How does the SF L1 / A2 two stage switch work?

Hi,
I have recently bought an A2 and have an L1 on order.
I was wondering if anyone new the details on how the two stage switching works on these lights. I assume that the clever electronics is built into the switch? As the KL1 head is available as an add on for lights without a two stage switch. Does this mean that the two stage switch can be used on other lights?

Many Thanks
Mark

On the L1, there is no clever electronics, just a resistor. The clever part is the two step engagement. Light push engages a resistive path. Push all the way and the resistive path is shorted.

CM

If thats the case then the electronics for the lamp regulation must all be in the L1 head. It must sense the lower voltage and go into the lower power mode. I assume the same occurs when the battery voltage drops?

Is this the same for the A2? Are the tail switch assemblies the same as fitted to the L1?

Mark

I don't think you are right on that CM. If this would be true, there would be no difference in runtime with LOW or HIGH Beam.
AFAIK (I have been told by someone who should know how it works) it does have to do with different anodisations along the path of the 2-stage switch. The anodisations work like 2 different resistors. The electronic (build into the head!) realises from the incoming current, what mode is demanded and then starts that mode...somehow bridging the switch...

Very state-of-the-art if you ask me
Holger

The L1 and A2 TailCaps are interchangeable.

Al

[ QUOTE ]
ho71ko said:
it does have to do with different anodisations along the path of the 2-stage switch. The anodisations work like 2 different resistors.

[/ QUOTE ]
I don't think so. Have a look at http://forum.flashlight-fan.com/gazouimg/L1SW.JPG

I just tried swapping my A2 and L1 switches, and they are indeed interchangeable just like Size15s says. /ubbthreads/images/graemlins/smile.gif
But I don't know exactly how the switches work, so my usefulness in that matter ends right about here. /ubbthreads/images/graemlins/jpshakehead.gif

ho71ko,

With all due respect, I am right. I have dissected an L1 and how I described it is the way it *does* work, unless Surefire made major changes to their design.

Sorry to burst your bubble but it is by no means "state of the art". It is a clever mechanical means I must admit. The way it works is that with the series resistor in the circuit, the boost regulator is running wide open, with the resistor providing the current limiting (actually, it drops the voltage) to keep the boost converter out of regulation. WHen the resistor is bypassed, full current from the cell can now drive the circuit into full regulation. There is a difference in runtime between high and low precisely because of this resistor. When in low beam, the current drawn is very low compared to full regulation.

I don't know where the idea of using different anodizations to realize a resistor came from. It is not a process that can be controlled precisely, not to mention a very expensive one. Why not just use an SMT resistor (just like Surefire did) Also the electronics in the head has absolutely no intelligence whatsover. In principle it works just like any other boost regulators. Only in the L1, the circuit is mostly controlled by HC04 type inverters which can be had for pennies. It doesn't use a monolithic IC controller (like the ones from Linear Tech, Maxim, National etc.) like most other LED regulators. It is a very cost effective electronics design. So despite what most people would like to think, that there is some "magic" going on in there, it is all very simple. Hey, if you want to make $$ with a product remember the KISS principle. There is also a certain amount of elegance in being able to implement a seemingly complex task using the simplest solution possible. /ubbthreads/images/graemlins/smile.gif

[ QUOTE ]
CM said:
Only in the L1, the circuit is mostly controlled by HC04 type inverters which can be had for pennies. It doesn't use a monolithic IC controller (like the ones from Linear Tech, Maxim, National etc.) like most other LED regulators. It is a very cost effective electronics design. So despite what most people would like to think, that there is some "magic" going on in there, it is all very simple.

[/ QUOTE ]
I assumed that too, although i didn't take my L1 apart /ubbthreads/images/graemlins/tongue.gif With a better circuit (BadBoy) the light could be much smaller /ubbthreads/images/graemlins/frown.gif

I believe the head is "dumb," meaning there are no electronics there. It's all in the body part of the light.

JollyRoger,

Yes you're right, my bad. The electronics sit between the battery and the head.

Mister T,

I don't know why Surefire didn't go with a more compact solution with the electronics. They could have had a better EDC size package if they did. The circuit, because it is longitudinal in construction, makes the light about an inch longer than it needs to be.

CM

Maybe more compact circuit designs will increase manufacturing/installation costs? /ubbthreads/images/graemlins/icon3.gif

Ok so we now know how the L1 works is the A2 similar? The circuit resistance must be very low as you get over 50 hours with the LED's in low power mode.

Is anyone planning on copying this idea for a homebuilt light?

