Nuwai TM301X-3 downboy question

Please help a modding newbie: After modding my QIII-mother with some minor improvements I would like to get into regulated lights. I read in some threads that you can put a downboy converter into this light.
The question: does it fit right into the aluminum hestsink? Whats the approx. height of the converter as I already put a copper-penny heatsink under the star. Will it go under it?

Thanks a lot for your help!!!

There is plenty of room for the downboy convertor board in the space between the star and the battery contact board. The penny shouldn't make much of a difference. For an even better heat sink solution, consider potting the convertor board in thermal epoxy or JB Weld, completely filling in the space between the star and the battery contact board. I haven't done that myself, but it seems like it would be a good thing to do.

Yes I change board to DB500 and put 60 ohm in two stages switch. It's go on pretty cheap good one.

Thanks for the help, I think I´ll order one soon. Something came to my mind: do I have to change the resitor in the two-stage talicap or does this not influence the converter?

I'm not sure stock resistor in tailcap is suit for use or not. I use 60 ohm with 123a*2 and it show low nice light for me. If I use R123a*2, 8 V. light level in resistor stage will give more bright. If I use 1*R123a or 17670 battery light was a little dim in resistor stage.

Do you guys know how to modify the light in step by step instruction?


I'm new at it, and I don't know what to do since I've ordered my 3.6x2 rechargable (protected).

I would like to use on the 2 cell 123 version.

Which one should I buy? Any direct link?

THANKS!

With your improved heatsink and a some heatsink compound applied between the outer round surface of the heatsink and the inner surface of the flashlight tube you could use a DB 1000 for maximum light output.

A DB 1000 will run a bit more than an hour continuous on a set of 750-800 milliamp/hour (mah) recharcheables.

I wouldn't use a 2 way switch with a Down Boy because the lower voltage would just cause the converter to fall out of regulation. There are converter boards that will allow for regulated high/low operation but the lower priced Down Boy wasn't designed with that feature in mind.

Something to note is the small size of these converter boards. They are smaller than a dime. You need to think a few steps ahead when working with them for the first time. A small clamp to hold the board while soldering the wires to it will greatly reduce the frustration level and a very fine point tipped soldering iron is a must.

There is plenty of great info and photos at The Sandwich Shoppe

Thanks for the information. But If I can't use the DB then what is the simplest way for me to use the 3.6vx2 rechargeables?

Thanks

Somebody, please correct me if I'm wrong but I recall the Q3 Mother uses a simple resistor in line with the luxeon to drop the voltage from the batteries down to a level that's safe. If this is the case, then to go from regular 3 volt CR123A cells to rechargeable 3.7 volt cells might only require you to increase the resistance to a value that doesn't allow more than a safe amount of current to flow through the luxeon star.

I would use a digital multimeter set on a current scale of 1.5 amps or higher and test the current going to the luxeon star by removing the tail cap and touching the tip of one test lead to the battery while holding the tip of the other test lead onto the threads on the outside of the flashlight tube.

If you get a reading of more than 1.000 amps (1000 milliamps) with freshly charged-but not hot off the charger rechargeables then you will need to increase the resistance to a level where 1 amp or less is flowing.

If you know how to use a soldering iron then changing the current limiting resistor should not pose a too much of a challenge.

The up side of all of this is that if you do have to change the current limiting resistor then you get the opportunity to set the luxeon star's drive current to what you want it to be. You could dial it back a bit and be conservative or ramp it up over 1000 milliamps for some overdriven maximum brightness.

Wow that's all great, but I don't know electronics, I do have a digital multimeter, but I don't know how to increase the amp of the circuit.

I suppose I will research how to do that....

You need to use what is called Ohm's Law . If you google it you will find some very easy to use automatic calculator pages where you just type in the values you know like your battery voltage and the amount of amps your meter measured and you will get the total resistance of the circuit.

Ohm's Law states that resistance is equal to voltage divided by current (measured in amps) so for your setup, lets put in the numbers like so: Voltage (3.7V x 2=7.4V) divided by current (1.000 amps) gives us 7.4/1.000 = 7.4 ohms of total resistance in that circuit.

Lets see what we get for .700 amps (700 milliamps) 7.4 volts divided by 0.700 amps = 7.4/.7 and that gives us 10.58 ohms of total resistance in that circuit.

The luxeon III will have a resistance of a bit less than 1 ohm so you will need a voltage drop resistor of 6 to 7 ohms to run your lux III up around 1.000 amp of current and a 9 to 10 ohm resistor will get you close to the 0.700 amp mark.

There is always some variation with batteries and resistors so the easiest thing to do would be to buy enough resistors (they are very inexpensive) to give you several different values between 5 and 10 ohms. Once you have the resistors you can try out the different values to see how much current is best for your needs.

If you let more than 1.000 amps flow you will be overdriving the lux III and it will generate more heat.

If you don't have good heatsinking, running a lux III beyond 1.000 amps is not a good idea. Sure, it will be brighter, but at the expense of more heat and less run time on a set of batteries.

I ordered a downboy 750 from the shoppe. Maybe I can take some pictures while installing it.

Concerning changing the resistor in the head: I found out that there seems to be a resistance of about 0.8 ohm in the tailcap at max. brightness. I am not sure if this i the case with all the tailcaps, but you should measure that before calculating the proper resistor.

Resistor in Body?

when using any kind of electronics (like the Downboy), shouldn´t one get NO ohm at all in the circuit batteries <-> converter <-> LED ?

If any resistor to use, then the one on the Downboy itself, maybe with a switch to change illumination levels.
(...does not apply to fixed output converter)

There is no problem using a resistor in the tailcap to force a low output mode when using a Downboy as the LED driver. Of course the Downboy is no longer in regulation, but that doesn't really matter very much - you still have your low mode and a very extended runtime. It would of course be nice to have a Downboy board that gave two regulated currents, but mostly that would just get you extra runtime on low, and you already have quite a bit of runtime when you use the existing Downboy and a current limiting resistor in the tailcap.

If you do use a Downboy and 2 CR123 or R123 cells, a 30 or 60 ohm tailcap resistor will give a low "low".

@ yellow: I know there should be no resistance in the cicuit at maximum brightness, but there is some and I´m pretty sure it comes from the tailcap. I think I´ve read similar things about the kroll switches or the switches in a stock maglight.

@ wasblinded: thats exactly what I thought. I dont care about the unregulated low level as long as the high level is regulated. I´m really looking forward to see how it works

I have one modded by MilkySpit with a UX1L and a DB1400 (or maybe 1200), S020XA, UCL and the two stage tailcap.

It works great and is quite bright on full power on R123

I originally tried R123 in it stock and it melted the solder on the resistor in the head in a few minutes!

NetMage said:

I originally tried R123 in it stock and it melted the solder on the resistor in the head in a few minutes!

Click to expand...

Same darn thing happened to me, I used some silver bearing solder (Stay Brite?)
to re-solder the resistor, and Arctic Alumina all around the resistor and cavity to wick the heat away and so far so good with R123's, it will get rather warm on a long run though.

NetMage said:

I have one modded by MilkySpit with a UX1L and a DB1400 (or maybe 1200), S020XA, UCL and the two stage tailcap.

It works great and is quite bright on full power on R123

I originally tried R123 in it stock and it melted the solder on the resistor in the head in a few minutes!

Click to expand...

And I thought mine would get bright with a downboy 750......;-)

Do you have any photos of the installed converter or is it potted in some thermal epoxy?