Talk me into building a Direct Drive...

So my brother now wants me to convert his Mag 3D into a LuxIII thrower - no problem. However, now that I've got some boards and experienced regulation, I've convinced myself to run 4C in his light driving a TW0J behind a DB1000. Can someone please remind why a simple TW0K DD mod would be better and save me some time this weekend?

I say stick with the regulation. DD in that configuration is asking for trouble. Better to take a little more time and do it right, and build a reliable regulated light, than risk blowing the LED sometime later down the road.

Looking at my own old post, on a 3D M*g I would recommend a simple DD with a 1ohm resistor:
what I am giving away for father's day ...

Will

Efficiency.

DD = Lower Cost & ease of mod. You'll spend as much for a led driver as you will on an o-sink and a Lux-III. Drivers = more connections = more time to build = more chances for things to go wrong.
If I was going to use a driver, I'd want it to offer something like multiple output settings like georges80 nFlex driver. It gives (7) brightness settings.
Good Luck,
Chris
.308

Just put in a resistor, maybe 1 ohm, just to be on the safe side.

Also check out modamag's DD ref sheet Direct Drive Reference Sheet. If you can you may need to go to a TW0L or TW0M. If you are going to use rechargeable Nimh C or D batteries then a TW0K should be fine. Or like Former Mag User said put in a resistor. There is a handy calculator on this site to help determine the resistor needed.
Good Luck,
Chris
.308

The last 12 lights I've built, (including three 3 cell M*gs with Luxeon IIIs and a 5D with a Luxeon V - VX1T) are direct drive conversions with NO resistor, using TX0K and/or SYAKs, running off of regular alkalines.

No problems on any of them... Although they ARE massively heat-sunk, and I haven't tried any endurance tests with them yet.... Just "normal use"

And my current project is a direct drive TXOK off of Lithium Polymer.

As you might assume, I'm a direct drive advocate. Sure, my light might dim a little as time goes on, but I'll have SOME degree of light long after many regulated lights go dark..

Less expense to build, less space required, easier wiring, fewer components to go kaput on you; therefore more reliable.

Give me brute force over something fancy and sophisticated every time /ubbthreads/images/graemlins/wink.gif

And if the "big one hits" my DD lights are a little more likely to keep on shining.... All I have to worry about is the LED itself. No inductors, ICs caps and resistors to fry in the pulse.

don't do it! don't do it! don't do it whatever you do.

i've seen and used and built some incredible DD lights.

MY lights that i'd sell are ALL regulated.. i believe it's the best and for me only way to go for anything other than 'quick and dirty' one of the most amazing things about an LED light is the ability to use a regulator to have non-dimming brightness.. incredible.

one of the best DD lights of ever.. the tesla 6.. runs off of either 3x168 pilas or 9xAA in series.. has two strings of 3 TYAK emitters in series.. and it really rocks.. but output will go from like 7500 lux fresh bats to about 3000 lux over the runtime of 40 minutes or so.. still is a lot of light..

compared to the RT4 using the same exact battery psck.. i get 9000lux when the battery is full.. i get 9000 lux when the battery is 98% empty.. i love not having to keep charging batteries to get full blast.. i also like not ecessivly over driving the emitters.

The RT4 uses 4 ubin emittesr in 20IMS.. the tesla 6 uses 6 Tbin emittesr in 17IMS.. estimates for the RT4 using T bin lux 3s is about 6400..

the tesla six would probably hit 6400 in about 5 and certainly less than 10 minutes.. and pulls about 20W to output that kinda light.. a quad lux 3 that outputs 6400 lux would probably be about 16W and using a fatman driver it'll hold that brightness 'til the batteries died.

so.. easy quick and blinding starting light.. or not much more difficult.. megabright nonetheless and constant brightness through battery discharge.

-awr

DD is like self regulation, as long as you are sinked properly and dont go WAY over in spec.

the self regulation part works like this.
Just charged, near a charger, fresh batteries , major power .
Forgot to charge, no where near a charger, batteries low, major runtime .
only thing better than that is a driver that adjusts, and then it better do so efficientally.
and i hear that most drivers dont slow down automatically when your at the end of your available resources.
CHEEEEEP.

.308 L bins are great for 3D DD. I have made a few DD 3D m@gs with TX1L. fresh batts are about 1100mA. Granted I used hotlips and a fair amount of thermal paste inbetween. If I get another commission for another 3D, it is probably going to be used for longer periods (someone in theatre), I will be putting a 1ohm in-line with that one.
If you have the extra money, go with regulation, nflex with dimming and auto shut off I would recommend. otherwise DD all the way. /ubbthreads/images/graemlins/grin.gif
Jeff

The main caution is that 4 x C has the potential to be a little "hotter" running that even 4 x D cells. This comes from the "often" lower internal resistance of the smaller diameter cells.

I have blown a number of TWOKs attempting to DD, but usually, that was because I was not heat sinking well enough (ok - some of them were actually not heat sinked at all /ubbthreads/images/graemlins/smile.gif )

1 - 2 ohms will work wonders for balancing out your light. I borrowed a Lux meter from gadget lover for some tests, and heat reduces output VERY fast above 500 - 700ma, even for a reasonably well made light. I have the unpleasant experience of watching an 1100ma driven TWOK on a meter drop down to the same Lux reading as a 500ma driven setup within 45 seconds. Of course, the "quick on" brightness was higher.

heat kills.. but also wounds :-D

found out the hard way that a hard-driven lux will die in seconds if it comes loose from the heat sink... also found out.. that in the RT4 case.. i get more light out operating at 1100mA than 1300mA.

if you want inexpensive quality output.. use LDO.. http://ldo.rouse.com is a link to the cpf thread for a kick-butt LDO that Mr Al designed to help me with the nano.. i've used them to control as much as 1.5A and as little as 1.0mA.

-awr

If you have a choice, regulation is the way to go. I always like to keep things simple, in the battery department and usually prefer not to have to use any sort of battery adapter. For a 3D light, you could use a Wiz2 board from the shop. If you want to go with the 4Cs, then go with the Downboy that you mentioned.

With direct drive, there are just too many variables to have to keep in mind when building it. If you are going to DD the light with the 3 D cells and you are only going to be using alkalines, then a K or L Vf will do nicely. If you are planning to run NIMh cells, then you might want to go with either an L or M Vf.

My personal favorite for Mag mods is a 2 cell light with either a NexGen or MadMax converter. It keeps things really simple.

Heat shouldn't be much of an issue, if you are going to be using an o-sink or a hotlips. As a practical matter, I don't worry to much about frying luxeons after hundreds of hours of use. They're easy enough to replace.

I do have to admit though, that I built a bunch of 3D mag mods for some probation officers that I know. They do a lot of night work tracking down those that don't want to be found. I went direct drive just to keep the costs down. The guys down here have to buy their own equipment and they don't make much. They use their lights a lot and I haven't had any come back. I used K Vf luxeons in them and they drive them with alkalines.

DD is ok when you know the voltage/amperage will be within reasonable limits. Throwing a small resistor in will help too if you need to limit some current. But times when say you had a TWOH, you would not want to DD, or use a resistor as it would burn up a ton of power limiting that big of a voltage difference. There you would want to use a buck circuit.

DD can be perfect with a K VF and 3x NiMH. Even the varying Vf will be ok.

K on alkalines is iffy. If it's at 1amp or more on fresh alkalines, reduce the current some, as over time it will go up as the Vf drops and settles. If it's under, don't worry, it will go up with use.. (current that is, as Vf goes down)