DIY: the AK47 of Bicycle Headlights

[crimsonhalo]

OK, I'm new here. The man at my neighbourhood bike shop wanted $350 for a a 200 lumen headlight with Li-ion battery, and the construction frankly sucked not to mention the dust in our climate would kill it fairly quick. I've made lights for my bike and trailer in the past, usually using 10,000mcd white and red LEDs bought on the cheap from eBay, but what I want to do now is design a respectable headlamp for the bike itself. I started a 50-LED rectangular array of 5mm LEDs tonight, but I didn't feel satisfied ...

I was wondering if anyone can offer insights on the current crop of LEDs out there, for a design I'm considering for this headlamp. Basically, it will end up as the AK47 of headlights, not cutting edge perhaps, but rugged and versatile and reliable enough that it can be depended on in a variety of terrains and climates. I intend to open-source the design and publish via WWW for other cyclists to build and improve on the design in turn.

Goals:
- LED headlight
- $50 parts budget. Scary, but recession friendly.
- Road and trail capable
- Wet and sandy/dusty terrain tolerances
- Illumination: not sure about numbers but must cover a sufficient area to ride safely at night
- Passive components if possible, otherwise minimal circuitry and rugged
- AA size NiMH or NiCd cells, since this cell is the AK47 round of flashlights IMHO and using an even number of them in any circuit is good (I can't tell you how irritating it is to keep track of rechargeables on a 3xAAA lamp, grrrrr)
- Runtime: 2 hrs minimum as target
- Able to take apart using a swiss army knife, if compartments or covers
- Build time of roughly an afternoon

Basically, the circuit is what has me stumped because I've been out of the loop so long, and am only getting back into electronics recently, so I have hardly any clue what may be out there. From the look of eBay, many new generations of products have come out these past few years. I welcome ideas and suggestions on what lamp might be best for a bike headlight. The simpler the better. Heatsinks are an option if needed but lathes are right out.

I have stuff -- tools, NIMH and NICD batteries, battery holders, various electronics bits, and some 2x4 inch aluminum heat sinks salvaged from a PC monitor -- on hand as I speak, and will be looking to test stuff out as the design moves along.

I was also very inspired by this group's 6000 lumen build with what looks like a 9.6 volt battery and a large aluminum block heatsink. Something like that design with 400 degree clear silicone as the shock buffer, was along the lines of my first thoughts.

Also, eBay: I know from experience some things there are great and others are crap, though I want to poll a wider audience here. What have you bought there that's satisfying in terms of LED flashlight tech? Any good "parts flashlights"? Any ready-to-go devices that you simply wire up to a battery? Any circuit dealers that this group prefers?

Many thanks for your time and interest.


~ Brian

www.crimsonhalo.com

 

[Tidra]

o.k.

keep on dreaming,...

let me know when you find something like that,...

there is a lot more, than just that what your goal is:
- what about some different output powers
- weight
- how to mount
- how big and heavy would the battery pack be

otherwise the ultimate solution in price performance would be

http://www.dealextreme.com/details.dx/sku.30864

there are a lot of cons and pros, but from my point of view that's about it...

you can buy some PT EOS or PETZEL product, and I know some people who really ride in the woods whit those lights,...

but if you would like to ride a bike on the trail in the wood you need at least 500lum or more,...

I use to ride a bike with 700lum and I was quite happy with that, but now I ride a 2700lum and I am still not satisfied, because I will drop back to around 1500lum and better optic,..

 

[rayman]

Surely you could go with a self-made bicycle headlight for around 50$ as you already have some stuff and craftman-skills judging from your post. But it wouldn't win a beauty competition .

You could buy a P7, reflector and lens from DX and a driver from KD. All together that would be about 33$. Then you just have to glue the P7 to the heatsink and put the reflector and lens on it. I would recommend you to seal it. Maybe use some pipe or something for protection. After that connect the P7 to the driver and the driver to the battery. And of course solder a switch in the curcuit. That would be one cheap possibility. Dust won't be a problem if you seal everthing appropriate.

