LED Driver... Noob here and a little lost.

Hi, So I have a motorcycle (2007 Suzuki SV650 for anyone who cares 8)), and the previous owner put aftermarket turn signals it. I like the design, but the LED's arent bright enough. I would like to replace them with higher power LED's (specifically 'Superflux LED's from Oznium.com), and also make the turn signals sequential, aka, when a blinker is on, it has a scroll pattern that runs from the center to the outside.

I have an Arduino Mega, and have messed with it a bit. Enough to know that the LED's I want to install exceed safe current draw from the Mega itself, plus with having the scroll pattern, it would eat up a lot of pins.

Here's what I need help with: Each of the LEDs draw about 80 ma at 2 volts. I need individual control of 6 pairs of LEDs for each side, to be able to animate each blinker. What do I need to do/buy to get the LED's powered and controlled by the Arduino, as well as use as few pins as possible? Having the ability to 'fade' LEDs is important to make the animation smooth and professional looking.

I really appreciate the help, and any explanations would be awesome! I'm just starting, and finally have a project to work on that will drive me, along with many other project ideas. Thanks! XD

http://www.ti.com/product/tlc5940

And a power supply for the LEDs.

Work through the power equation (it's in the datasheet) before committing to the TLC5940.

So, if I understand this correctly, for each output I could connect 2 of my LED's (2v, 80 ma each) in series, making each channel 4 V, 80 ma, and this driver would handle it. Now I'm assuming I would then need to drop my supply voltage into the TLC5940 for the outputs down from 12v (bike battery) to 4V. Would this be acceptable? http://www.amazon.com/DROK-Adjustable-Regulator-Experimental-Converter/dp/B00BYTEHQO/ref=pd_sim_sbs_e_3

Forget the Mega2560 - go get a Pro Mini for the actual implementation. You need a USB to TTL module for programming, which is no longer needed when the system is installed.

Techman_360: So, if I understand this correctly, for each output I could connect 2 of my LED's (2v, 80 ma each) in series, making each channel 4 V, 80 ma, and this driver would handle it.

That would appear to be the case.

Techman_360: Now I'm assuming I would then need to drop my supply voltage into the TLC5940 for the outputs down from 12v (bike battery) to 4V.

Have you measured the LED voltage? I suspect it is somewhat more than 2V for yellow high-brightness LEDs. Probably more like 5V (which is the operating voltage for the TLC5940) or even 6 or 7 volts.

Techman_360: Would this be acceptable?

Looks OK, but will tend to draw current even when not required, if only due to the 7 segment display.

Actually, it appears that the TLC5940 is designed to regulate the LEDs up to 17 volts (must be made for this job), which means if you heatsink it, you can feed the LEDs directly from your battery, given that you fit a 15 volt Zener as a "crowbar" and a 1A fuse.

Ahh, ok. Thanks for the Pro Mini Suggestion

Paul__B: Actually, it appears that the TLC5940 is designed to regulate the LEDs up to 17 volts (must be made for this job), which means if you heatsink it, you can feed the LEDs directly from your battery, given that you fit a 15 volt Zener as a "crowbar" and a 1A fuse.

I think I have a general idea, but why would I need to have a Zener diode, and what is the term crowbar, lol? And I'm assuming this is taking place after the fuse, where my 12v hits the TLC5940 to power the outputs? Noobin it up!

Techman_360:
So, if I understand this correctly, for each output I could connect 2 of my LED’s (2v, 80 ma each) in series

Correct. You can connect any number of LEDs in series up to a 17 V drop (minus the minimum drop through the TLC5940).

making each channel 4 V, 80 ma, and this driver would handle it.

Almost correct. There has to be a voltage drop through the TLC5940. I believe the minimum is 1 volt (check the datasheet). So, each channel is at least 5 V, 80 mA.

There is also a maximum voltage drop through the TCL5940 based on the expected power dissipation.

Now I’m assuming I would then need to drop my supply voltage into the TLC5940 for the outputs down from 12v (bike battery) to 4V.

5 V (or more).

Would this be acceptable? http://www.amazon.com/DROK-Adjustable-Regulator-Experimental-Converter/dp/B00BYTEHQO/ref=pd_sim_sbs_e_3

Maybe…

Ripple Peak: About 100mV

1/10 th of a volt. Seems kind of crappy. I suggest you find a vehicle capable power supply with a lower ripple, no built-in readout, and a fixed output.

