A couple of observations on the Tek-tite Excursion. Not many posts exist on this flashlight probably because it is a pretty expensive 3 D-cell unit, but it has its good points. The body is one single piece of turned aluminum which is hard and heavy. For tactical uses it is very good for bopping someone if shining a bright light at them doesn't work. There is no switch, so the turn-on uses threads to push a gimmiky Star LED board against the aluminum case. It is not an inspiring arrangement, but has worked for home uses no problem. Here is the general idea:
What I have to ask is...what is the little black box glued to the side of the lens? It has 2 small cylinders of something inside the box, non-magnetic, almost like it is a focusing device. Except that when can a magnet focus a beam of LED light? Did I miss this chapter in the physics book?
Anyway, a couple of years have gone by since the original Luxeon Star emitter was used. Now we have emitters capable of providing a whopper of a beam, albeit at about 4 hours time limit. The second question is then what is a reasonable operating current for the Cree XML2 that I'm going to use? Mainly the answer depends upon what you think a safe operating current for a D-cell might be. Right now, it runs fine right at 1 amp and I'm hesitant to ask a D-cell to provide more than this.
The spec sheets on common D-cell batteries are really interesting and help a lot with this planning. I have to ask another question and that is one about the difference between efficiency and efficacy. As an engineer, I like the fact that the newer emitters turn on at lower and lower voltages. That means that even a 2 D-cell flashlight might be OK with a high power emitter that previously would take 3 cells to turn on. However, using a reasonable 1 amp current draw from the cells means that I have to use larger current limiting resistors. It might be a wash. Previously the extra heat might have come from the emitter itself, whereas now for a given one amp draw, the spec sheets say I get more light output. Now some of that heat that was originally aging the LED emitter is now transferred to limiting resistors. That's a good thing since the lumen output of the emitter should theoretically be extended. So...you can get more light output for the same 1 amp battery draw and that's an increase in efficiency as I see it.
But what about all the advertising copy that claims "efficacy" is the deal? It appears to me that efficacy is largey an advertising code word for what might be possible under specific ideal conditions. Fine, I suppose we might want to know that number but I find it largely useless for making practical flashlights. Meanwhile I wonder if someone is making a sturdier star emitter holder unit that doesn't rattle around inside the head of this Excursion. All in all, a good heavy flashlight especially with the rated (currently) 250 lumen output using a CREE XML2.
King7
What I have to ask is...what is the little black box glued to the side of the lens? It has 2 small cylinders of something inside the box, non-magnetic, almost like it is a focusing device. Except that when can a magnet focus a beam of LED light? Did I miss this chapter in the physics book?
Anyway, a couple of years have gone by since the original Luxeon Star emitter was used. Now we have emitters capable of providing a whopper of a beam, albeit at about 4 hours time limit. The second question is then what is a reasonable operating current for the Cree XML2 that I'm going to use? Mainly the answer depends upon what you think a safe operating current for a D-cell might be. Right now, it runs fine right at 1 amp and I'm hesitant to ask a D-cell to provide more than this.
The spec sheets on common D-cell batteries are really interesting and help a lot with this planning. I have to ask another question and that is one about the difference between efficiency and efficacy. As an engineer, I like the fact that the newer emitters turn on at lower and lower voltages. That means that even a 2 D-cell flashlight might be OK with a high power emitter that previously would take 3 cells to turn on. However, using a reasonable 1 amp current draw from the cells means that I have to use larger current limiting resistors. It might be a wash. Previously the extra heat might have come from the emitter itself, whereas now for a given one amp draw, the spec sheets say I get more light output. Now some of that heat that was originally aging the LED emitter is now transferred to limiting resistors. That's a good thing since the lumen output of the emitter should theoretically be extended. So...you can get more light output for the same 1 amp battery draw and that's an increase in efficiency as I see it.
But what about all the advertising copy that claims "efficacy" is the deal? It appears to me that efficacy is largey an advertising code word for what might be possible under specific ideal conditions. Fine, I suppose we might want to know that number but I find it largely useless for making practical flashlights. Meanwhile I wonder if someone is making a sturdier star emitter holder unit that doesn't rattle around inside the head of this Excursion. All in all, a good heavy flashlight especially with the rated (currently) 250 lumen output using a CREE XML2.
King7
