I've taken a basic electronics class and I've been in honors, AP and college level physics so I know a little bit in the area, but there's always more to learn.

I just bought an undertail and I want to make the tail lights my own. They are the two little circles (devil eyes?). I thought it would be cool to make the left light illuminate (in series) counter clockwise while the right light simultaneously illuminates (again, in series) clockwise.

That's probably super confusing.

But what do I need to place between each LED to cause a slight delay? I'm talking a fraction of a second. Is it just a resistor? Something more complex?

 

Simply put, that is a lot more complex than you probably want to deal with. No, it would not be simply a resistor to delay each LED as all that would do is dim each LED. My first thought on this would be extremely complex as you would need an individual LED driver for EACH LED, then you would need a sort of "master timing circuit" that would keep each LED driver off until its time to turn on (giving a delayed effect). After thinking about it a little bit, since everything is DC, you might be able to get away with possibly capacitors in series with your resistors idea. This series RC circuit would have to be in parallel with the LED (to prevent current flow from going to the LED). If you make sure that the capacitors are discharged before you send power to these tail lights (either from brake or blinker), when you DO send power to them, the capacitor has to charge up before current will pass to the LED. The resistor values would regulate how long it takes the capacitor to charge up before it allows current to flow to the LED. Unfortunately, this is not a perfect solution for two reasons:

1) Each individual LED still needs its own series RC filter.

2) When the capacitor is first receiving current from whatever signal it may be, there will be virtually no current going to the LED (as long as you make sure the path of least resistance IS the capacitor UNTIL IT IS CHARGED). However, once the capacitor comes closer and closer to being fully charged, a little bit of current will trickle to the LED. Basically, this is less of an on/off switch and more of a time-proportional switch.

Now, if you wanted to add some transistors and other little goodies in there, you could make a really good circuit, but I'm not sure where your skill level is.

Anyway, I hope this helps give you a better scope of how involved this project would be to make from scratch. You might want to look into something that's already made. There might not be anything specifically for motorcycles, but that's ok, check everything.

 

WOW thanks for the response, I'll be reading that over and over! I'm not the best (or even close to it) with electronics but again, I want to learn.

Now another stupid question, could I use the components of an integrated tail light for my brake light? Because some turn signals light up in series (start in center and light up towards the outside). Could I use this for my brake light while keeping my running lights? And I obviously need my brake lights to not blink....

Damn this is confusing :/

 

You could probably gut an existing product and try to make it work, but no garantees from me on that one. Depends on the number of individual LEDs in the gutted unit and # that you actually need (they really should match), power, signals, size, ratings, timing, etc, etc, etc. The list goes on. To truly answer that question I would need more details of what you're trying to gut and what you're trying to use it for/in.

If I were to try and tackle what you want, I would definitely start with the original LED units that come with the undertail and add "control units" that would control how the LEDs are timed. All custom. There are just too many variables in trying to gut an existing motorcycle product and make it work for something you're trying to do. Plus, doing it from scratch is more fun

One thing I missed from your first post, how are you wanting the LEDs to actually illuminate? During a turn signal only? 100% of the time? During braking only? Do you want it to look like there is only one LED that is lit up and it is rotating around the circle (only one LED on at a time)? Or do you want one LED to light up and stay lit, then the next, then the next, and so on? I have a feeling you are wanting during braking only. So when you first apply the brakes, they light up in order, but stay lit the entire time you are holding the brakes. Then, once you let off the brakes, your running lights are all that are lit?

Edit: Have an idea for a custom one. Use a 555 timer chip in Astable mode to create the frequency you want the LEDs to illuminate in. Feed these pulses into a counter circuit. Counter will output a binary number. Use a multiplexer to decode the binary number into a certain number of outputs (# of LEDs per "devil eye" tail light). Connect each output from the multiplexer into a flip-flop that will "lock" on. Each flip-flop feeds an individual transistor that turns the LEDs on. Haven't figured out how you would reset the flip-flops and counter after you release the brakes yet. Many ways to do it, just gotta find one that's simple...

Edit 2: Ok, I realize the above sounds intimidating, but it's really simple.

 

Yeah you're on track. Its for braking only. For simplicity lets say there are 12 leds in a circle for each devil eye. I want the left eye to light up from 12-11-10-9-8-7-6-5-4-3-2-1 o'clock, while the right eye simultaneously lights up 12-1-2-3-4-5-6-7-8-9-10-11 (so Both 12's light, then 11 and 1, then 10 and 2, etc). Once a light illuminates it stays lit until I let off the brakes. Now what is this 555 timer you're talking about?

 

OK, that's what I thought on the LED lighting order. The 555 timer is an IC (chip) that can handle all sorts of timing depending on how you wire it. It has basically 2 modes, monostable and astable. Monostable handles making a pin (on the chip) high for a certain amount of time (turn something on for a certain duration). Astable mode turns a pin on and off at a certain frequency (square wave, basically a clock signal). You can change the frequency of this square wave depending on what value capacitors and resistors you wire in with the chip. What you would use this for is to feed the clock signal to the counter so that the counter increments at the frequency you want the LEDs to turn on in. Since the counter outputs a binary number, a multiplexer is needed to determine which LED is to be turned on. The flip-flop (latch) is needed to keep that LED on once it is turned on, and the transistor is used simply as an electronic switch to turn the LED on. After you release the brakes, you simple need to reset the flip-flops and counter to turn all the LEDs off at the same time.

Tell me how many LEDs are in each tail light, and how they are arranged, and I can work up a schematic for you to better visualize it. I can also simulate it to show you that it works the way it needs to. I could even make it for you if you really need me to.

 

Okay my undertail comes in soon (I really hope at least) so I will let you know asap. I ordered 36 red superbright leds and I would like to fit as many as I can into each devil eye (in a circle, I'm not going to fill the circle with leds). I'll let you know asap, thanks so much I'm glad theres such a wealth of knowledge here

 

One thing you need to consider with this project (which I didn't even think about till now), is that all the LEDs in your desired system will be wired in parallel. This means that they will draw more current when they are all on. Also, you need to make sure that the LEDs are rated for 12V (unless you want to run a voltage regulator, which gets a little more complicated). Since the LEDs will draw more current, you need to make sure you have wiring in the bike (and a fuse) that can handle the current. What are the specs on the LEDs? (current and voltage ratings)

 

I got them from superbrightleds.com They are the 3mm red ones, here is what they give for specs

3mm LED RL3-R5030 Specifications

 

stupid me, the LEDs I bought weren't for 12v power. I can just put a resistor in and it will be okay though, right? (for series, parallel would need a resistor on every bulb yes?) Should I pick up a handful of 470 ohm resistors?