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Discussion Starter · #1 ·
I know there is massive info on the failures of the aftermarket taillights from D2moto here. However, I bought a smoked one (well it may or may not be a D2 moto but it's for sure made in china) off e-bay before I researched them here. So, after reading about the failures I decided to do a little investigation into the taillight that I had bought and see if I could find out why they might be failing before I went to the trouble of installing it.

What I found was a little troubling from an electronic design standpoint and might be the reason for so many failures.

As some of you probably already know, LEDs run on pretty low voltage (2-4 volts or thereabouts) and low current (20-100 milliamps). So, when you have a 12 volt system (actually it can be as high as 15) you need to install a resistor to limit the current through the LED and drop the voltage to something it can handle. The resistor has to dissipate the extra power to prevent the LED from just frying the second you put power to it.

Inside the taillight there is a simple switching circuit that provides for the running light, the stop light and the L and R turn signal functions. Then for each LED (there are 15 LEDs with some being red only down the center and the others being bicolor to perform the turn function) there is a resistor that drops the voltage and current to something the LEDs can handle.

The problem comes in with the wattage rating of those resistors. I connected the taillight to a 15 volt supply and measured the voltage drop across the resistors and then calculated the wattage that each had to dissipate. The result was pretty bad. They are dropping .8 watts through resistors that are only rated to .25 watts (this is all at 15 volts which is a realistic potential supply voltage). 1/4 watt resistors don't last long running at .8 watts. It's a no wonder that guys were losing LEDs because if the resistor burns up the LED no longer lights. After just a few seconds, the resistors were screaming hot.

The other slightly disturbing issue is with the resistor that is used to drop the voltage to the red LEDs when in running light only mode. That resistor has to dissipate 1.4 watts and I don't think it's rated for more than 1 watt. Again, run a resistor that much higher than it's rating and it doesn't last very long. Again, after just a few seconds the resistor was screaming hot.

One way to fix t would be to use higher power resistors for each LED and for the taillight function. The problem is that putting in resistors with a high enough power rating would about $30 just for the resistors (about $1 each). That's about what I paid for the light. And, while it does solve the problem, it's not a very efficient way to do it.

My solution (and I think it will work) is to install a 5 volt regulator (it's just a 3 leg chip) and then I will switch the 5 volts to each LED circuit with a MOSFET. That way the resistors can be 1/4 watt which makes them pennies each (the resistance will have to be diff with the 5 volt supply). The 5 volt regulator is less than $2 and the MOSFETs are about $.75 each (will take 4).

I know I could probably wait for D2moto to come out with the new design but since I didn't buy mine from them I won't be able to trade it in.

Anyway, I'll let you know how it turns out.

Tracy
 

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Great info bro. Hope it works out. And, it might be a clue to them on the new design if they do have failures.

My question is why is the stock light never having one issue vs. all the other problems from aftermarket?
 

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Great info bro. Hope it works out. And, it might be a clue to them on the new design if they do have failures.

My question is why is the stock light never having one issue vs. all the other problems from aftermarket?
Inferior/poor quality parts:dontknow:
 

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I agree, great info. I also agree, why is the stock light not having any problems? Oh, the resisters supplied with the D2moto light are supposed to be used just for the turn signals to get the flash rate down to a normal point. I have one customer where we did not use those resistors and in a small amount of time LED's burnt out on the turn circuits--never having a problem with run/stop circuits. Bought a new light and still did not use the resistors and he is still going strong. So, are there resistors in the circuit behind the outer cover hiden from view? Also, by your calc's, that would mean that using the turn signal alone would be pulling close to 1amp on each flash---correct? Just seems really high for LED's and I wonder what the real rating of the LED is they are using. Why not use a better rated LED?
 

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Discussion Starter · #5 ·
My question is why is the stock light never having one issue vs. all the other problems from aftermarket?
I'm sure that Suzuki did a better job of getting the right components in the OEM light.

Matching the resistors with LEDs is really a simple task. I can't understand why they would have done such a poor job of it on the aftermarket light.
 

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Discussion Starter · #6 ·
I also agree, why is the stock light not having any problems?
I'm sure Suzuki (or the vendor that makes the OEM light for them) did a better job of getting the components right.

Oh, the resisters supplied with the D2moto light are supposed to be used just for the turn signals to get the flash rate down to a normal point. I have one customer where we did not use those resistors and in a small amount of time LED's burnt out on the turn circuits--never having a problem with run/stop circuits. Bought a new light and still did not use the resistors and he is still going strong.
The external resistors are there only to make the flasher circuit on the bike think that it's connected to standard bulbs to keep the flash rate slow. They don't do anything for the internal LEDs of the light itself. They just fool the flasher.

So, are there resistors in the circuit behind the outer cover hiden from view?
Yes. They are on the PC boards that the LEDs are mounted to.

Also, by your calc's, that would mean that using the turn signal alone would be pulling close to 1amp on each flash---correct? Just seems really high for LED's and I wonder what the real rating of the LED is they are using. Why not use a better rated LED?
Each resistor is using .8 watts which is only .07 amps. So the resistors in each turn signal side (6 resistors) is using .42 amps. The LEDs themselves appear to be running at 70 milliamp current so add that (another .42 amps) and you;re pretty close to the 1 amp load. But, they are running these LEDs at 70 milliamps to get the brightness needed and there are 6 on each side (15 total with the center red only ones) so that is still a pretty small load overall.

The LEDs don't seem to be the issue. It appears that the issue is with undersized resistors having to dissipate more energy than they are designed for.

I am also looking at pulsing the power to the LEDs. This might allow them to be quite a bit brighter but still able to work without burning up. If I can pulse them at twice the current but at a duty cycle slightly less than 50%, the LEDs could be close to 15X brighter and you will never know they are being pulsed (just like a lightbulb in your house that runs off 60 cycle AC, it turns on and off so fast that your eyes think it's on all the time).

We'll see.
 

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Discussion Starter · #7 ·
The plot thickens

Was working with the light on the bench and one of the switching transistors crapped out already.

One side of the reds are now no-op.

For sure gotta beef things up.
 
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