problem on both this thread and elsewhere on the forum. I cannot understand how your Minatronics YeloGlo LEDs with a 1K resistor installed are not too bright. Why would your LEDs be different than others?
I see that tiny orange spec on my Miniatronics YeloGlo White LED when off. On my Golden White LEDs, the entire “shell” that covers the LED is orange or, maybe better stated, an orangey-amber color.
Sounds liek they are still made the same then. That’s part of why I went with them in the Stewart switchers, since the LED is very visible through the lens they use for the headlight. With a Yelo-Gloe LED in there, it looks like a shint reflector with a small yellow light bulb in the middle when off - if you look close enough the ‘light bulb’ is square but it sure beats seeing orange.
They could be different because the newest ones I bought are all at least 9 years old, most of the installed ones are even older - at least one of the Stewart switchers (those are 3mm ones, not 5mm) based on when and where I took the pictures showing how I bent the leads to match the stock LED was taken 13 years ago. Miniatronics just repackages stuff, they don;t make LEDs, switches, or much else of what they sell. So over the years, their LED supplier could easily have changed.
Mine were purchased more recently than 9 years ago, but I am not sure when exactly.
I did not realize that Miniatronics does not manufacture its own LEDs or incandescent bulbs or toggle switches. They do seem to be better quality parts than what I have purchased elsewhere.
