Hey all,
Hello!
I’m a motorcyclist and I’m attempting to postpone my early demise.
I’d like to add a couple of very visible LED’s to the mirrors of my bike. I think I have just about enough knowledge of LEDs and electronics to be a danger to myself and others! I’m looking to build something to aid my visibility.
I’d like to make something physically small and unobtrusive but still very visible. I was looking at using a couple of CREE XHP50 J4 Copper PCB emitters since they appear to be relatively small, bright and efficient (pretty much the opposite of myself :laughing: and can be run in 6v or 12v modes giving a little flexibility. Initially I was planning to run them at 100% duty cycle, 50-75% of their max current, using a simple ebay current limiting buck but ultimately would like to use them PWM in a way similar to the USE exposure Flare bike light.
I think I understand what PWM is and what it does but I haven’t a clue how to make it happen or what conditions it might require. For example, if I use PWM can I site the actual emmitter away from the controller or does distance cause a problem? Is there a usual way of accomplishing this or is every case different and specific? Would I use a PWM controller before or after the regulator or would one normally use an all in one reg/pwm device?
I was considering using perhaps an Arduino but wonder if something else would be more suitable. I have some (limitied) experience of compiling Arduino sketches but doubt I could author one from scratch at this stage.
“In my head” I’d envisioned having just the emitter and the heatsink mount to the mirror and run large enough AWG wiring to the controller (to carry the current without overheating) sited somewhere in the dash/fairing of the bike.
Any suggestions/slaps around the face before I cause chaos would be greatly appreciated.
Cheers
D
Can’t help you with the build but with XHP LEDs on max it’s like adding car headlights you could be too visible sure others will chime in to help you get a good safe output.
I like the idea of adding extra lighting to improve both yours and other drivers visibility of you. Just curious as to the reasoning behind using PWM to contol brightness vs. current limiting? Were you wanting to create that stroboscopic effect when driving to attract attention? I’m not sure how would achieve that (in this application) without the use of an arduino or other microcontroller. In my opinion, the buck driver would suit your needs just fine as the xhp50 is extremely bright and would definitely command attention, even at half its rated current. As far as the mounting goes, distance from the driver shouldn’t matter as long as a thick enough gauge wire is used, say 20awg or larger. How are you going to protect the led from the elements like rain, bugs, road debris, etc…?
Hi maddog7, welcome to BLF. At the risk of being a party spoiler I suggest you start by taking a good look at the Road Traffic Act and associated regulations. There are dozens of rules for every part, bolt and nut on a motor vehicle. IMHO the only lights allowed on handle-bars et cetera are direction indicators.
Yep- the UK and many other places are very explicit about lighting and enforce the rules strictly. However as of 2002 you could have a clothesline on your bike if it didn’t impair your vision. So much for rules and sanity
Hey all,
Many thanks for the replies and welcome!
My thinking on the flare sitaution would be something along the following lines.
Set up PWM at a particular duration and rest period to give about 75% max current and medium duty PWM (medium brightness), have this run for approximatley .2 sec followed by 75% current high duty PWM (high brightness) for .05 sec and repeat.
I believe this would satisfy the law as it applies to BICYCLES but need to do some further checking on motorcycles. In the UK a motorcycle is classed on the registration document as “Bicycle”. The law where it comes to pedal bikes seems to class them both as a “conveyance” and a “vehicle” so I’m hoping that things might apply interchangeably. I have a friend who is a traffic/collisions investigation cop so I’m going to ask his advice though I’m aware that not even the police are completely sure of all laws (believe it or not!)
I make the ass-umption that modern vehicles fitted with LED DRLs are controlled using PWM since many of them reduce their brightness when the corresponding indicator is used to make the orange LEDs of the indicator more visible. If this is the case then every such vehicle is actually using flashing (albeit at very high frequency) forward facing white lights.
The 2009 onward Honda Fireblade has LEDs in the edges of its mirrors in exactly the way I intend using them.
I’m not attempting justify my position with what I’ve said above, perhaps more to stimulate some debate and illustrate some of the confusion. I suspect the cops would not be too worried unless there was an accident (the very thing I’m attempting to avoid!)
Construction wise it was my intention to use a thermal pad to adhere the emitter to a heatsink and make an aluminum ring with an inside chamfer to control the direction of the light, then after all is constructed use clear casting resin to fill it all in. This would make it effectively a sealed disposable unit but since the material cost is only about 15 eur, its not a worry.
Hi tru3s1lv3r,
Thank you for that
Yeah, pretty much all of your presumptions were the way I was looking at going. I assumed PWM would be necessary to produce the flaring effect and did wonder if an arduino would be necessary. The USE lamp manages to accomplish this using just a tiny driver, I did even think about buying a couple of the USE units and robbing the drivers. I also made the assumption that if PWM was used the effective current is lower and would not heat the wires so readily though I still intended to use about 20 AWG wiring.
Ah, I understand. To save from having to use an Arduino module, they are probably using a chip like an attiny13a or even an attiny25/45/85. These little chips can be programmed the same way as an Arduino and are much much smaller. You will have to make your own pcb, though, and that will increase cost and complexity. As far as the wiring, I don’t think you’ll have any heat issues with 20awg as it should be good to 11amps.
Ahh,
Cool!
That little attiny series thingy looks very promising, I did wonder if such a device existed in this realm and the attiny would appear to be it!!
I can probably make my own PCBs if i do some homework (I have a CNC mill) The only thing I’m lacking in that situation is brains!!
I’ll have a look at that!
Many thanks again!
There’s a driver available HERE that can be used for what you’re doing. Get the BLF A6 firmware, and you’ll have a bike strobe available just like you’re looking for. The firmware has other modes, too, but you don’t have to use them.
You will have to have a zener diode installed to protect the MCU (the attiny chip) from overvoltage. This is called a zener mod. I don’t see that as an option on this driver’s page, but if you contact the owner, he may be willing to do it for you. I know he has offered it on other drivers in the past. At the least, he could tell you how it’s done and sell you the components to do it. There is plenty of information here about zener mods as well. Use the search box at the top left of the page to find any information you need (about drivers, firmware, zener mods, emitter choice, etc.).
If you’re comfortable flashing the MCU yourself, you could download the BLF A6 firmware and eliminate all the modes except the bike strobe, and flash it to the driver that way, so there will never be any confusion while in use. (mystery mode changes and such)
sure others will chime in to help you get a good safe output.