Thanks for the interesting replys so far.

Mark

[ QUOTE ]
CM said:
Only in the L1, the circuit is mostly controlled by HC04 type inverters which can be had for pennies.

[/ QUOTE ]

Can you tell us a little more on this inverter?

CM,

Thanks for the insight, in layman's terms, into the *magic* of the A2/ L1 tail switch. I am surprised that you have not mentioned the metal sleeve present in both battery tubes. As I understand it, the resistance in the ground path is very critical for proper operation of these lights. Anodization has been mentioned and yet it seems to me that the ground path for these circuits was deemed too critical to be allowed to course through the Al of the body.

I agree with your statement of elegance via simplicity; a design goal often difficult to achieve.

- Don

- Don

[ QUOTE ]
CM said:
JollyRoger,

Yes you're right, my bad. The electronics sit between the battery and the head.

Mister T,

I don't know why Surefire didn't go with a more compact solution with the electronics. They could have had a better EDC size package if they did. The circuit, because it is longitudinal in construction, makes the light about an inch longer than it needs to be.

CM

[/ QUOTE ]

I wonder if the L1 is longer than it needs to be, intentionally. I have found that if a flashlight is too short, I don't care to use it. They just don't fill the hand properly and are difficult to activate. If the L1 were any shorter, my hand would be covering the lens when I push the switch with my thumb.
oldgrandpajack

I have to say the L1 would be a lot more attractive if it were closer to the size of an E1/KL1. That should certainly be feasible. It's a $100+ light so I don't think they need to save a few cents on a regulator chip.

If I were designing a light like this my instinct would be to use a solid "crush" type battery tube (like Arc AAA) delivering full power to the head at all times, then use an electronic switching system in the head. The tailcap switch would be a two-level resistive switch like a camera shutter release. A couple of thin wires enamelled to the inside of the battery tube would carry a signal from the pushbutton to the head so the head would know what to do.

The Arc LS4 and LS5 will work something like that, except they'll only have a one-level switch, which doesn't seem like nearly as nice an interface.

The tailcap could even have a rotary switch that signals the head the same way. Surefire is rumored to be working on something like that (maybe not in the tailcap). There was a thread about it last week. I guess we'll have to wait and see.

I have an ARC LS on my key chain, the E1+KL1 and the Ultra G. Yet, when I go out for evening walks, I carry a flashlight that is larger. It's really a matter of ergonomics. The very small and powerful flashlights are great for everyday carry and emergencies. I have and use several. I "love" them. /ubbthreads/images/graemlins/grin.gif But, if I have a choice, when I know I'll be using a flashlight for any length of time, I will pick up a larger flashlight. For example, the E2O, E2E, L4, A2, L1, MiniMag+Opalec New Beam and E2+KL1. I find that these point naturally and are activated easily. Of course I have larger flashlights, but I find that I am using them less and less over time.
oldgrandpajack

Don,

I only had the light for a few hours so I'm trying to remember what I saw. I did not notice the internal sleeve in the L1, maybe it was because I was too focused on other things about the light. But now that you mention it, I'm curious. Hmmm, I need to get that L1 back so I can inspect it some more.

oldgrandpajack,

Yes sometimes a longer light can be easier to hold. Though I carry my Arc LS 1x123TSP all the time, sometimes I just have to have the 2xAA LS when certain tasks call for it, like for example when I go out for my nightly walks where I need to have longer constant on and economy (AA's) not to mention the larger body helps absorb the heat of my overdriven LS. But overall I still prefer the single 123 pocket rocket.

LEDS As small as possible,

I did not draw up the schematic for their design due to time constraint. If you look at the LVR's that Willie Hunt designed, you'll see his signature use of HC04's in there. As I understand it, he now works for Surefire. Don't know him personally, though, other than he's prominent in the biker forums. I like the idea of using cheap HC04's. Consider he was doing this long before the wide availability of cheap monolithic switch mode P.S. controllers where he had to improvise, very cool indeed. Anyway, I'll try to get the L1 back for some post mortem work.

CM

Of course I believe the L1 could be shorter - however, I would suggest that if SureFire had the choice of:
1) Making the L1 from parts they already had
or
2) Starting from scratch

They wouldn't have made the L1 at all if they had to go for option 2 - not with 5W Luxeons being worked. Why go to all that effort? Making the L1 10mmm shorter, perhaps even 20mmm shorter would have meant not only the L1 would have been released much later, but also all the 5W products too.

Just my £0.02

Al /ubbthreads/images/graemlins/smile.gif