Techman_360: I think I have a general idea, but why would I need to have a Zener diode, and what is the term crowbar, lol? And I'm assuming this is taking place after the fuse, where my 12v hits the TLC5940 to power the outputs?

Indeed. Thought you might ask. In automotive applications, you have to allow that you may get voltage surges or "spikes" much higher than the nominal 14V of the charging circuit. The TLC5940 is rated to 17V only, so you need to protect it. A straightforward way to do this is to use a Zener diode which will limit the voltage to 15V, but of course, surges could exceed the capacity of this diode (preferably, one rated at least 5 watts) to handle them, so a fuse is needed to protect it (and indirectly, the rest of your circuit). Supply goes through fuse to Zener and the rest of the circuit.

This is the "crowbar" - something that is strong enough to short circuit such surges, like dropping (or throwing) a crowbar across a mains supply - a somewhat unwise experiment should anyone consider it.

Have you considered the Philips Superflux LED's? They're better quality and much cheaper than the unbranded ones sold by Oznium.

TLC5940 is overkill for this, there is no need for PWM brightness/fading. I would use a 50V capable/150mA per channel shift register, TPIC6B595. http://www.ti.com/lit/ds/symlink/tpic6b595.pdf Simpler to code for as well.

80ma LEDs will be invisible in sunlight, it would be like not having them at all. I've tried many signal LEDs on my motorcycle and finally went back to incandescent because the LEDs all wash out when the sun is shining (oh sure, they look bright when you're standing right next to the bike, but other drivers are hundreds of feet away and are too busy blabbing away into their cell phone to look for dim lights).

Also, LEDs tend to be directional. They're usually only bright straight on -- move off to the side 45° and the brightness drops off dramatically.

Motorcycles are abso-freakin-lutely invisible to most car drivers. You really need to burn their retinas if you don't want them to drive right through you.

I would consider six 350mA emitters to be the absolute bare minimum for each motorcycle turn signal. I've tried commercial amber 3x350mA LED turn signal "bulbs", but they are considerably dimmer than incandescent. If I were building my own, I'd use as many 500mA (Cree XP-E) emitters as I could cram in to the turn signal housing. At these levels, you're looking at dedicated high-power LED drivers such as BuckPucks.

I do have two 1,000mA red LED "bulbs" for my brake lights, though. They are approximately the same brightness as incandescent. For some reason the reds are visually "brighter" than amber for the same drive current. I mention this because if you're Arduino-ing your bike anyway, you could add a brake light "modulator" feature (flash for the first 1-2 seconds or so of brake application).

Thanks all for the responces!

Mike_S: Have you considered the Philips Superflux LED's? They're better quality and much cheaper than the unbranded ones sold by Oznium.

I will look at those! Thanks!

CrossRoads: I would use a 50V capable/150mA per channel shift register, TPIC6B595. Simpler to code for as well.

No kidding, lol, the Tlc5940 library out there isnt a cake walk.. figuring it out, but maybe I'll get a couple of these to play around with.

tylernt: 80ma LEDs will be invisible in sunlight, it would be like not having them at all. I've tried many signal LEDs on my motorcycle and finally went back to incandescent because the LEDs all wash out when the sun is shining (oh sure, they look bright when you're standing right next to the bike, but other drivers are hundreds of feet away and are too busy blabbing away into their cell phone to look for dim lights).

I would consider six 350mA emitters to be the absolute bare minimum for each motorcycle turn signal. I've tried commercial amber 3x350mA LED turn signal "bulbs", but they are considerably dimmer than incandescent. If I were building my own, I'd use as many 500mA (Cree XP-E) emitters as I could cram in to the turn signal housing. At these levels, you're looking at dedicated high-power LED drivers such as BuckPucks.

Thanks for the advice tylernt! I was hoping if I rough up the interior of the lens, it would diffuse the light more, but I know where youre coming from... I'm gonna try these bulbs first, if nothing else for my own curiosity and experimenting, but I have a feeling I will be looking for some of the higher powered bulbs as you mentioned.

If anyones interested, heres a video of what I've gotten so far, not much, but progress in my eyes! http://www.youtube.com/watch?v=ZitM7aatEFg

Thanks all!