Help with Fatman and Tri Lux

I am trying to build a Tri Lux using modamag's perfect tri sink and a Fatman driver. I am trying to use 123 Batteries, ideally 2 or 3. I can get the stars to light up with the (3) 123's but not through the Fatman. I am not using an external POT. When I use a multimeter, I measure ~35 volts but it quickly drops to ~ 7 volts. My multimeter won't measure current higher than 200 ma so I can't measure the current. What am I doing wrong? Any help is greatly appreciated.
Thanks,
Chris
.308

2 CR123s likely won't be enough to run 3x Luxeon IIIs at full power. 3 ought to suffice.

How do you have the meter connected to get the short 35V spike? If you have it in series, you'll get some strange readings - a voltmeter needs to be in parallel with the load.

I don't have enough information to begin to help you with the fatman. I hope you never powered it on without the load (Luxeons) connected - I don't know if it's open-circuit tolerant.

Thanks idleprocess. I used (3) 123's and it lit up. Anyone have any suggestions/recommendations for adjusting the Fatman for maximum brightness without a multimeter?
Thanks,
Chris
.308

There might be some tricks to approximate current with a voltimeter, but I'm not familiar with them. You could also try about 5 identical loads in parallel and hook up your 200mA current meter in parallel and multiply the current by 6 ... but I'm not sure if that would be accurate - not easy to simulate a chain of diodes with resistors.

You could use a resistor in place of the pot with a value that corresponds to your preferred maximum brightness and set the onboard trimpot to maximum and assume that the current regulation works as advertised.

Thanks once again idleprocess. I went back and checked the technical details for the Fatman (always a good idea to read the instructions) and it gives resistance values that correspond to current. I measured the resistance and adjusted the pot to give me ~ 1000ma.
Chris
.308

1. