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Some thoughts on bike light design and user interfaces

 
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oh_blinding_light



Joined: 15 Oct 2008
Posts: 240
Location: People's Republic of Rosendale

PostPosted: Tue Oct 06, 2009 12:51 pm    Post subject: Some thoughts on bike light design and user interfaces Reply with quote

A few FATs members have previewed my latest bike light design. To answer some of their questions, I figured it'd be easier for me to just SPAM the technical forum with some documentation I wrote for the light.

Some thoughts on a High Powered LED Bike Light and it's user interface

The BFL-1000 is high intensity LED driven by a current controlled buck converter. The buck converter is controlled by a small 8 pin microcontroller. Software programmed into the microcontroller determines the user interface for the light and handles tasks such as warning the user when the light becomes too hot, or the battery is getting low.

The LED used in the light is a CREE MCE. It draws about 10 watts of power and produces between 600 and 700 lumens of light. This is roughly 2.5 times the efficiency of a halogen bulb and maybe a few percent more efficient than a HID bulb. Because LEDs can be switched on and off very quickly (a process known as pulse width modulation, or pwm), they can be made to appear dimmer by varying the percentage of time the light is really on for. This happens at such a high frequency (several thousand times a second), that you will never notice it. The advantage to dimming a light this way, is you draw less power and can extend your battery life. If you run a LED light at half brightness, you get roughly twice the run time from your battery. Note: it is not possible to dim HID lights, but you can do pwm dimming with a halogen light

Some of you will ask, what's a lumen? It's a measure of the total amount of light produced by a light source. It is kind of subjective, because it takes into account how bright a light source looks to a person, and the human eye is more sensitive to some colors than others. A couple of examples: a household 60 watt light bulb produces about 800 lumens, a 20 watt mr-11 halogen light bulb produces around 400 lumens.

Power sources:

The BFL-1000 is designed to operate from any voltage source producing between 8 and 24 volts that is capable of producing enough current (more on that later). Below 8 volts, the light will still operate, but will begin to dim. The buck converter allows the light to produce about the same brightness from any voltage source that meets the above requirements. For practical purposes the lowest voltage battery I'd recommend is a 9.6 volt NiMh (or NiCad) battery. NiMh batteries are pretty cheaply available in an AA cell format. 8 of these will produce a nominal voltage of 9.6 volts. A decent modern NiMh AA cell can produce between 1.8 and 2.7 amperes of current (or amps).

A quick approximation for figuring the run time of a battery is to multiply the battery voltage by the current it can produce to obtain the watts it can deliver (a watt is 1 volt times 1 amp, or to be more precise, a 1 volt battery delivering 1 amp of current for 1 hour, has produced 1 watt of power). Our 9.6 volt NiMh battery made from AA cells can probably produce around 20 to 25 watts. If we run our 10 watt LED light at full power, we'll get around 2 to 2.5 hours of light. I usually multiply that number by 80% to allow for batteries not being rated correctly by the manufacturer, batteries not being fully charged, etc.

The BFL-1000 can also run from a variety of LiIon (lithium ion) batteries. Some people prefer LiIon batteries because they weigh a bit less than NiMh, and should hold a charge for longer. They do cost more, typically a lot more. They need a special charger (never, never attempt to use a NiMh charger with a LiIon battery). They also can be a safety hazard. They have been know to spontaneously burst into flames.

Which battery type is better?

You will find some LiIon batteries available for quite cheap prices from a few Chinese importers. In my experience, you should treat these cheap batteries with caution. I've had a couple just suddenly stop working. I don't know if this is typical, but they failed in an open state. One cell in a pack of 4 wired in series suddenly died and the whole pack stopped working. This might have sucked if I had been hurtling downhill at the time.

More expensive LiIon batteries will have some kind of protection built in. This protection circuit will prevent the battery from being over charged or over discharged. It also will typically act as a fuse to prevent problems if a battery is accidentally shorted. You should always use batteries that have a protection circuit built in. One possible downside to this, is the protection circuit could shut off the battery while you are using it. This is one of the reasons the BFL-1000 has a low battery warning feature.

Of the 5 LiPo (Lithium Polymer) batteries I own, I've had one exhibit signs of internal overpressure. This typically happens if you have over discharged a battery and then tried to charge it again. Lithium Polymer batteries are mostly used in radio controlled aircraft, where you want a light high powered battery, that won't suddenly stop working. These have NO safety circuit built in, use with extreme care. I have seen some LiPo battery packs that do come with a protection circuit, these are usually not sold in the RC aircraft market, and are more expensive.

NiMh batteries have their problems as well. They don't do well if discharged too deeply. A good rule of thumb is never run a 1.2 volt NiMh cell below about .7 volts. For an 8 cell pack, never run the pack below 5.6 volts. A more conservative rule, would be never run the pack below 8 volts.

NiMh batteries don't like to be overcharged. Don't cheap out on the type of charger you use with your NiMh batteries. A "smart" charger will charge the batteries till it sees a slight bump in the battery voltage. Most cheap chargers will just start a timer when a battery is plugged into them. This can overcharge the battery if it was not fully drained beforehand. One sign of a cheap charger is if a nearly fully charged battery is plugged into it, it will heat up the pack (it will become very warm to the touch, a bit of warmth is OK), and not shut off. A smart charger, will try to charge a fully charged battery for a few minutes (an hour at most), and then shut off.

NiMh batteries exhibit a problem known as self-discharge. Just left sitting on the shelf, normal NiMh batteries will lose some of their power, typically about 1% a day. You can count on them needing recharging about every 2 to 3 months. In fact, you should plan on doing this to NiMh batteries that sit around all summer, when you don't ride as much at night.

There is a new type of NiMh battery that has been on the market for only a couple of years. They are usually called Low Self Discharge, or Ultra Low Self Discharge (the manufacturers seem to shy away from the LSD acronym for some odd reason). They hold about 85% of their charge after a year. These batteries will typically have a lower current rating, 1.8 to 2 amps as opposed to the 2.5 to 2.7 amp ratings on non LSD NiMh AA cells. Sanyo makes AA cells under the Eneloop brand name that are pretty highly rated. Rayovac makes some under the Hybrid name that I have been very happy with. Tenergy also makes some that I have limited experience with, but the results look promising. You can often find these LSD batteries on sale for less than the non-LSD type. I haven't seen LSD cells available in pre-assembled NiMh battery packs. The most commonly available size is AA, though C and D cells are becoming available.

The user interface:

At first glance, it seems sort of obvious. There is a button on the back. You would expect to push it and have the light turn on. Indeed that's what it does. But if you don't understand how it is programmed, what happens the next time you push the button may seem confusing.

You can think of the light as having three modes: headlight, flasher, and off. Each of the modes can have sub-modes. You switch between sub-modes and modes by using different length button presses.

Button Presses:

The light responds to three kinds of button presses: tap, push, and hold.

A tap is a press of the button from .05 to 1 second. The lower number is done to handle the imperfect way switches work. Their contacts bounce around when they are first pressed. Waiting for the button to be stable for .05 seconds allows the lights microcontroller to be sure the user pressed the button. But I digress.

A push is a press of the button that lasts for 1.5 to 3 seconds.

A hold of the button is a press that lasts for more than 4 seconds and less than 10.

Headlight mode:

Let's look at the headlight mode. It normally switches to the next sub-mode with a tap of the button. The default programming for the headlight mode allows the user to cycle between sub-modes in the following order: high, medium, high, low, high, medium, etc. High is the maximum brightness the LED can produce, medium is around 66%, and low is about 33%.

The idea behind the above pattern is to make sure that maximum light output is never more than a quick tap away. You may use the light in low when climbing a hill, come over the crest, and with one tap, you have switched the sub-mode to high, so you will be ready to blast downhill without having to switch thru sub-modes you don't need.

One reason to use a lower level than high when climbing, or riding slowly, is it will conserve battery power. If you run your light in medium all the time, your battery will last nearly twice as long as it would if you had the light on high.

You can set the brightness levels for low and medium. I'll cover that in the programming appendix. You can also change the number of sub-modes to be just 2, so you don't have to cycle thru as many.

Flasher mode:

The flasher has 4 sub-modes: emergency beacon, flash, blink, and hi-lo.

Emergency beacon is 3 quick bursts of light, followed by about 2/3 of a second of no light. It looks very much like the flash pattern you sometimes see on tow trucks or emergency services vehicles. I've had people stop me and say they thought I was some kind of police vehicle when I've been running the flasher in this sub-mode. Which is just fine with me. The flasher gets oncoming traffic's attention, often they slow down. Which is great if some jerk behind you decides to pass on a blind turn or when going over a hill. The good people who slowed down might have enough time to get out of the jerk's way. Emergency beacon runs the LED for about 25% of the time.

Flash is a simple on off on off etc. kind of flash. It flashes about 3 times a second. It gets folks attention, but is a bit less intimidating than the emergency beacon. Flash runs the LED about 50% of the time.

Blink runs the LED on for most of the time. About once a second, it will switch to a dim setting for less than 1/10th of a second. The overall effect is kind of subtle. I like this sub-mode for riding near dawn or dusk, when it's nice to have a bit of light to see by. The 1/10th of a second blink gets oncoming drivers attention. This sub-mode is probably equivalent to running the LED about 95% of the time.

Hi-Lo runs the LED thru a high-low pattern about twice a second. It looks very much like motorcycle lights that have this kind of feature. It's good for daylight running. It's pretty noticeable to oncoming traffic, but doesn't look like any kind of warning flasher. Hi-Lo

All of the flasher sub-modes use the last headlight sub-mode to set the maximum output of the LED. For example, if the last headlight sub-mode was medium, the Hi part of a Hi-Lo flash would be about as bright as the headlight is when it's run at medium. The Lo part will be pretty dim.

Why is the flasher mode implemented this way? It allows you to make the flasher sub-modes brighter or dimmer as needed. By running the flasher at a lower brightness, you will greatly extend your battery run time.

Off mode:

Off mode basically turns the LED off. It also remembers the last way you had the light set up when you turned it off.

You enter off mode by holding the button down for about 4 seconds. If you are in the headlight mode, you will briefly go into flasher mode and then shut off about a second later.

You exit off mode by pressing the button for at least 1/4 of a second. I may make the length of this press longer in the future. Some people have reported that lights have turned on when stored in their packs. The 1/4 button press requirement will hopefully eliminate some of that. The best way to avoid having your light turn on unexpectedly in a backpack, is to remove the batteries before storing it there.

While the BFL-1000 is in off mode it's microcontroller is still running, but in a very low power mode. If you left your light plugged into a fully charger 9.6 volt NiMh battery like the one we discussed earlier, the light would take over 6 months to drain the battery. If you will be leaving the light off for an extended period of time, it's best to disconnect the battery from the light.

Warning System:

The BFL-1000 has a few features to let the user know if things aren't quite right.

