Brunton L5 Headlamp for Dental Use?

Recently the headlamp salesmen have been swarming around school as thick as flies on stink, trying to sell $800 headlamps to all the dental students.  While I recognize the utility of headlamps, the engineer in me has a lot of trouble paying $800 for a glorified flashlight, so I started looking for alternatives.  Those $800 headlamps are NICE, but $800- gimme a break!

What do you get for $800?  A belt mounted Li-ion rechargeable battery pack and a tiny but painfully bright LED lamp housing that clips onto your dental loupes or an optional elastic head band, and a charger.  The battery pack has a microcontroller that monitors battery charge level and beeps when it's time for a recharge.  There are multiple brightness settings and a yellow filter that swings into place to allow using the lamp while manipulating light-cured dental composites.

I did an extensive search of the web and found what looked like the best, non-dental specific headlamp in existence.  The Brunton L5 is da schiznit!.  While it isn't cheap (list price of $270 but widely available for $150), it has many of the attributes of the $800 dental lamps, including light weight, a belt-mounted rechargeable battery pack, and blindingly bright output (multiple settings).  Unfortunately, I think the L5 is not suitable for dental use because of the lens it spreads and diffuses the beam so much that it will be shining in the patient's eyes all the time.  That said, it is a GREAT headlamp for riding a bike at night, camping, etc., so read on.

During my search for information I found dozens of user reviews of the L5 all over the web.  Unfortunately, I could find very little real info about the lamp, not even on the flashlight-geek web sites (yes, there are actually people who get their kicks collecting flashlights and arguing about them on internet forums!).  For some unknown reason, the Brunton web site has the manual for the L1/L3 headlamp but not the L5, so I have put this page together in case anyone else is looking for this information.

Here's the manual and a separate sheet about the battery:

   

Here's a photo of everything that comes in the package.  The red filter would preserve night vision I guess and might be useable for light cured dental composites.  The white diffuser spreads the beam out even wider.  The filters fit tightly over the lamp housing.

 

Here's the battery pack and its nylon case.  The battery is composed of five, larger-than-AA sized NiMH cells.  As you can see the capacity is labeled as 6V, 4.5 AH.  The connector is a polarized, locking molex-type.  The quarter has been included for size comparison.

Here's the battery pack inside its case.  My postal scale says it weighs 12.2 oz.  It feels pretty heavy in your hand but not when it's hanging from your belt.  There is no belt clip but you can slide a belt under a strap on the back of the battery pack.  There is a horizontal strap that would allow putting the battery pack on a backpack strap.  It also comes with a belt that would have to be used when wearing scrubs.  I think it's silly that they included a belt instead of a belt clip.  A belt clip would work on any pants, including scrubs.  Wouldn't a belt clip be cheaper than a belt?  Hmmmm.

Here's the top of the lamp housing.  The lamp housing, cable, and headband assembly weighs 3.5 oz.  It's really light!  The power switch has a rubber button that should keep out moisture.  There is a rubber seal around the lens, and when you tilt the lamp housing it feels like there is a rubber seal on the pivot.  There are three brightness settings selected by successively pushing the power button.  A fourth setting flashes the lamp at about 2 Hz.  Holding the button down for 2 seconds turns off the lamp.  There three brightness settings are quite distinct.

The front of the lamp housing:  Note the frosted look of the lens- fine for most applications, but not so good for dental use because it spreads the light out a little too much.

Here's the lamp housing rotated to its highest position.

Here's the lamp housing rotated to its lowest position.  It's plenty far down for dental work or anything else you want to do.

Here's the back of the lamp housing showing the heatsink.  There are a lot of cheapo flashlights out there that claim to be 5W lights (just check ebay), but without a heatsink, a 5W LED will heat up and its output will plummet.  And no, there is no cooling fan as some doofus reported on one of the flashlight forums.

Here's the final guide clip on the headband that bends the substantial but light-weight cable downward.  Nice touch!  The cable is jacketed with some sort of rubbery feeling plastic that won't twist or let the cable get tangled.  The headband is 1" wide elastic and is adjustable.

Here's the part of the lamp housing that touches your forehead.  Note the soft rubbery squiggles on the headband that keeps it from slipping if you mount the lamp on a helmet.  Those squiggles cover the entire length of the headband.  Another nice detail!

I used my DMM to check the current drain at all three brightness settings after the battery reached full charge and cooled off to room temperature.  Here's a simple formula for calculating power drain from a battery:  Power (P)= Current (I) x Voltage (E).  I measured the battery voltage to be 7.02V, but that's the no-load voltage.  Under load the voltage should drop to very nearly 6V because NiMH cell chemistry dictates 1.2V per cell (x5 cells = 6V).

Low:  39 mA - should give really long battery life, but not very bright.  Power=0.23 W

Medium: 267 mA - pretty bright and moderate drain.  Power=1.6W

High:  600 mA - VERY bright.  Power=3.6W

The power calculated above is the power delivered by the battery.  The regulator circuit in the lamp housing requires some power of its own (typical efficiency is about 85-90%) so the actual power used by the LED will be about 90% of the power levels shown.  So while this headlamp may use a 5W LED, it is only being operated at about 3.5W.  This is typical flashlight/headlamp marketing BS.  They use a 5W LED (or claim to) and call it a 5W lamp even though it is used at substantially lower power.  What are you gonna do? 

Update February 5th, 2009

I wanted to find out if the lens used was the standard K2 type lens I am familiar with from other projects.  I voided my warranty and opened the case to see.
Warning, Luxeon K2 LEDs have a silicone rubber lens with bond wires embedded in the silicone.  If you apply pressure to the silicone lens you can easily bust the bond wires and kill the LED (like I did before I figured out how to get the case open).  I'm going to show you how to get the case open so you can change the lens yourself without damaging the LED.

Luxeonstar.com sells Luxeon K2 LEDs, lens holders, lenses and loads of other high power LEDs and associated electronics for very reasonable prices.  These aren't the floor sweepings you get from the guys dealers who sell even cheaper on ebay, these are 1st quality, full spec parts.  As I said, I killed the LED while trying to get the lamp housing open so I ordered a new K2 LED for about $8 and a couple different lenses for about $4 each.  You can get narrow beam lenses, wide beam lenses, diffuse lenses, and K2s, stars, etc. in different colors.  As long as you buy a 20mm lens designed for K2 LEDs it will fit in the headlamp.

Opening the Housing

This thing is held together like every other plastic housing- snap fit between the front of the housing and the body with maybe a little glue to keep it from opening easily.  Get a thin piece of metal such as a knife blade into the seam and carefully pry at it until it lets go.  The front of the housing will just pull forward and off after you work it for a while.  Click the pictures below to see larger images.

Lamp housing with the front cover removed    Open housing with lens hlder and lens removed    Housing with lens holder and lens separated from front piece    Lens in lens holder    Lens separated from lens holder

Assembly is just the opposite of disassembly (only much easier).  Just be careful not to allow the plastic lens to put a lot of pressure on the silicone lens of the LED.

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