js
Flashlight Enthusiast
Luna,
Please don't bother hitting the ohmic question in another post. Not on my account anyway. OK? Because it really doesn't matter what the resistance of the filament is. You can always find a single voltage and current point and then use the re-rating formulas from there to determine the new current at a different voltage. It's more or less straightforward to measure the current draw of a lamp for a given drive voltage, then you just go from there. I'm not sure why you even needed it back in that "SF/M6" thread because I *DID* right from the get-go give voltage and current values for the MN21. Then you posted this, a couple posts prior to you challenging me on the re-rating formulas:
The ohmic approximation is never going to be useful. It is always just as easy and more accurate to use the re-rating formulas.
And notice that they do not have a re-rating formula for CCT? That's because the relationship between CCT and V, I, Hrs. of life, and Lumens is not deterministic. It depends on fill gas, filament geometry, envelope size, etc., etc. You can reverse engineer one from the various WA specs, but I suspect that that is probably only approximately valid for their lamps only. Because I know that the fill gas alone can have at least a 100 K effect on the CCT.
As for mirroring the underside of the lamp envelope or the surface of the potting material or support structure, I can only say for sure that you obviously have to make sure not to form a conductive path between the two lamp pins, and also that you will probably introduce some spurious light to the beam, i.e. artifacts. Plus there may be some issues with increasing envelope temperature at the pinch, as well as mating the materials together over such a large range of temperatures. It certainly can be done: I know of an Osram lamp, for example, which is meant to hang down from ceiling lumiaries and its bottom half actually IS a reflector. Pretty neat, really.
But anyway, let's just drop the whole ohmic question, OK? I mean, you aren't saying that it would be BETTER than the re-rating formula for current vs. voltage, are you? If not, then the question is really a dead-end in my opinion, FWIW. But suit yourself I guess.
Please don't bother hitting the ohmic question in another post. Not on my account anyway. OK? Because it really doesn't matter what the resistance of the filament is. You can always find a single voltage and current point and then use the re-rating formulas from there to determine the new current at a different voltage. It's more or less straightforward to measure the current draw of a lamp for a given drive voltage, then you just go from there. I'm not sure why you even needed it back in that "SF/M6" thread because I *DID* right from the get-go give voltage and current values for the MN21. Then you posted this, a couple posts prior to you challenging me on the re-rating formulas:
Luna said:js said:4.9 to 5.0 amps times 6.8 volts equals 33.3 to 34 watts.
So Brocks measurements are off ?(6.1v 4.9A giving a heated filament resistance of 0.803ohms)
Otherwise wouldn't you be seeing about 5.5A at 6.8V?
The ohmic approximation is never going to be useful. It is always just as easy and more accurate to use the re-rating formulas.
And notice that they do not have a re-rating formula for CCT? That's because the relationship between CCT and V, I, Hrs. of life, and Lumens is not deterministic. It depends on fill gas, filament geometry, envelope size, etc., etc. You can reverse engineer one from the various WA specs, but I suspect that that is probably only approximately valid for their lamps only. Because I know that the fill gas alone can have at least a 100 K effect on the CCT.
As for mirroring the underside of the lamp envelope or the surface of the potting material or support structure, I can only say for sure that you obviously have to make sure not to form a conductive path between the two lamp pins, and also that you will probably introduce some spurious light to the beam, i.e. artifacts. Plus there may be some issues with increasing envelope temperature at the pinch, as well as mating the materials together over such a large range of temperatures. It certainly can be done: I know of an Osram lamp, for example, which is meant to hang down from ceiling lumiaries and its bottom half actually IS a reflector. Pretty neat, really.
But anyway, let's just drop the whole ohmic question, OK? I mean, you aren't saying that it would be BETTER than the re-rating formula for current vs. voltage, are you? If not, then the question is really a dead-end in my opinion, FWIW. But suit yourself I guess.