When you plug the BFL-1000 into a battery, it will blink on and off very rapidly 3 times. If you notice this blink happening while you are riding, you should look for a loose connection between the battery and the headlight. If you plug the headlight in and it doesn't blink, it is possible the microcontroller failed to reset. This doesn't happen very often. Try unplugging the headlight, wait 10 seconds, then plug it back in. If trying this a few times fails to work, you may have a dead battery, or a malfunctioning BFL-1000.

The BFL-1000 regulates the temperature of the LED to avoid frying it. LEDs are way more efficient at producing visible light than an incandescent bulb, but they don't radiate IR heat the way an incandescent does. Usually this is not a big issue when riding. A speed of 3 or 4 miles per hour usually provides enough air flow to keep the BFL-1000's housing cool. If you stop to check a map or chat at an intersection, the LED may start to warm up. Eventually the microcontroller will detect that the LED is too hot. It will flash the LED twice, and then turn down the brightness. It will continue doing this every 30 seconds till the LED is cool enough. Typically you will only see a couple of the flashes before the LED has cooled down.

The BFL-1000 measures battery voltage. It will flash the LED three times when the battery voltage gets below a warning level. For the 9.6 volt battery we discussed, it will start doing the warning flashes when the battery voltage gets down to around 8.5 volts. It will do the triple warning flash about every 30 seconds. If you switch the LED to a lower brightness level, this will often stop the warning flashes for a few minutes, as the battery voltage will climb up from the warning level due to the reduced load. But you will need to replace your battery soon. In the section on programming the BFL-1000 we will discuss how to set the warning level for the type of battery you want to use with the light.

Appendix A: BFL-1000 User Programming Options

The user interface behavior can be changed pretty easily for different types of riding. A road rider may want access to the flasher modes, a mountain bike racer may only want 2 light levels, low for riding thru dust kicked up by other riders and high. Users may find the factory programmed low and medium light levels to be too dim or too bright for the conditions they are riding in. The user will also need to change the low battery warning level if switching to different voltage batteries.

To access the BFL-1000 programming features, press the button and hold it like you would to turn the light off, but keep holding the button down.

After 10 seconds, you will enter the first of the programming options. Each option consists of a number of blinks repeated 3 times. If you release the button during the time these blinks are being repeated, you will have selected or changed that option. There is a 2 second pause between option blinks, during that time you can release the button and change nothing. So if you wanted to disable the flasher, you would press and hold the button for 10 seconds, you would see 3 sets of 3 blinks, the light would go out for 3 seconds, and you would then see 3 sets of 5 blinks. If you release the button during any time during those 3 sets of 5 blinks, you will disable the flasher.

Blinks----Option:
3----------2 or 3 light levels
5----------enable or disable flasher modes
7----------set low brightness level
9----------set high brightness level
11-------- set battery warning level

2 or 3 light levels
This option is a toggle. If your light cycles thru 3 light levels and you release the button while it is cycling thru the 3 blinks for this option, your light will now only do 2 light levels. With 3 light levels you cycle thru high, low, high, medium. With 2 light levels you cycle thru high, low, high, low.

Enable or disable flasher
This option is a toggle. If your light can be put into flasher mode with a button push and you would like to get rid of the flasher functionality, just enter programmming mode and release the button when the light is cycling thru it's 3 sets of 5 blinks. After you have disabled the flasher, a button push will now turn the light off (you will only need to press and hold the button for 2 seconds to turn off the light instead of the 4 seconds it would take with the flasher enabled). Conversely, if you would like to re-enable the flasher after having disabled it, just repeat the above procedure.

Set low brightness level
This option is allows you to select the light level used for the low headlight setting. As before, enter programming mode and wait for 3 sets of 7 blinks, then release the button. The light will begin to ramp up in brightness, taking about 2 seconds to go from a very dim setting to full brightness. It will repeat this ramp 5 times. Just press the button to select the level the light is at any time during the ramping.

Set medium brightness level
This works exactly like setting the low level, except you need to wait for 9 blinks. Please note that you can set your medium brightness level to be dimmer than your low brightness level if you want to.

Set the low battery warning level
Enter programming as mentioned above, and wait for 11 blinks. If you start with a fresh set of batteries, the light will automatically figure out what warning level to use. About 2 seconds after you release the button, the light will blink to indicate what the battery warning voltage level is set to:
2 blinks = 6.5 volts, good for 7.4 volt LiIon battery or 7.2 volt NiMh battery
3 blinks = 8.5 volts, good for 9.6 volt NiMh battery
4 blinks = 9.9 volts, good for 11.1 volt LiIon battery or 12 volt NiMh battery
5 blinks = 12.5 volts, good for 14.8 volt LiIon battery or 14.4 volt NiMh battery
6 blinks = 16.5 volts, good for 18.5 volt LiIon battery or 19.2 volt NiMh battery
7 blinks = 20.0 volts, good for 22.2 volt LiIon battery or 24 volt NiMh battery

The above warning levels should cover most of the battery packs you'll find commercially available.

That's All Ffffolks!

Whew, this came out longer than I expected!!!

Anyway, I've pretty much decided the BFL-1000 will not be a product. I have a new driver chip I'm using. I guess I'll call the new light the BFL-1001 or something. It will operate on a lower voltage, like down to around 6 volts. So it could be used with a 7.2 volt NiMh battery or a 7.4 volt LiIon.

I also will have a 2 led version (20 watts, some of you saw it at the Walkway Over The Hudson circus), maybe I'll call it the BFL-2001. It puts out over 1200 lumens.

I've made a couple of prototype rear lights as well. The one some of you have seen me riding with is a 6 watt setup that uses two 3 watt red-orange LEDs and puts out around 350 lumens. I'm thinking I'll name it the BRL-2001. It's pretty bright. There are newer LEDs coming down the pike that will probably let me do a 1000 lumen rear light before the end of 2010.

