Brocks Led Review "PT Attitude droping resistor"

Numbers

Enlightened
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09-23-01 Attitude from Princeton Tec. This is a nice little light. It is completly waterproof to 500 feet so it can be used as a backup dive light. It uses the same body as the rage, another 4 AAA light using an incandessant lamp. It uses a droping resistor to "waste" the power from the 4th battery since LED's really only need 3 cells to run normally. The light is made pretty well and is a good LED light and it isn't too expensive.

Could someone (brock?)clarify this statement for me?
Does it mean that there is no benefit of any kind to having the fourth battery? Are Attitude users literally buying the fourth battery to throw it away because the light "wastes" it? For best effeciency should led lights be bought only in three cell configuration?
Thanks
 

cave dave

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but that's not as bad as the Inova X-5 which uses a resistor to waste away 2 volts of Lithium battery power. Ouch!
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$$$
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I've thought about putting in a smaller resistor and using a dummy battery. Anybody tried this yet?
 

lambda

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Yes, and No. Dropping resistors have their place because as more batteries are used, the higher the voltage. The resistor advantage is that its resistance is fixed; as the batteries loose power, the voltage goes down, so does the voltage dropped by the resistor (varible voltage drop). When alkyline cells get to 0.9V, they're pretty dead; 3 cells - 2.7V, 4 cells 3.6V.

You got it, the one with four cells will still light the LED, where the one with 3 will not. No, it's not as good a solution in most cases than a DC/DC converter, but in some circumstances, it works quite well.

Hope I've made some sense; you can always play with both, I have, and learned there is a time and place for everything........
 

papasan

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that would be nice if the LEDs drew the same amount of current throughout a wide voltage range...since their current draw goes down as the voltage does (same as a 'fixed' resistor) you still lose in the end...

it's not *exactly* like wasting a battery, you will get a little more run-time out of it, but it's not the best solution...only the easiest one...

now i would think that 4 AAAs have enough internal resistance to power 3 LEDs without a resistor...of course you'ld be puching the LEDs pretty hard at least for a little bit...
 

Brock

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cave dave are you sure there is a resistor in the X5? I would also guess there is one, but since the light will run with one 123 cell and a blank cell I would think the voltage would be to low with a resistor. But at the same time two 123's would almost certainly fry the LED's?

Numbers, it does sort of waste some of the power, but as others have mentioned it is still going to run longer then 3 cells, and since PT already had a 4AAA light it only makes since to go this route.
 

pec50

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You might want to also consider purchasing the Rage lamp for the Attitude. It will give you option of swapping the LED assembly for a fairly bright xenon lamp assembly; and it does use the fourth battery
smile.gif
 
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