BUT...I wouldn't save money on the driver. I used two of this drivers and the both had failures.

rayman

 

[chelboed]

First of OP...gotta dump those little low powered LED's. Move into the new genre of hi powered leds.

Go to Dealextreme.com and order a Seoul SSC P7 LED and 2x of the single mode 3.7v / 1.4amp 17mm driver boards. Also...grab a pr of Trustfire 2500mAh 18650 batteries. This all should total about $27 USD with free shipping.

Then...go buy a Ledil Boom reflector for $5-$10.

Go to flashlightlens.com and get the apporpriate size lens to cover / retain the reflector.


Then get yourself a piece of aluminum Hex bar that's 1.25" across x 2" long. Using a drill press, drill bit, and end mill...drill the end of the hex to depth to fit the LED, reflector, and lens. Then make a face cap to retain it all. Drill and tap.


Bore an 18mm hole in the back. Solder the two 17mm circuit boards in series to run 2.8 amps to the emitter. Make a small tailcap to retain it.

Fin the body with the end mill or a dremel.

Blah, blah, blah...wire it up (you'll need to drill holes)



Obviously this is getting complicated, but you get the picture.




Another option is to get an MTE SSC P7 2-mode flashlight from dealextreme. Cut the body off it with enough of a stub to grab onto with some scope rings or a flashlight mount. Get a cable gland from batteryspace.com. Round off the corners of the big nut using a sander. Press-fit the cable gland into the stub left over.

 

[crimsonhalo]

http://www.dealextreme.com/details.dx/sku.30864 >> That looked similar to the one the guy at the store was trying to push for $350... difference being yours throws off 900lm, not 200, and can actually justify its price of $80. Worth bookmarking, but better for a day when I have serious cash to throw at a project. I'm going for a lower-midrange sort of thing I suppose.

As for weight? Aluminum. 85% of my custom trailer is made of it, and I barely feel a difference when I hook up to haul. A couple pounds for a light system is no issue but the shape needs to be practical so I'm using six AA cells in three plastic battery holders inside of an aluminum case that will be affixed to the frame. Will be going junkyarding soon to find suitable stock pieces.

Light-wise, has anyone had much luck with the 5 watt Crees and Luxeons from places like DX and eBay? Do they work as advertised? I'm also seeing a lot of flashlights at both places that bill themselves at ranges of hundreds of lumens which run a 5W Cree or Luxeon inside.

For the moment I'm considering one option as buying a trio of parts flashlights off eBay since they have LEDs/reflectors and casing included, get a decent driver, and compromise.

I'll probably try a few designs of different concepts to see what can be done ...

 

[crimsonhalo]

[But it wouldn't win a beauty competition]

Hahaha ... that much is true, but in this case it's the function. I had lights before that got killed by rain, or dust, and various stuff I owned got killed by the dust or sand out here too. It's a bit of a tradeoff, I guess at least I have a good test environment to work in.

I used to night ride with two 16-LED lamps, made from 10000mcd LEDs off eBay, and it worked all right. The circuit was simple, the array was like the one here: http://cgi.ebay.ca/Super-Bright-53-...tem&pt=LH_DefaultDomain_0&hash=item518c879e72 ... difference was mine ran on 8 AAs, and was made of ABS and copper. I used plumbing parts, and it was as ugly as it sounds!

The arrayed set I was putting together last night will be used as one of the new designs, but with a nice exterior. Aluminum most likely.

The other design may go with a handful of better-quality LEDs powered at a higher current like the ones you mentioned. The nice thing is the price has dropped so much since last I looked. For somewhere in the area of $40-45 it looks like it may be feasible to run a pair of 5W units on a decent driver board. Am I on the right track?

 

[John_Galt]

I'd say poke around the MTBR forums for some of their home meade lights made out of square aluminum tubing.