Pete and Erik,

Let me know if any of the above makes any sense. And please let me know if you find any problems with the lights. I'm thinking of changing battery connectors (again). The ones you have are called tamiya, and are pretty standard for RC car batteries.

Matt B,

Let's go do some nite riding sometime, so I can give you an upgraded light.

Everyone else,

If anyone else has comments on the above manual/design spec, please jump on this thread. Are there any features you've always wanted in a bike light ? I know Pete wants the ability to have the light flash morse code he programmed into it, and I was actually considering a feature like that but ran out of room in the microcontroller.

I've got a few BFL-1000 prototypes almost finished. If anybody else would like to be a test subject ... err I mean beta tester, let me know. I'll probably sell completed lights and an 8 AA cell holder, plus some velcro straps and other junk for around $100. If you want batteries and a pretty decent charger, I'll toss one of those in for $30. If you want a light that has lots of fancy mounts for the battery and light, you should probably look at something else. If you want a light that will run off a bunch of different types of batteries, and like to dink around with wiring stuff up, these could be a good deal for you.



Above is view of the Cree MCE 10 watt LED, Fraen reflector, and sexy anodized aluminum tubing.



A bottom view showing the button and power cables at the back end. The hole on the bottom is a threaded rivet used to attach the light to the mount.

I took some pictures of the battery cover (condom, whatever). The cover is a 29er tube with one end glued shut. You stick the battery pack in and fold the other end over. With a couple of velcro straps it hung onto my stem quite well for 5 hours of bike patrolling today. Seemed to be fairly waterproof:







Preview of the BFL2001:



It's basically 2 of the LEDs used in the BFL1000 in a 2 inch by 2.5 inch case, about .9 inches thick. I took it out Thursday night at Jockey Hill with Pokey. Pokey's comment was "We cut quite a swath through the night".

I'll bring some lights for folks to look at to this month's meeting. I'll wait till after official business is over. I don't want to over-commercialize the monthly meetings.

OBL

PS went out after dark and did some beamshots on a local trail. I don't think the BFL1000 shots really do it justice. Plus I had the camera on a 6 second exposure time, so I may have wiggled the bike a bit during that time.

First BFL1000 on medium:


Then the BFL1000 on high:


Finally, the BFL2001 on high:


The small ramp you can clearly see the trail going up in the BFL2001 shot is about 150 feet from the headlight. I tried to keep the bike in same position for all shots and the camera was sitting on an old bridge abutment behind me. Aiming the lights and the camera, without being able to look at the camera's viewfinder made the whole operation not as repeatable as I'd like. But hopefully it gives you some idea of how bright these lites are. Or come to Wednesdays meeting and try one yourself.
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Last edited by oh_blinding_light on Mon Oct 12, 2009 8:23 pm; edited 4 times in total
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slave2bacon



Joined: 17 Oct 2006
Posts: 789
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PostPosted: Wed Oct 07, 2009 8:18 am    Post subject: Reply with quote

I took the OBL hand made light kit out to Jockey Hill for a test run this week. It worked great and has light that rivals my Night Rider HID. It's a simple and effective unit. Mark - maybe do a demo at the next meeting?
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SketchyRydr



Joined: 01 Jan 2007
Posts: 57
Location: Kingston

PostPosted: Wed Oct 07, 2009 6:29 pm    Post subject: light Reply with quote

I used the light on an evening road ride and it got lots of attention. My friend who met me on the reservoir walkway said he could see the light coming a mile away!
Now I need a complimentary tail light to complete the package.
The modes are a bit confusing to work out, but I'm sure after a couple of rides it will be intuitive.
Thanks for letting me try such a great quality product!
-E
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Bikegeek



Joined: 06 Oct 2006
Posts: 328
Location: Dropping in...

PostPosted: Wed Oct 07, 2009 7:08 pm    Post subject: Reply with quote

Pics Question
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oh_blinding_light



Joined: 15 Oct 2008
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Location: People's Republic of Rosendale

PostPosted: Wed Oct 07, 2009 7:52 pm    Post subject: Reply with quote

Pete & Erik,

Thank you for the kind reviews.

Erik, I already have a taillight in the works. You no doubt noticed the blinding red-orange one I had at the walkway across the Hudson opening. Or maybe not, with your pursuit bike you were way out in front of me most of the time Very Happy .

The taillight uses two luxeon III LEDs and puts out around 350 lumens, but with a very wide beam, probably close to a 120 degree spread. It is comparable to a Dinotte 400R taillight, but maybe a tad brighter. I hope to sell the taillight assembly (sans batteries) for around $100. I know that seems like a lot for a taillight, but compare it to the cost of the Dinotte taillights.

When road riding with it, I typically have motorists slow down and pass me in the other lane because they aren't sure what I am (Emergency vehicle, police car, UFO?).

Bikegeek, I'll edit the original manual post to include some pictures, probably tomorrow.

OBL
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Bikegeek



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PostPosted: Wed Oct 07, 2009 8:44 pm    Post subject: Reply with quote

Gracias Wink
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Tim845



Joined: 02 Sep 2006
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PostPosted: Thu Oct 08, 2009 12:03 am    Post subject: Reply with quote

Simpler user interfaces are great, but a fuel gauge is a great feature.

Night riding is a great way to see the same places differently...tonight:
This spider is pretty common on warm fall nights in Hyde Park- the lights catch their eyes:

Lights saved my ass from someone else's:

Endo'd, and moon:

These stand out:



Nothing says "Back Off" like a 1000 lumens tail light!
Ive only got 800 for my headlights!

