My first bike light project.

[mr_marmalade]

Hi everyone, I've been looking into making a DIY set of bike lights for a wee while now & am almost done getting the bits together. My design is based on the following one that I'm sure you all know of;

http://myfwyc.org/bikeled/DIY_LED_Bike_Lighting_Guide.html

But, I was unable to get square section tubing so am trying to do a similar thing with right-angle section lenghts. The annoying thing is that they aren't perfectly 90deg, more like 88-89 so it is making the alignment a bit off & I'll have to work around this. See my skecth;

Its a slow build but I've just mounted the 3 CREE Q5s onto the aluminium face and got the two aluminium angles stuck together to make the upper section. My concern at the moment is about the battery as I'm using a 3700mAh 12v one and a 3023 BuckPuck @ 700mA. Can someone confirm if this is a decent enough setup, well its kinda too late now I've stuck the CREEs on... hmm. Thoughts/opinions anyway would be welcome! Thanks.

I'm kinda hoping this project goes well as I want to make my brothers sets for Christmas presents so we can ride in the dark! I'm keeping it simple with the 3023 BuckPuck but am already wishing I'd got a variable current one as I'm scared that the 700mA one will just cut out when the juice* runs out (*that's a technical term).

 

[znomit]

Looks great! Should have good runtime with that battery too (4hrs plus)!
I would leave out the heatsinks on top, see how hot it runs...you can always add them on later.
Variable brightness is always a good idea, this thing will blind oncoming traffic!
What lenses? 2 spots and a flood?

 

[mr_marmalade]

Hi thanks for the reply, sorry about my delay in response (was expecting email notifications)! I've just made up two heatsink sections, oh well I think they'll help structurally as their outer sides will glue to the inside sides of the two L-bits that form the lower section

Thanks for the response about the battery, i was afraid i'd be a few volts under ideal as all the other threads i see use a 14v battery but i couldn't find one here in the UK & i was keen on using an RC battery pack for simplicity, best i could find was 12v.

Lenses I'm using are [FONT=arial,geneva]one Ledil CRS-RS ±6° & two [/FONT][FONT=arial,geneva]Ledil CRS-M ±14°. But... I'm thinking/hoping that I can sit the lenses in without removing the adhevis backing so that they sit loose & are held in sufficiently by the perspex at the front. Not sure about that though in terms of waterproofing as might get a gap around the middle due to flex.

If all goes well I'll try making a bar mounted one. But I'd better not get ahead of myself & finish this one first!

Something I though might interest people;

http://www.rapidonline.com/producti...ive+Bondline++200+thermal+pads&moduleno=78532

I got the squares as are more material for my £££s and can cut to achieve more than ten per strip. Anyone used this sort of thing? I've got Arctic Silver Adhesive from a few years ago but one half of the compound was almost solid but managed to get some from the other end of the syring by opening it up & i used some for the '2*L into a T' top section, but am wanting to save it as its expensive stuff.


Thanks!:sick2:[/FONT]

 

[znomit]

Your battery at 12v is probably just sufficent to power things, 11V for the LEDs and maybe 1v for the 3023??. Depending on what sort it is the voltage may drop significantly under load or as it drains so you may see reduced output over time... Have you bench tested it?

Lenses sound good.
Make sure all the gaps are sealed up (silicone is great) and watertight.

Be sure to post beamshots and final pictures!

 

[mr_marmalade]

What is the best, recommended plastic to use for the lens at the front? Polycarbonate, perspex? Any 'best' one, i.e. good scratch resistance? The light is coming along nicely. Pics eventually, once I've finished it.

 

[mr_marmalade]

Hi all, sorry it's been a while since my last post but here's how my lights have turned out so far. They're nearly done, I'm trying to get 5mm acrylic for the front as the front flexes too much hence not waterproof as would like and i'm trying to make a better mount as the one in the pics was a whack-it-on velcro effort; works but hope to make something better.

Front;

Rear;

Guts;

Mounted;

For many more pics & a few design dead-ends see;
http://smg.photobucket.com/albums/v643/visual_etc/DIY Bike LED Lights/

I'm currently seeing how long the battery will last, on the first charge it has been on for a bit over 4hrs and still going. Is fairly hot (velcro currently isnt helping heat dissipation either). You can see how I've deviated from the original design a bit, reasons being that drilling the plastic was a nighmare so a slotted design was finally reached, and is simpler too.