I'd say go with two Cree XR-E's, and one spot and one flood optic (about 8* and 40*, repectively). A cheap two or three mode driver should be easy to find on DX. Look for one with your input voltage, output voltage, and small size (15-18mm in diameter).

If you ran your flood at 700mA, and the spot at 1A (this would probably require two drivers) you'd have a good bright light, and still get decent runtime with your battery setup.

 

[crimsonhalo]

I had a hunch it would be possible to break 500lm without breaking $50. I'm good with higher power especially on night riding, and I didn't realize the P7 was 12 watts (finally found an entry that mentions that).

I definitely want NIMH (or even NICD in a pinch) for the easy maintenance and versatility, plus I have a stock, and I plan to add a solar charger in the future and anyone I spoke to that knows Li-Ion warned against using them for applications like these. Apparently, they're very fussy and don't cope well with deep cycling.

That said, does DX provide specs anywhere about these boards? I'm curious what the acceptable voltage range for these drivers is. It's a good starting point; thanks.


~ Brian

First of OP...gotta dump those little low powered LED's. Move into the new genre of hi powered leds.

Go to Dealextreme.com and order a Seoul SSC P7 LED and 2x of the single mode 3.7v / 1.4amp 17mm driver boards. Also...grab a pr of Trustfire 2500mAh 18650 batteries. This all should total about $27 USD with free shipping.

Then...go buy a Ledil Boom reflector for $5-$10.

Go to flashlightlens.com and get the apporpriate size lens to cover / retain the reflector.


Then get yourself a piece of aluminum Hex bar that's 1.25" across x 2" long. Using a drill press, drill bit, and end mill...drill the end of the hex to depth to fit the LED, reflector, and lens. Then make a face cap to retain it all. Drill and tap.


Bore an 18mm hole in the back. Solder the two 17mm circuit boards in series to run 2.8 amps to the emitter. Make a small tailcap to retain it.

Fin the body with the end mill or a dremel.

Blah, blah, blah...wire it up (you'll need to drill holes)



Obviously this is getting complicated, but you get the picture.




Another option is to get an MTE SSC P7 2-mode flashlight from dealextreme. Cut the body off it with enough of a stub to grab onto with some scope rings or a flashlight mount. Get a cable gland from batteryspace.com. Round off the corners of the big nut using a sander. Press-fit the cable gland into the stub left over.

 

[chelboed]

I think people are a little too scared of LiIon batteries. I use "protected" cells with this light. When they reach the minimum threshold...they just shut off. (3.5hrs) If they reach the max threshold in the charger...they stop taking the charge. (my charger is also a Pila IBC smart charger...so there's "extra protection" there that's really not needed)

LiIon's are amazing...and easy to use if you have protected cells.

I actually bought two DX drivers from hoffmanamps.com and soldered them in series for a full 2.8amps to the P7...giving me ~750lm. The stock driver in the light is probably only pushing the P7 to ~ 500lm.

Sticking with NIMH is not terrible, but a comparable pack is tremendously biggah. I was a little leary of the LiIon's until I researched them a bit more. Now I'm not worried.

You could also just buy a pre-made pack and plug'n'play charger from Batteryspace.com if you're concerned about building one.


As far as these boards are concerned...

Heck man...just buy this P7 drop-in and build your housing around it. Make sure to get good thermal contact to move some heat:

- Aluminum Textured/OP reflector construction
- Features a SSC-P7-CSXO LED emitter
- Voltage input: 2.7~4.2V, maximum accepted 4.2V
- 2500mA current output measured at LED (manufacturer rated)
- 5-mode driver circuitry: Hi 2500mA 900-Lumen > Lo 1000mA 300-Lumen > Fast Strobe 2500mA 600-Lumen
- Diameter at bezel edge: 26.5mm
- Height without support spring: 28.1mm
- Height with support spring: 35.4mm
- Able to use 1*18650 / 1*17670 2400mAh battery


My only issue with this is that I trust my own soldering and construction much more than a cheap Chinese construction.