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Alan W



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PostPosted: Mon Oct 12, 2009 11:53 am    Post subject: Reply with quote

How can one go about buying those lights? Looks like a great deal ...
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oh_blinding_light



Joined: 15 Oct 2008
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PostPosted: Mon Oct 12, 2009 4:24 pm    Post subject: Reply with quote

I have a handful of prototypes I'll bring to this month's meeting (this Wednesday, no?). I'll drag along some batteries and chargers as well, though I have more lights at the moment.

You can check them out there and buy one if you like the way it looks. I'll include a one year warranty on the lights and one or two firmware upgrades (if they become necessary).

After the meeting (if I don't sell out Smile , well I can dream can't I?), I'll post something in the "Buy, Sell, Trade" forum.

Eventually I hope to have a web site to sell the next generation off of. I'll include links for battery suppliers and have a few technical sections on how to wire up your own battery packs, etc. Once the web site is working, I'll ad a link to it from this posting and whatever I put in the "Buy, Sell, Trade" forum.

OBL

PS Oh Mighty Tim (Pedaler845),

I agree a fuel gauge would be a pretty nice feature, but not really feasible in this version, I have almost no memory left and 1 unused pin. I figure blinking the light when it's time to change the battery is better than no warning at all.

There are places that sell fuel gauges for LiIon packs. You could always get one of these, cover it in clear heatshrink, and glue it to the side of your existing battery.

For example, here's some:

3.7V pack = http://www.batteryspace.com/fuelgaugeforpcbof37vli-ionbatterypack.aspx

7.4V pack = http://www.batteryspace.com/fuelgaugeforpcbof74vli-ionbatterypack.aspx

11.1V pack = http://www.batteryspace.com/fuelgaugeforpcbof111vli-ionbatterypack1.aspx

14.8V pack = http://www.batteryspace.com/fuelgaugeforpcbof148vli-ionbatterypack.aspx

I've never played with one these, but it looks like it'd be pretty easy to cut the plug off and wire it up to a battery pack. Maybe a better idea would be to build a thru plug with the gauge in the middle. Battery plugs in one side and the light plugs in the other. That way you could use it with any of your battery packs of the same voltage. The type I posted links for will only work on a Lithium chemistry battery, NiMh and NiCad batteries would require a more expensive gauge.

With the price these guys sell fuel gauges for, I'd much rather have an article on my web page the describes how my friend the Mighty Tim got one of these to work, than try to sell them myself. If you decide to buy one, let me know, I'll order one or two for me and we can split the shipping (that's what always kills you on these kind of cheap products).
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oh_blinding_light



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PostPosted: Wed Oct 14, 2009 7:36 pm    Post subject: Reply with quote

I think Mr Cobain said it best:

Quote:

All apologies.
What else could I say?


After a lengthy afternoon of packaging up a few lights (finding the various parts in my garage took a while), I discover we are having a nasty frost this evening. So I spend some time draining garden hoses, shutting off outside faucets, all those responsible home owner type things. I run a bit late doing these domestic chores and decide to drive to the FITC monthly meeting (I was originally planning to ride).

My truck's battery is dead.

So: apologies to those who hoped to see my new and newest lights at the meeting.

I'll bring them to the Minnewaska Master Plan hearing (and the pre-ride if there is one ... more on that after I make some more calls). And I might as well check out the Halloween Ride.

OBL

PS Pete and Erik look for a PM from me soon.
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oh_blinding_light



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PostPosted: Thu Dec 31, 2009 7:01 pm    Post subject: Reply with quote

I've heard a few non FITC members have read about my lights and been frustrated at not being to reach me. Well you could always join the club and PM me or I can be reached via email: [email protected]

I made some changes to the user interface and have decided to dump the BFL-1000 in favor of the dual LED BFL-2001 (see my review of the MJ-808). I decided it was time to update this post.

This isn't finished yet. It needs a bit more editing.

Most of the user interface changes mentioned will be available to folks who bought a BFL-1000 at no charge, you just need to get the light to me for an hour or so.

The user interface description also applies to the BRL-2001, my 380 lumen tail-light. It typically isn't very useful when trail-riding, but you could use it as an emergency light to get yourself out of the woods if you break your headlight. Or if I could get Pokey to use one, I might be able to find him in the woods at night, especially after a long uphill grind.

OBL

Some UPDATED thoughts on a High Powered LED Bike Light and it's user interface

The BFL-2001 is high intensity LED driven by a current controlled buck converter. The buck converter is controlled by a small 8 pin microcontroller. Software programmed into the microcontroller determines the user interface for the light and handles tasks such as warning the user when the light becomes too hot, or the battery is getting low.

The LEDs used in the light are a pair of CREE MCEs. The light uses about 20 watts of power and produces between 1200 and 1300 lumens of light. This is roughly 2.5 to 3 times times the efficiency of a halogen bulb. Because LEDs can be switched on and off very quickly (a process known as pulse width modulation, or PWM), they can be made to appear dimmer by varying the percentage of time the light is really on for. This happens at such a high frequency (several thousand times a second), that you will never notice it. The advantage to dimming a light this way, is you draw less power and can extend your battery life. If you run a LED light at half brightness, you get roughly twice the run time from your battery. Note: it is not possible to dim most HID lights, but you can do pwm dimming with a halogen light

Some of you will ask, what's a lumen? It's a measure of the total amount of light produced by a light source. It is kind of subjective, because it takes into account how bright a light source looks to a person, and the human eye is more sensitive to some colors than others. A couple of examples: a household 60 watt light bulb produces about 800 lumens, a 20 watt mr-11 halogen light bulb produces around 400 lumens.

