I have a led taillight with resistors and am not sure how the resistors get wired in. Thanks for any help.
Sorry, I do not have an LED tail light.. I'm surprised you need a resistor though.. I would contact the company that made the unit..
Can you fill in your profile a little?? What kind of bike do you have and where are you located??
I have used two different LED taillights on my Magna and neither used a resistor. I think resistors are only needed for LED turn signals, so I am 99 percent certain you can install the taillight without using the resistor.
LED stands for Light Emitting Diode -- well, duh, we knew that, right?
The voltage drop across one of these diodes is typically 1.7 to 1.9 volts, depending on the crystal they are made from, which is another way of saying depending on the color of light they emit.
The voltage/current curve is very steep -- the current can increase by a factor of 10 with only 0.2 volts additional drive across the diode.
So, you string a bunch of them together to add up to the voltage you apply, right? So how many are you going to use to get between 12.6 and 15 volts? If you get it wrong, you get either:
a) light not very bright (maybe you see no light at all!) or,
b) burn one (or more) of them up.
So if the diodes say they need a resistor, by all means put in the requisite resistor!
The efficient way to do this is with a switching power supply that regulates the current to the diodes -- a "constant current source" if you will. Given the steep current/voltage curve, this is the only drive that can possibly be efficient.
One can approximate a constant current source with a big resistor that drops most of the voltage, but then the efficiency of the whole system goes in the toilet -- most of the power is burned up as heat in the resistor, and very little becomes light.
See
http://www.theledlight.com/LED101.html
for more details.
Lawrence:
I'm not disagreeing with you, but if what you say is true, then why do so many of the LED taillights out there for sale not come with resistors? I've had two and I have several friends who have used several each, and none, and I really mean none, have come with resistors and none have ever had a problem (lights are bright and none have burned out). What's the deal? Are the resistors just built onto the circuit board on most of the units commercially available? I'm actually very curious about this. I always get resistors included in the package when I get LED turn signals, but never with the taillights. The taillights always seem to be plug and play.
To continue on what Chokse said.. I bought LED Marker lights (6 LEDS per light) to use as blinkers and instead of adding a resistor so the Blinkers would blink correctly, I purchased a flasher unit that doesn't care about load and put out pulses of voltage regardless of load.. I did not put any resistors in front of the LED's... They seem to be working fine..
From my research into making my own Lawrence is dead on. The off the shelf tailights I looked at had resistors built into them. If you look at them really close you can see them down in there. The are small little tubes, usually tan, but color changes with amount of resistance IIRC.
Also, in the blinkers I have looked at, which also recommended I get a relay of sorts to use, you can still see they used a resistor in the light itself.
My .02 cents and certainly not nearly as qualified as Lawrences.
There are resistors on the marker lights as well.. But I changed the Flasher unit to one that didn't care about output current to determine flash rate, otherwise I would have had to add more resistors, which is just a waste of energy to heat..
The taillight does have turn signals, but not being an electrical genius, the diagram that came with the light is a bit confusing to me. I need to know where the resistors get connected and where they go to. Thanks. Doug
Doug, the resistors must connect in series with the LEDs. The LEDs will only work with the correct end toward the battery. It makes no difference whether the resistor is between the battery and the LED string, or between the LED string and ground. Either way will drop the voltage and control the current to within the designed limits.
I believe the resistors are so your Blinkers will blink at the same rate, and not too fast..
So as it was said, it doesn't matter if it's on the Positive side or the negative side, so long as it is in series.. (or you can replace your flasher unit like I did where it doesn't care about load.)
A series resistor will help limit the current through the diode string. This is what I was talking about above. If your blinkers won't work because they are not drawing enough current, that would require a resistor in parallel, across the light string with whatever current limiting series resistors it has in it. This resistor will draw enough current to make your mechanical blinkers work.
Hoot clearly has the better solution -- put in a blinker whose timing is independent of the current that the lights draw, and toss the parallel resistors.
A resistor meant to operate your mechanical blinkers, and wired in parallel will be large -- maybe 3/4 to 1 inch long, 3/8 inch across, with solder posts sticking out both ends, and possible two mounting ears to tie it down to the frame -- which you will need to do to help dissipate the heat. Series resistors to limit the current through the diode string will be smaller, probably about the diameter of the diodes or even smaller, and maybe 1/2 inch long.
Which do you have??
The resistor I have sounds like the first. It's ceramic and about 2" long. Is this flasher you guys speak of "Universal" or made to fit all models, and is it wired in or does it replace the flasher in the fuse box? Thanks. Doug.
Doug, the flasher is universal but is a Plug N Play for the 3rd gen Magnas. This would be for blinkers and not the taillight.
This is the one that Terry Recommended and I now recommend as well.. It's $20 and as Terry stated it's plug and play.. The only strange thing to get used to is it doesn't click... You know Click.. Click.. Click.. Click.. when the blinker is on.. It makes no noise (which it shouldn't) I wonder if I could pay them to make one that clicks!!! (Old School you know!!)
The nice thing for me about this is later if I decide to put LED blinkers in the front, there is nothing else for me to do.. This flasher unit does not care about output..
Model ELFR-1
http://www.customled.com/products/flasher_relay/flasher_relay.htm (http://www.customled.com/products/flasher_relay/flasher_relay.htm)