I had a hunch it would be possible to break 500lm without breaking $50. I'm good with higher power especially on night riding, and I didn't realize the P7 was 12 watts (finally found an entry that mentions that).

I definitely want NIMH (or even NICD in a pinch) for the easy maintenance and versatility, plus I have a stock, and I plan to add a solar charger in the future and anyone I spoke to that knows Li-Ion warned against using them for applications like these. Apparently, they're very fussy and don't cope well with deep cycling.

That said, does DX provide specs anywhere about these boards? I'm curious what the acceptable voltage range for these drivers is. It's a good starting point; thanks.


~ Brian

 

[crimsonhalo]

When it comes to Li-Ion do those 'protected' cell carry overcharge protection in a non-smart charger? The recipe I'm going for is something that lets the hardware do the magic and frees the user to do whatever the lamp is there to help them do better.

Why people are afraid of lithium, LIPO or LI-ION, is because the stuff exploding in iPods, laptops, and phones are of these types and apparently companies don't like telling people how many are others had the same thing happen to them. People start networking, and the whole thing blows up in everyone's faces (pardon the pun).

Apple: http://www.guardian.co.uk/technology/blog/2009/jul/23/apple-ipod-overheating ... also, Dell: http://www.reghardware.co.uk/2006/07/21/overheating_laptops/ and Nokia: http://www.theregister.co.uk/2005/03/14/nokia_thailand_handset/

In a nutshell, this was why the public became leery. I've seen demos myself on how easy it is to cause runaway chemical reactions. It's to the manufacturers' great discredit that stuff like this is even happening (bad QC? No cell protection?) and the mfrs go on to shoot themselves in the foot by pretending it's not happening, creating even more distrust.

I've had mixed results buying cells online, twice I got taken by eBay sellers dealing in fakes. One had AA NIMH at a low price, turns out they were faking it by taking smaller (AAA?) cells and putting them in cardboard and metal clad cases to look just like your standard green no-name NIMH (side markings: BTY / 2200MAH".

I caught on after finding that one developed a rattle whenever it was flipped over, and none of them took a charge after the first month of use. The other situation was different, it was real AAAs but they died permanently when stored on the shelf for a couple of months and could not be revived with charging.

Naturally, I expect this project to result in mail-order, so to anyone reading this, feel free to throw me the names of your favourite battery sources and I'll be grateful. I'm new to the DealExtreme scene and still getting a feel for how they deal with feedback, reputations, manufacturers, and such. Their prices in many areas also look better than eBay.

As for LEDs, five years was worth it, even the most conservative kit you guys have put forward sounds seems to vastly outperform the lights sold commercially here at the bike stores. The price goal seems to be met, now on to the game of matching parts to parts ...

A few other questions:

Adhesives: I've heard about the use of JB Weld, quick set epoxy, and thermal epoxy. What have others here found work best for them?

Drop-ins: I tried finding a thread about these, they're few and far between and I couldn't find any that dealt with MCE and P7 type LEDs. Do such units have enough heat sinking by themselves to be useful? Or, as I suspect, is it better for the performance and life of the LED to haul out a copper block, drill a hole, and go about extending the heatsink?

As for modes, ON-OFF in tandem with a control pot is what I want, it makes more sense in terms of having speedy control over things. I don't want strobe mode, this layout already sounds plenty visible for the road.

That way I can also go on to make a LED head that's waterproofed/dustproofed with a glass lens in front, and further along I'll set up a control pot in its own protective housing with similar protections hopefully, on a mount for the handlebars.

~ Brian

I think people are a little too scared of LiIon batteries. I use "protected" cells with this light. When they reach the minimum threshold...they just shut off. (3.5hrs) If they reach the max threshold in the charger...they stop taking the charge. (my charger is also a Pila IBC smart charger...so there's "extra protection" there that's really not needed)

LiIon's are amazing...and easy to use if you have protected cells.

I actually bought two DX drivers from hoffmanamps.com and soldered them in series for a full 2.8amps to the P7...giving me ~750lm. The stock driver in the light is probably only pushing the P7 to ~ 500lm.