What do you think?

 

[znomit]

Looks tidy!
Are there rubber seals on the front and rear faces? You might want to replace them with thermal adhesive so the front and back can help with cooling.

With the front cover, I just use mylar (clear overhad projector sheets from the bookstore) and silicone adhesive.

If the screws went all the way through you could mount/hook the velcro onto them, keeping the top cooling fins clear.

 

[mr_marmalade]

Thanks, yep they are rubber seals. I don't want to glue the lens on as i have purposefully left it so that i can switch lenses and could then replace the plasic easily if it got scratched. i can't use the bolts as mounts for the velcro as the side angled bits are glued on and not strong enough. i was originally (EDIT: not originally, more a mid-design) planning on having one set of the legs extending downwards but still ended up breaking them off too easily; finally have single-purpose end mounts. still working on a better mount, wont be as nice & simple as the velcro method shown though, but its is pretty rubbish & ruins heat dissipation.


why would i want to moung the plastic with a thermal adhesive? plastic doesnt have good thermal properties, i think! the rear place i'd just rather have weather-sealed than heat considerate as there aught to be plenty aluminium on the rest of the body. i've just put a room thermometer above (bulb at about 1cm distance) the light body and it reads as...

eh, its relatively cool to the touch now, its was pretty hot earlier on. what's going on? it's barely warm now whereas before its was too hot to hold for very long. i've had it on in my room for 5.5hrs now. all the led's are still on. is it less bright now - i'm not sure. i thought the driver was meant to keep it at a particular brighless level/voltage and then go off suddenly? or am i seeing it decrease gradually?

 

[Brum]

The battery probably won't be sufficient. It will work, but it won't keep the LEDs in regulation during the full runtime of the batterypack, certainly if you are running it @ 1 amp.
When the battery is running down (you can go to 1V/cell, or even lower), the voltage will drop to 10V, the Buckpuck itself wants an additional 1V (or a bit more), leaving you with 9V while 3 XR-E's in series @1000mA will probably need around 11V (+/-).
This examply is around the end of the runtime, but with 2V of difference between Vin and Vf, you can imagine it not being an ideal setup.
The best solution for this pack would be an buck-boost driver, but these are pretty hard to find if you want a fully build driver (the buck-boost driver chips are pretty easy to get).

About the lenses, I've tried the CRS-RS (and all the other lenses LEDIL makes..), but I find them way too spotty.
Producing color separation and a lot of artifacts, including the projection of the bond wires on the LED chip. And it's beam pattern is square...
I like the SS and above (D,M,W) a lot more, producing a nice evenly spread beam.

Liking your design btw!

 

[mr_marmalade]

Its a 700mA driver, does that change anything, i.e. make it ok? well i doubt it as its the voltage that the driver is regulating to my understanding. i did ask about the battery some time ago too. if i could get a 14.4v one i would have but cant find one. i may then make a 2 LED handlebar mounted light and relegate it to that, if i can get a 14.4v R/C pack, but my charger is a 10 cell max. one, d'oh! :mecry:hmm, maybe i'll just have to get some sort of boost thing like you mentioned. any links, something as easy to fit as the current one would be nice?

i havent tried the light on the trails yet, but i'll just make do with the type i've got as i like them being square, a bit like me. :naughty: the two diffuse ones dont appear noticably square at all, only the spot one at close distance, but i'm not bothered by that, yuet anyway. i've nothing to compare it with anyway.

thanks Brum, i'm quite chuffed with the design myself! i'm trying to make a similarly neat helmet mount.

 

[mr_marmalade]

Ok, the battery is currently at 11v after 6.5hrs constant running and it's still on. i might look into getting a small 4cell pack and run it in series with my current one to save relegating any parts and to have more volts to play with. i saw some connector to do this somewhere online, must try to find it again. i didn't quite understand what you said Brum or you didnt answer a bit of my question - how should a light like mine actually behave in terms of dimming/running out of juice? i though it would be a sudden-off rather than a slow dimming death? :sick2:

 

[znomit]

Try it on the bike or in front of a fan to see what the cooling is really like. It shouldn't be more than warm.

