Those specs say they are approximately 2V (that's what I would run them at... LEDs are very picky when it comes to voltage) and 20mA LEDs.

Yes, each LED would need a resistor is series with it. 470 ohms won't work. Since the LEDs need to run at 20mA, if you were to put in 470 ohm resistors, it would put the voltage drop on the LED at 2.6V, which would burn it up considering the max forward voltage on the LED is 2.5V. What you want to do (since you want these to last a long time) is run them at about 2-2.1V. A 500 ohm, 5% tolerance resistor would do this just fine. They also need to be at least 1/4 watt rated (P=I*V=20mA*10V=0.2 Watts; 10V is the drop that needs to be on the resistor in order to keep the LED voltage drop at 2V)

Alright I'll get some resistors...I have an update for now

The undertail came in. One issue though, the devil eyes they gave me are projector looking things(like headlight projectors). Looks way beyond ugly so I'm gonna go find something different to use

Sooo I got my superbright leds today. I mistook 3mm leds for 5mm, so now I have a bunch of tiny ass leds. That's okay though, each ring will look "high def". I can fit 21-22 leds in a ring (I'm calling each devil eye a ring). My only concern is brightness. I took 2 AA batteries out of my camera to see how bright they are. When I use one battery its SUPER dim (1.5v). But when I use two batteries in series (I know, that's past the 2.6v rating) its SUPER bright (this was in my room, so my definition of SUPER bright probably translates to reasonably acceptable for road use). Should I see how they look at 2.1 ish volts? Just ghetto rig some batteries and resistors and get my voltage and current right to see how bright they are before we continue?

I'm sorry, in your last response you say (they) need to be at least 1/4 Watt rated. Did you mean the resistor or led?

I apologize, I meant the resistors need to be at least 1/4 Watt rated. Pics of the tail lights would help me visualize everything a lot. Try and post some if you can.

Yes, running the LEDs at the right voltage and current will give you a much better feel for how bright they will be. Run them at 2.4V, 20mA (2.5v is the max voltage and the max operating current is 20mA). That will give them a good lifetime and still be very close to as bright as they will go.

Snap some pics of the undertail and taillights and post em up so I have an idea of what you're working with and how you plan on mounting the LEDs. Speaking of that, how do you plan to mount the LEDs?

Edit: you say you can fit 21-22 LEDs in each ring. With 21 Leds in each ring, the current draw when they are all on would be 21*0.02=0.42 Amps. That means two things. 1) You MAY NOT need to upgrade your wiring. As long as the wiring is AWG 30 or larger, it will work just fine. 2) You should check what kind of heat those LEDs produce. Too much heat in a small taillight assembly can cause some problems; in particular, reducing the brightness of the LEDs (as LEDs get hotter, they become less bright).

Edit: I was just going to start up a schematic for you, and thought of a couple things. One, since you want the taillights to be symmetric, and "come on" symmetrically, we can simplify the circuitry and have each transistor (used as a switch in this case) turn on one LED from each taillight (total of 2 LEDs wired in series with each transistor). For example, when both the 12:00 LEDs (take a ring of 12 for simplicity in this example, each hour on a clock represents an individual LED) are to be turned on, a single transistor can be used to switch them on. We would have the corresponding LEDs from each taillight wired in series (12:00 LEDs are wired in series to a single transistor, as are the 11:00 LEDs, and so on and so forth).

Second, the more LEDs you want in each taillight, the more complicated the counter circuit and multiplexer must be, as well as the more flip-flops you need. For 21 LEDs in each taillight, you would need a 6 bit counter to have enough combinations to activate all of the transistors. For 12 LEDs per taillight, you would need a 5 bit counter. Not sure on a price difference between these, I just wanted you to know that the circuitry will be more complicated the more LEDs you want.

I'm making my own tail light housing. Again, the ones provided with the undertail looked like projectors and that's SUPER ugly. So I'm cutting Plexiglas and drilling 21-22 holes for lights. I can get some pics tomorrow

Oh OK. What's the brand/model of the undertail so I can try to look it up?

Ah I don't know, I got it off eBay. It was the best looking one I could find without dropping $300 on a mototeck unit.

If you look for it on eBay, its the double signal (two signals on each side) one. They make a single signal version as well. Again, pics in the am

Oh I gotcha. I found it. That is actually very similar to what I was looking at (I have an '04) when I was shopping for an undertail on mine. I heard to many bad things about the brake light/blinker brightness on aftermarket undertails, so I decided to get a hotbodies undertail to allow me to keep my stock brake light.

I was going to start up a schematic for you yesterday, but had a few issues with my computer, so I'll have to do some work on it this weekend. :icon_doh: PICS! PICS! PICS! :icon_teeth:

NOW NOW NOW!!!

several failed drawings of circles and junk
Attachment 46211

the undertail (minus ugly ass tail lights)

Attachment 46212

The disgusting projectors they tried to pass off as tail lights
Attachment 46213

The actual light part (yes, the grey stuff is pvc drain pipe...like the stuff in your house)
Attachment 46214

To give you an idea of how these will look...(I'm drilling holes tomorrow based on this spacing)

Attachment 46215