Sticking with NIMH is not terrible, but a comparable pack is tremendously biggah. I was a little leary of the LiIon's until I researched them a bit more. Now I'm not worried.

You could also just buy a pre-made pack and plug'n'play charger from Batteryspace.com if you're concerned about building one.


As far as these boards are concerned...

Heck man...just buy this P7 drop-in and build your housing around it. Make sure to get good thermal contact to move some heat:

- Aluminum Textured/OP reflector construction
- Features a SSC-P7-CSXO LED emitter
- Voltage input: 2.7~4.2V, maximum accepted 4.2V
- 2500mA current output measured at LED (manufacturer rated)
- 5-mode driver circuitry: Hi 2500mA 900-Lumen > Lo 1000mA 300-Lumen > Fast Strobe 2500mA 600-Lumen
- Diameter at bezel edge: 26.5mm
- Height without support spring: 28.1mm
- Height with support spring: 35.4mm
- Able to use 1*18650 / 1*17670 2400mAh battery


My only issue with this is that I trust my own soldering and construction much more than a cheap Chinese construction.

 

[crimsonhalo]

You know, I just recalled while mulling things over that 900 lumens is a bit over half the output of a 100 watt incandescent bulb. That should be plenty. Do the P7 type LEDs throw off a lot of heat? I'm using glass lensing, but I was curious about whether I needed to consider possible thermal shock from incoming rain/snow.

Considering it's all aimed forwards, 900 lumens looks a good goal to strive for. I appreciate the suggestions and help thus far; are there any other nice LED/reflector combos that reach around this output?

I had two thoughts for final design in mind:

- single head

or

- over-under where one provides flood and a second provides spot

Lights would be on in unison in the second case, no need of separate controls or wiring. At this stage considering the average joe knows what switches are but not necessarily what resistors are, I would tend toward waterproof switching in the final design, but possibly would include a pot on the one I make myself. Do they make things that can handle the nearly 3 amps you mentioned?


~ Brian

 

[crimsonhalo]

What also caught my eye:

http://www.acriche.com/en/product/prd/zpowerLEDp7.asp

Manufacturer's engineering guides for the Seoul P7 specifically warn users AGAINST any form of pulsewidth modulating drive circuits in cases where high illumination is needed, because it reduces output. They say instead that you must set it up with a correct resistor to control input voltage (charts and datasheets linked above).

What's the verdict? I've been searching here and seen no mention so far of this issue! They mention the heating which some have noted as causing a dip in luminous intensity when the heat sink heats up. Perhaps given a big enough heat sink this would not be an issue?

~ Brian

 

[AnAppleSnail]

Technically speaking, an LED is less efficient at higher current. So if it's running at 1 amp half the time, it'll be less efficient than running at a half amp constantly. Maybe that's it? I don't know SSC LEDs very well.

 

[crimsonhalo]

That's what I was wondering as well.

Technically speaking, an LED is less efficient at higher current. So if it's running at 1 amp half the time, it'll be less efficient than running at a half amp constantly. Maybe that's it? I don't know SSC LEDs very well.

 

[BrianMc]

What also caught my eye:

http://www.acriche.com/en/product/prd/zpowerLEDp7.asp

Manufacturer's engineering guides for the Seoul P7 specifically warn users AGAINST any form of pulsewidth modulating drive circuits in cases where high illumination is needed, because it reduces output.
~ Brian

The biggest resistance to heat movement is in the LED itself form the Junction to the contact pad, so a larger heat sink will help minimally. If I remember the lumens/wat bersus current for this LED correctly, its efficacy drops rapidly at higher currents. So it is much better in light output per watt input and so in heat generated to run it all the time at 50% current than to use 100% current in a fast on/off cycling. This doesn't meant hat all current regulating drivers are out, but resistors as voltage limiters may be an acceptable alternative to get lower current through the LED. The output will drop some as the battery discharges, of course.