Regulated vs. Resisted circuitry?

Saw I post indicating a Streamlight TL-2 LED having a resistor instead of being regulated. I have a idea of what the resitor would do, what/how does a regualtor work in a flashlight? And what benefits do we receive from this type of technology?

theoretical a regulation should be the best way drive a led.

but how does a regulation really works or better ask what is a regulation able to do?
i didn´t find a satisfied answer till now.

there are so many regulations out there.

look at the new surefire KL3 rev2 head on quickbeams site.
that´s what i regulation should do... but even in a 100 dollar heliotek the regulation didn´t do like this. /ubbthreads/images/graemlins/ooo.gif

There are so many open questions left. /ubbthreads/images/graemlins/crazy.gif

for example will a regulation be able to handle the different Vf bins and what is the effect?
What about the lowest Input Voltage (U) (+ current(I) the regulation puts out nearly 100% compare to fresh batteries?


etc.
/ubbthreads/images/graemlins/wink.gif

if you see these questions like i do than you know why Maginstruments is still proud on their over 20 year old lashing (is this the englisch word for this /ubbthreads/images/graemlins/tongue.gif

There are a lot of variations and twists to regulation, however, I will try to provide a simple answer.

Regulated and "semi-regulated" lights tend to give a relatively constant output until the effective end of battery life.

If the light is LED based - a regulated circuit can be designed to ensure the LED is driven at "safe" levels.

The output of non-regulated lights will gradually decay as battery voltage drops.

There are many other factors including: cost, size, ease of construction, efficiency, intended use, functions required (dimming, flashing), source vs load voltage as well as others that come into play when deciding on regulation or not. HTH,

Paul

[ QUOTE ]
Analog said:
Saw I post indicating a Streamlight TL-2 LED having a resistor instead of being regulated. I have a idea of what the resitor would do, what/how does a regualtor work in a flashlight? And what benefits do we receive from this type of technology?

[/ QUOTE ]

Just to clear things up about the TL-2 LED...the first generation TL-2 was in fact resistored. The new model is in fact regulated, and quite nicely I might add! VERY flat output for the first couple hours, and is brighter and throws better than a Pelican M6 LED. The new TL-2 LED's don't seem to get much attention here at CPF, but they're VERY good lights for the price, IMHO!

PJD

I have a first gen TL-2 LED, and haven't had an opportunity to try a new style yet.

Non-regulated, resistor-protected LED flashlights have the advantage of giving you very long runtimes on alkaline batteries, so long as you don't mind the steadily diminishing brightness. For this reason, they can be very good emergency flashlights.

Take a look at the long runtime that the non-regulated Lightwave 2100 (now called Lightwave Pro2000, I think) gets. Those tiny little horizontal divisions are hours. And this flashlight runs on three AA cells, which have a modest capacity. The Lightwave 4000, which uses D cells, can provide low but useable output after 11 days.

"Non-regulated, resistor-protected LED flashlights have the advantage of giving you very long runtimes on alkaline batteries, so long as you don't mind the steadily diminishing brightness."

Quick question about this. I have wondered about why the runtimes are so long, but never asked until now... It seems that most white leds need about 3.4volts (Vf). So, a 3xAAA or 3xAA setup gives you 4.5V, which would then require a resistor.

So, what happens when the batteries drain down to, say, 1V each? Now you have a total of 3V, which is less than the Vf of the leds. Then it keeps going down and down. But it seems like the light is still shining (although much dimmer). But I thought that the led wouldn't run at all below its Vf... I must be wrong.

Can someone explain what's happening? Is there a time when the leds finally 'shut off' completely? I've often wondered how my little Petzl Zipka headlamp can run so long on 3 AAA batteries...

LEDs run at their RATED current at Vf, below Vf they run at less current than rated. With a resistor it drops the voltage down to near the Vf at start unless you overdrive the LED then from their the current to the LED keeps dropping as the batteries are used up. Most lights overdrive the LEDs some so you get longer brightness instead of longer run in the medicro dim mode. If you look at LEDs when they seem to have gone out sometimes you can still see them shine through the lens of the LED. I am not sure of the voltage but it is well below 3v on most white LEDs.

Its a hard choice, for runtime I go for Resisterized lights
for constant brightness I go for the regulated at the cost of runtime, I usualy carry both when away.

Probably the best compromise is a multistage regulated which is basically a pseudo combination of both essentially you have the advantages of constant brightness when needed but can also throttle back the light output to a dimmer level to conserve batteries thus increasing runtime. The main advantage of resistored lights is cost. It only takes one resistor to *regulate* current to acceptable levels at a cost of perhaps a nickle or so while the cheapest boost circuits probaly run closer to $1 for single LEDs and about $5 and up for the higher output/multiple LEDs. Some of the fancier circuits can cost as much as a nice resistorized light itself.