Power sources:

The BFL-2001 is designed to operate from any voltage source producing between 8 and 24 volts that is capable of producing enough current (more on that later). Below 8 volts, the light will still operate, but will begin to dim. The buck converter allows the light to produce about the same brightness from any voltage source that meets the above requirements. For practical purposes the lowest voltage battery I'd recommend is a 9.6 volt NiMh battery.

Batteries, beside being rated to provide a particular voltage are rated to provide a certain amount of current, often stated in mAh (an abbreviation for milli ampere hours, 1000 mAh are equal to 1 Ah). A battery rated at 2200 mAh can deliver a current if 1100 mA (milli amperes) for about 2 hours.

A quick approximation for figuring the run time of a battery with a particular light is to multiply the battery voltage by the current it can produce to obtain the watts the battery can deliver (a 1 volt battery delivering 1 amp of current for 1 hour, has produced 1 watt-hour of power). This is the number of watts your battery can provide under ideal conditions. Divide the number of watts the battery can deliver by the number of watts your light uses and you arrive at the number of hours your light should run. I usually fudge the run time a battery can provide by multiplying the calculated time by 80% to allow for batteries not being rated correctly by the manufacturer, batteries not being fully charged, etc.

The BFL-2001 can also run from a variety of Li-Ion (lithium ion) batteries. Some people prefer Li-Ion batteries because they weigh a bit less than NiMh, and should, in theory, hold a charge for longer. They do cost more, typically 2 to 3 times as much as NiMh batteries. They need a special charger. Never, never attempt to use a NiMh charger with a Li-Ion battery. Li-Ion can be a safety hazard. They have been know to spontaneously burst into flames (typically while being over-charged or physically abused).

The 2 most common types of Li-Ion batteries available to consumers are Li-Ion 18650 cells, and Lithium Polymer (LiPo) batteries. 18650 cells typically provide 3.7 volts at around 2200 mAh, and are wired in series and parallel to provide the voltage and current you desire. Lithium Polymer batteries come in a variety of sizes, voltages, and current capacities. 18650 cells are often used in laptop computer batteries. LiPo batteries are often used in remote control (RC) aircraft and cars

Which battery type is better?

You will find some Li-Ion batteries available for quite cheap prices from a few Chinese importers. In my experience, you should treat these cheap batteries with caution. I've had a couple just suddenly stop working. I don't know if this is typical, but they failed in an open state. One cell in a pack of 4 wired in series suddenly died and the whole pack stopped working. This would have sucked if I had been hurtling downhill at the time.

More expensive Li-Ion batteries will have some kind of protection built in. This protection circuit will prevent the battery from being over charged or over discharged. It also will typically act as a fuse to prevent problems if a battery is accidentally shorted. You should always use batteries that have a protection circuit built in. One possible downside to this, is the protection circuit could shut off the battery while you are using it. This is one of the reasons the BFL-2001 has a low battery warning feature.

Lithium Polymer (LiPo) batteries typically come with no protection circuit board. LiPo batteries are mostly used in radio controlled aircraft, where you want a light high powered battery, that won't suddenly stop working. Since these usually have NO safety circuit built in, use them with extreme care. You should never overcharge a LiPo or discharge it below about 3 volts per cell.

NiMh batteries have their problems as well. They don't do well if discharged too deeply. A good rule of thumb is never run a 1.2 volt NiMh cell below about .8 volts. For an 8 cell pack, never run the pack below 6.4 volts. A more conservative rule, would be never run the pack below 8 volts.

NiMh batteries don't like to be overcharged. Don't cheap out on the type of charger you use with your NiMh batteries. A "smart" charger will charge the batteries till it sees a slight bump in the battery voltage. Most cheap chargers will just start a timer when a battery is plugged into them. This can overcharge the battery if it was not fully drained beforehand. One sign of a cheap charger is if a nearly fully charged battery is plugged into it, it will heat up the pack (it will become very warm to the touch, a bit of warmth is OK), and not shut off. A smart charger, will try to charge a fully charged battery for a few minutes (an hour at most), and then shut off.

NiMh batteries exhibit a problem known as self-discharge. Just left sitting on the shelf, normal NiMh batteries will lose some of their power, typically about 1% a day. You can count on them needing recharging about every 2 to 3 months. In fact, you should plan on doing this to NiMh batteries that sit around all summer, when you don't ride as much at night. NiMh batteries are often available from stores that specialize in RC cars. On a dollar per watt basis they are usually the least expensive type of battery.

There is a new type of NiMh battery that has been on the market for only a couple of years. They are usually called Low Self Discharge, or Ultra Low Self Discharge (the manufacturers seem to shy away from the LSD acronym for some odd reason). They hold about 85% of their charge after a year. These batteries will typically have a lower current rating, 1.8 to 2 amps as opposed to the 2.5 to 2.7 amp ratings on non LSD NiMh AA cells. Sanyo makes AA cells under the Eneloop brand name that are pretty highly rated. Rayovac makes some under the Hybrid name that I have been very happy with. Tenergy also makes some that I have limited experience with, but the results look promising. You can often find these LSD batteries on sale for less than the non-LSD type. I haven't seen LSD cells available in pre-assembled NiMh battery packs. The most commonly available size is AA, though C and D cells are becoming available. The AA Low Self Discharge batteries make an excellent backup battery for the BFL-2001. Eight of them in an inexpensive 8 cell battery holder will give you nearly an hour of run-time on the brightest level.