For the mylar I was meaning to cover the lenses. Its cheap and easily replacable, use clear silicone like for a fishtank and it will be watertight.

 

[mr_marmalade]

instead of the bike inner-tube rubber seals you mean? or instead of the acrylic entirely? i cant glue straight onto the lenses because they aren't glued in themselves, they'd just fall out. I never removed the cover on the rear sticky pad; i wanted them to be easily 'on the trail' interchangeable. there isn't enough surface to silicone glue the lens on and i wouldnt want to cover the lenses with glue really. i found some thicker (hence less flexible) reasonably-priced sheets on eBay, but am somewhat loath to use eBay.

i'm not hugely concerned with the heat as its not blown up or melted and still seams to be working, i might leave the fins a bit bigger next time though. outdoors i'd expect it to be less of an issue considering its freezing here in the east of Scotland at this time of year! its more the fact that it used to be fairly hot, and now its not? why? is this just due to the battery running out... but i thought it would go off suddenly rather than dim as it drains. this thinking being due to reading the likes of this;

http://www.gearreview.com/2007_led_lights.php

7.5hrs running now an the lights are still on...

and thanks for all the replies, i will be heading to bed soon though.

 

[znomit]

At best you should be seeing about 5 hrs from that battery(probably a lot less though). At 7.5 hrs there wont be much juice left so you are actually running the LEDs much lower than 700mA, hence they aren't so hot. Yes even at 200mA they will look bright. Probably not too good for your battery though.

I was meaning on the outside of the front face (instead of the acrylic entirely) to run a small bead of silicone around and stick the mylar on. That would make it impossible to change lenses mid ride though.

 

[Brum]

The slowly dimming thing is what I meant with 'no regulation'.
After a while (2 hours max I'd say) the battery cant supply the voltage to keep the LEDs @700mA. In essence, from here on the LEDs go into direct drive.

With a better battery (14,4V), the LEDs stay in regulation throughout the entire battery life (depleted @ 12V which is still above the Vf, if you keep the 1-1,5V for the driver in mind, a higher voltage battery might even be better).
And it will cutoff pretty promptly when the battery is completely depleted.

 

[mr_marmalade]

Righto, thanks for the replies. I shall look into getting another battery in series with the existing one, smallest suitable one I can see is 4.8v, so it'll end up being 12v + 4.8v = 16.8v, that should do the trick! More volts simple means more running time though doesn't it? I might add a 6v pack then as its the same length as my current battery, doesnt cost much more than the 4.8v one, but I end up with an 18v beast!

:devil:

I hope that isn't too much? It'd last ages too!

Now for more meddling with aluminium to make some sort of better helmet mount.

 

[aljsk8]

my setup does the same as this - 1hour regulated then slow dimming - it goes into direct drive for ages - first few hours are very reasonable though - so i just live with it

Alex

 

[mr_marmalade]

Ok, but I'll run them as they are to begin with but will look to get another battery, have just made a series connector for them.

Another question though; what are the merits of adding loads more volts, say beyond 14.4v? Will having an 18v for example battery at 3700mAh run longer than a 14.4v 3700mAh battery. I'm asking so that I don't go buying a higher voltage dual-battery setup when it wouldn't be any better than a lower voltage one.

Thanks again.

 

[znomit]

For run times you multiply your volts and amp hours for the battery and divide by those of the light.
So you have 3.7Ah x 12v = 44.4 for the battery.
LEDs are drawing 3.5v x 3 and 0.7A = 7.35
44.4/7.3 = 6hrs
Now take off 20% for the efficiency of your driver = 4.8hrs
Take off another 10-20% at least because batteries are hardly ever as good as they claim...around 4hrs.
Run times will be longer if you are in direct drive (but light will be dimmer).

Adding more volts extends run times because your driver draws fewer amps at higher voltage. So going from 14.4 to 18 is 25% more volts so also 25% more runtime (or you could use a 18v 3000mAh pack for the same runtime). Approximate because your driver efficiency will change with voltage. Checks the specs.

 

[JB01245]

Here is a nice little program that you can change the variables on and see the result.

LED Pro
http://www.jtice.com/led_pro/led_pro.htm