The 12 volt LED is only wired with a resistor to work at 12 volts. It is after all a 3 volt LEd so it does consume less.A 3V LED only needs milliamps to work, that's why you have to have a resistor, and precisely why you use one on a locomotive, I'm not sure how a 12V LED would work, but I would assume exactly like an incandescent bulb which, if correct, defeats the point of switching from incandescent to LED, a 3V LED will give full brightness as long as it has power, even at low speeds.
You can get LEDs that work at 12v without resistors, but in this instance won't do the job required.The 12 volt LED is only wired with a resistor to work at 12 volts. It is after all a 3 volt LEd so it does consume less
I along with a lot of others, I can't get my head around this law, (it just gives me a headache). I have 6 different resistors and I know which resistor will give me the effect I want, ie, a 1/2W 1.5K resistor on a LED will give me maximum brightness using a power supply regardless of whether I'm using 12v or a lightboard on a loco.Use Ohms law to determine the resistance need with a specific voltage.
Thanks Mike, great info as always.some of these answers give me pause led's will light using AC or DC however they should be on DC AC they are pulsing very fast and seem to be lit harder to control
12 volt leds yes but expensive for true ones not for model rr
and yes just a resister with the led will give you directional lighting
resisters control voltage and current yes
what I used is a CL2N3-G led driver can use any dc voltage and only lets 20 ma to the led so constant brightness
if used with a common diode you can get directional lighting
These CL2N3-G are about 49 cents a piece available from numerous places just do a search for CL2N-G led driver
for those in England https://uk.farnell.com/microchip/cl2n3-g/led-driver-temperature-compensated/dp/2448491
if anyone wants further info I can give a link to a site that explains it
Chris here's the site I mentioned and I did work with this kind of stuff for 30 some yearsThanks Mike, great info as always.
You gotta find the fine print...You can get LEDs that work at 12v without resistors, but in this instance won't do the job required.
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I along with a lot of others, I can't get my head around this law, (it just gives me a headache). I have 6 different resistors and I know which resistor will give me the effect I want, ie, a 1/2W 1.5K resistor on a LED will give me maximum brightness using a power supply regardless of whether I'm using 12v or a lightboard on a loco.
If you hadn't said what it was for I would've had a clue.Chris here's the site I mentioned and I did work with this kind of stuff for 30 some years
http://www.trainelectronics.com/LED_Articles_2007/LED_104/index.htm
I forgot here's a resister unit we used at the RR on some battery setups
HA! Variable resister for what, 100 amps?I forgot here's a resister unit we used at the RR on some battery setups
Exactly, no such thing as a "12 Volt LED". When the vendors say that they are using common terms to help folks understand the application.You gotta find the fine print...
"Internal Resistor inside the LED "
Think we're going a little off topic nowExactly, no such thing as a "12 Volt LED". When the vendors say that they are using common terms to help folks understand the application.
I have never more misunderstanding about anything but LEDs. It is a little more complicated and technical, but the rules of thumb I use are:
1. An LED is not a light bulb do not think about it like it is and everything will be easier.
2. An LED IS a diode. Treat it like a diode when planning circuits and things will work.
3. An diode is a creature of current not voltage. That is a diode does not work not on an operating voltage but rather it has a threshold voltage. Once the threshold voltage is reached (usually between 1.4 and 2.2 volts) it then acts like a short circuit. It will try to pass all available current from the supply. With uncontrolled current it will instantly overheat and burn out. It is never voltage that burns out a diode it is the over abundance of current. This is why a resistor has to be in series with the diode, to limit the current.
4. This is also why ohms law doesn't apply to a diode. Ohms law applies to the resistor in series with the diode. There is a small voltage drop through the diode, but practically it is just along for the ride.
(If anyone cares, the diode formula is exponential and given by I=IS(exp(eVηkBT)−1), for which all the variables can be looked up on the web).
5. Diodes are designed to pass current in only one direction, so if it is put in backwards there will be no current flow.
6. Diodes put into an AC current will pass the current for one polarity and block it for the next. In effect a single diode will convert AC to half wave DC.
Then for LEDs specifically:
1. In an AC circuit the LED will turn on and off (60 times per second in the USA), but your eyes generally will not see this.
2. The more current that passes through the junction the brighter it will be. Playing with the resistor value will vary that current amount and allow one to set the brightness and hence the "mood" so to speak.
No, it's a good post if someone wants to delve deeper into the mystery of LEDs they can, but it's their choice to do so.So my earlier post about the exact same thing you must have missed plus the link on how they work and how to use them
So maybe I should just delete my post