I was wondering if you could wire 2 LEDs to the same resistor for headlights? It seems to me the load would not be significantly different than 1 LED. If I wired the positive end of the LED to the same resitor, would that be acceptable for headlight wiring? It seems to me that this would simplify wiring to a decoder.
see 2 SMD LEDs on 1 resistors
wire both LEDs and the resistor in series so that the same current flows thru both LEDs. One LED may be brighter than the other if the LEDs are wired in parallel.
greg - Philadelphia & Reading / Reading
I've wired two LEDs in series on a single resistor AND have wired two LEDs in parallel on a single resistor. Both ways have worked just fine. Never experienced any difference in light output of the parallel version - they are plenty bright anyway.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Having never had to use math, some years ago, I put three LED's in series into a loco using a 330 ohm resistor. I remembered seeing 1k for a single LED which allowed about 9 ma. I just divided 1000 by three and picked a 330 resistor out of the junk box.
I keep a chargeable 12 volt battery, a 1k pot and a 2.5 k pot, and some multimeters for doing LED's plus a well stocked junk box. Need this stuff when working at the component level.
Using a 1k pot, I verified this by lowering the pot so I saw 9 ma current. Pretty simple.
Might be why I have mentioned 1k resistor before for three LED's. Forgot about the 330 ohm resistor. Only did that in one diesel. Two number boards and the headlight.
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.
Hello all,
As long as you don't defy the laws of physics the short answer is yes! (See my signature.)
That's the "theory" what is your application?
In your post you talk about headlights.
Are you talking about dual headlights; one above the other?
Two separate ones? One over the cab and the other on the hood.
Are you considering driving two LEDs from one resistor in parallel?
Basically a "Y" from the resistor to the anodes and then a "Y" to the cathodes.
Or, are you thinking about powering one LED from a single resistor and then powering the second LED from the "output" of the first resistor- -series?
How much room do you have in your application?
Are you trying to save space, wire or resistors?
If you are wiring in parallel or series you probably won't detect the difference of lumens with you eyes.
On my pike I invoke "Rule 17".
For the RS11 loco; with a decoder that doesn't support "Rule 17" functions, I wired the headlight LEDs in "step-down" series.
Each end of the loco has dual headlights; one above the other.
From the decoder I wired one resistor to the cathode. From the anode I wired another resistor, of the same value, to the cathode of the second LED at the opposite end of the loco.
This, in effect, reduced the voltage going to the second resistor and decreased the lumens of the second LED.
To further the effect the second LED is amber- -replicating the dimmed headlight under "Rule 17".
I put the "dimmed" headlight on the top of the headlight stack.
Now, when the direction is changed, the headlights respond accordingly.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"