The user interface:

At first glance, it seems sort of obvious. There is a button on the back. You would expect to push it and have the light turn on. Indeed that's what it does. But if you don't understand how it is programmed, what happens the next time you push the button may seem confusing.

You can think of the light as having three modes: light, flasher, and off. Each of the modes have sub-modes. You switch between modes and sub-modes by using different length button presses.

Button Presses:

The light responds to three kinds of button presses: tap, push, and hold.

A tap is a press of the button from .05 to 1 second. The lower number is done to handle the imperfect way switches work. Their contacts bounce around when they are first pressed. Waiting for the button to be stable for .05 seconds allows the lights' microcontroller to be sure the user pressed the button.

A push is a press of the button that lasts for 1.5 to 3 seconds.

A hold of the button is a press that lasts for more than 3 seconds and less than 8.

Light mode:

When the BFL-2001 is in the light mode the LEDs appear to be on steadily at 2 or 3 different brightness levels (the number of levels is a user programmable option). It normally switches to the next level (or sub-mode) with a tap of the button. The default programming for the light mode allows the user to cycle between levels in the following order: high, medium, low, high, medium, low, etc. High is the maximum brightness the LED can produce, medium is around 66%, and low is about 33%.

One reason to use a lower level than high when climbing, or riding slowly, is it will conserve battery power. If you run your light at the medium level all the time, your battery will last 50% longer than if you had the light on high. If you run your light at the low level all the time, your battery will last 3 times as long.

You can set the brightness levels for low and medium. I'll cover that in the programming appendix. You can also change the number of levels to be just 2, so you don't have to cycle thru as many. This might be handy if using the light when racing. A racer might be interested in having a low level that allowed him to see the trail when racers in front of him had churned up a lot of dust, but he would run the light on high the rest of the race to allow him to ride at the fastest speed.

Flasher mode:

The flasher has 4 patterns (or sub-modes): beacon, flash, blink, and hi-lo.

Beacon is 3 quick bursts of light, followed by about 2/3 of a second of no light. It looks very much like the flash pattern you see on tow trucks or emergency services vehicles. I've had people stop me and say they thought I was some kind of police vehicle when I've been running this flasher pattern. Which is just fine with me. When the flasher gets traffic's attention, they often slow down. Beacon runs the LEDs for about 25% of the time.

Flash is a simple on, off, on, off, etc. kind of flash. It flashes about twice a second. It gets folks attention, but is a bit less intimidating than the emergency beacon. Flash runs the LEDs about 50% of the time.

Blink runs the LEDs on for most of the time. About once a second, it will switch to a dim level for less than 1/10th of a second. The overall effect is kind of subtle. I like to use this mode on my headlight when riding near dawn or dusk, when it's nice to have a bit of light to see by. The 1/10th of a second blink gets oncoming drivers attention. This mode is probably equivalent to running the LED about 95% of the time.

Hi-Lo runs the LED thru a high-low pattern about twice a second. It looks very much like motorcycle lights that use a headlight modulator. It's good for daylight running. It's pretty noticeable to oncoming traffic when run on your headlight. On a tail-light it is very noticeable in bright sunlight.

All of the flasher patterns use the last light mode level to set the maximum output of the LED. For example, if the last light level was medium, the Hi part of a Hi-Lo flash would be about as bright as the headlight is when it's run at medium. The Lo part will be pretty dim.

Why is the flasher mode implemented this way? It allows you to make the flasher brighter or dimmer as needed. By running the flasher at a lower brightness, you will greatly extend your battery run time. The ability to adjust the flasher brightness levels is very handy in the BRL-2001 tail-light when riding in a group. Turn the level down to avoid blinding riders right behind you.

Off mode:

Off mode basically turns the LED off. It also remembers the last way you had the light set up when you turned it off.

You enter off mode by holding the button down for about 2 seconds. The LEDs will turn off. Release the button. I decided to use a long press to turn the light off to prevent a rider from accidentally turning off the light.

If press the button while in the Light mode, the light will turn off after 2 seconds. If you continue holding the button, you will switch to the Flasher mode. Similarly if you are in the Flasher mode and hold the button down for 2 seconds, the light will turn off, and if you continue holding the button your will enter the Light mode.

You exit off mode by pressing the button for at least 1/4 of a second. The LEDs will come on at about half power. When you release the button the light will return to the last mode it was in before you turned it off. So for example if you were in the flasher mode and turned the light off, when you turn it on again, it will be in the flasher mode.

Some people have reported that earlier versions of the lights turned on when stored in their packs. The 1/4 second button press requirement will hopefully eliminate some of that. The best way to avoid having your light turn on unexpectedly in a backpack, is to unplug your battery before storing it there.

While the BFL-2001 is in off mode, it will continue to draw a very small amount power in the off state, typically something like 1/2 of a mA per hour. You could leave it plugged into a 2200 mAh battery pack for 2 weeks and drain less than 1/10th of the batteries capacity. If you are not using the light for a few hours, it's a good idea to unplug the batteries.


Warning System:

The BFL-2001 has a few features to let the user know if things aren't going well. It will warn you of intermittent connections, low battery voltage and high LED temperatures.

When you plug the BFL-2001 into a battery, it will blink on and off very rapidly 3 times. If you notice this blink happening while you are riding, you should look for a loose connection between the battery and the headlight. If you plug the headlight in and it doesn't blink, it is possible the microcontroller failed to reset. This doesn't happen very often (I have only had it happen to me a couple of times and that was due to a misprogrammed microcontroller. Try unplugging the headlight, wait 10 seconds, then plug it back in. If trying this a few times fails to work, you may have a dead battery, a break in your power cable or a malfunctioning BFL-2001.

