My first official mod!!

My first "real" light was an LGI, then a guy at work broke my beloved LGI. Life was not good. Obtained a MAG 2 C, a length of washer hose, a bolt, some 3V CR123's, the NX05 optic from my LGI, a copper pipe cap from the plumbing section of Home Depot as a heatsink, and a nice white LS from King Kong. I used the bolt as a dummy battery, and put a 1watt 2ohm resistor in series to reduce the voltage. The flashlight works beatifully, but my calculations seem to be wrong. The original batteries I had were showing 5.8 volts. I wanted to overdrive the LS at 4.5 volts around .700 milliamps so I used the equation 5.8-4.5= 1.3 / .700 = 1.85ohm's. I put in a 2 ohm 1 watt resistor because that is the closest thing that I had. Now that it is all together I show I am only getting 3.4 volts at .790 milliamps. I put in a fresh set of batteries that metered 6.3 volts brand new, I still get 3.4 volts but now pulling around .870 milliamps!! It seems I should be well up over the 4 volt mark by about .5 or so volts! Any thoughts? Also how is the 30mm optic in a MAG light?

Increased resistance from corrosion where copper meets aluminum? I'm not saying that's what it is, just throwing out an idea. Try replacing the resistor, and check resistance to ground measured from the emmiter's neg. contact point while you have the old resistor out.

30 mm optics (Elektrolumen's) in a mag are GREAT!
In case you haven't seen the beam shots, here is the link:
http://elektrolumens.com/BLASTER/Blaster_II_Beamshots.html

Let everyone know what you find out with the voltage issue.

No resistance when measured no resistor, neg. on emitter to ground. I pulled it out of the MAG, reworked the setup and wiring and stuffed it in a Brinkmann LX. Same voltage calculations as stated above using 2 CR123's (obviously no dummy batt. in this set-up). I am guessing either my meter is busted or I am measuring wrong. For voltage I measure from the + side of the emitter and the - side of the emitter with the light turned on. (Wow that's bright!!) For milliamps I am measuring (with my meter set to amps of course) between the + side of the emitter and the light end of the resistor which was not attatched to the emitter. Correct me if I am wrong!!

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biblefreak said:
I am guessing either my meter is busted or I am measuring wrong. For voltage I measure from the + side of the emitter and the - side of the emitter with the light turned on. (Wow that's bright!!) For milliamps I am measuring (with my meter set to amps of course) between the + side of the emitter and the light end of the resistor which was not attatched to the emitter. Correct me if I am wrong!!

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I'm not following exactly what you're doing, but for sure you're not measuring current. Current measurements must be made in series. You need to break the circuit and insert the current meter so the current you wish to measure flows through the meter itself. Current is a flow, not a pressure (Voltage) which you measure 'across' something. We need 'through'.

I also suspect you're not moving the meter lead where it plugs into the meter? Almost all meters require this for high current ranges.

So, put your meter in DC amps, move the (usually plus) lead as required and insert the meter in the current path. Often an easy way to do this is to unscrew the end cap, turn the switch to the on position and put one lead of the meter on the minus end of the battery, the other on the frame of the flashlight. The light should come on when you do this (since current is now able to flow through the meter) and you should get the correct reading.

Doug Owen

Listen to Doug...elec. knowledge far exceeds mine.

It sounds like Biblefreak has broken the circuit between the resistor and the LED and IS measuring the current to the LED by placing the meter in series??!?!?

- Don

Doug; if I read him correctly then this is what he does, by disattatching the resistor from the emitter and placing the multimeter in between. He also seems to get a realistic reading if I am correct that he means 790 mA at 3.4V.

I do not understand the original question I think - were you expecting to be able to drive the volts up to 4.5V over the emitter?

Yes, I am measuring correctly, and yes, I was hoping to get 4.5 volts across the emitter. I thought that was what the resistor was for- to drop the 6.3 volts down to the rating of the emitter or what would be over-driven I guess. I think I may be wrong in my thinking. Will the emitter ONLY pull 3.5 volts? Is it just the current that goes up or down by applying more voltage? I hvae tried several configurations going down to as low as a 1ohm resistor and watching my voltage stay more or less the same, but my current varying.


edited to correct spelling!

biblefreak,

The Luxeon makes a fair zener diode because once you reach the vfd (at 350ma), it only takes ~0.1V to push another 100ma+ through the Luxeon. Basically, the voltage at the Luxeon will vary little even with large differences in current.

Also, remember that battery voltage drops under load, especially heavy loads.

You'd probably need to push over 2 Amps through the Luxeon to see 4.5V at the Luxeon......