The BFL-2001 regulates the temperature of the LEDs to avoid frying them. LEDs are way more efficient at producing visible light than an incandescent bulb, but they don't radiate IR heat the way an incandescent does. Usually this is not a big issue when riding. A speed of 3 or 4 miles per hour usually provides enough air flow to keep the BFL-2001's housing cool. If you stop to check a map or chat at an intersection, the LEDs may start to warm up. Eventually the microcontroller will detect that the LEDs are too hot. It will flash the LEDs three times, and then turn down the brightness. It will continue doing this every 30 seconds till the LED is cool enough. Typically you will only see a few of the flashes before the LED has cooled down.

The BFL-2001 measures battery voltage. It will flash the LED three times when the battery voltage gets below a warning level. For a 9.6 volt NiMh battery, it will start doing the warning flashes when the battery voltage gets down to around 8.5 volts. It will flash the LEDs 5 times about every 30 seconds. If you switch the LED to a lower brightness level, this will sometimes stop the warning flashes for a while, as the battery voltage will climb up from the warning level due to the reduced load. But you will still need to think about replacing your battery soon. In the section on programming the BFL-2001 we will discuss how to set the warning level for the type of battery you want to use with the light.

You can temporarily halt warning flashes (for overheating or low voltage) simply by changing light level or flasher mode. Doing so will stop the warning flashes for about 10 minutes. Note: turning off the warning flashes will not stop the microcontroller from turning down the LEDs light level if the LEDs are overheating.

Appendix A: BFL-2001 User Programming Options

The user interface behavior can be changed pretty easily for different types of riding. A road rider may want 3 light levels. A mountain bike racer may only want 2 , low for riding thru dust kicked up by other riders and high. Users may find the factory programmed low and medium light levels to be too dim or too bright for the conditions they are riding in. The user will also need to change the low battery warning level if switching to different voltage batteries.

To access the BFL-1000 programming features, press the button and hold it like you would to turn the light off, but keep holding the button down. If you were in the light state, the light will turn off, it will enter the flasher state for about 5 seconds and will then turn off for another 5 seconds. Keep holding the button down. Eventually the light will begin to to do a series of bright / dim flash patterns. Each pattern is repeated twice. There is a 1 second pause between flashes that make up the pair of flashes where the LEDs are off. Once this pair of flashes has started and during the 1 second break in between, if you release the button, you have selected to change a programmable option.

Between flash pairs, there will be a 3 second pause where the LEDs are off. You may release the button during that time to exit programming mode return to normal light operation.

Blinks----Option:
3----------2 or 3 light levels
5----------set low brightness level
7----------set high brightness level
9--------- set battery warning level

2 or 3 light levels
This option is a toggle. If your light cycles thru 3 light levels and you release the button while it is cycling thru the 3 blinks for this option, your light will now only do 2 light levels. With 3 light levels you cycle thru high, low, medium, high, low, medium, etc. With 2 light levels you cycle thru high, low, high, low.

Set low brightness level
This option is allows you to select the light level used for the low headlight setting. As before, enter programming mode and wait for 2 sets of 5 flashes, releasing the button sometime during the flashes. The light will begin to ramp up in brightness, taking about 5 seconds to go from a very dim setting to full brightness. It will repeat this ramp 5 times. Just press the button to select the level the light is at any time during the ramp in brightness

Set medium brightness level
This works exactly like setting the low level, except you need to wait for 7 flashes. Please note that you can set your medium brightness level to be dimmer than your low brightness level if you want to. That would make your 3 level light switch like: high, medium, low, high, etc.

Set the low battery warning level
Enter programming as mentioned above, and wait for 9 flashes. If you start with a fresh set of batteries, the light will automatically figure out what warning level to use. About 2 seconds after you release the button, the light will flash a 3 digit value to indicate what the battery warning voltage level is set to. The value is flashed with 1 flash representing 0, and 10 flashes representing 9. For example, the pattern 1 7 6 would translate to 065 and would represent a low warning voltage of 6.5 volts.

Warning flashes:
1 7 6 ... 6.5 volts, good for 7.4 volt LiIon battery or 7.2 volt NiMh battery
1 9 6 ... 8.5 volts, good for 9.6 volt NiMh battery
1 10 10 ... 9.9 volts, good for 11.1 volt LiIon battery or 12 volt NiMh battery
2 3 6 ... 12.5 volts, good for 14.8 volt LiIon battery or 14.4 volt NiMh battery
2 7 6 ... 16.5 volts, good for 18.5 volt LiIon battery or 19.2 volt NiMh battery
3 1 1 ... 20.0 volts, good for 22.2 volt LiIon battery or 24 volt NiMh battery

The above warning levels should cover most of the battery packs you'll find commercially available.

That's All Ffffolks!

I'm using the above interface in my new tail-light, which I think I'll call the BRL-2001. It uses 2 Luxeon III red-orange LEDs and produces about 380 lumnes. It uses 6 watts if run in the light state on high. It's pretty bright. There are newer LEDs coming down the pike that will probably let me do a 750 lumen rear light before the end of 2010.

If anyone else has comments on the above manual/design spec, please jump on this thread. Are there any features you've always wanted in a bike light ?

The BFL2001:



It's basically 2 of the LEDs used in the BFL1000 in a 2 inch by 2.5 inch case, about .9 inches thick. I took it out last November at Jockey Hill with Pokey. Pokey's comment was "We cut quite a swath through the night".

I went out after dark and did a beamshot on a local trail.

The BFL2001 on high:


The small ramp you can clearly see the trail going up in the BFL2001 shot is about 150 feet from the headlight.

OBL
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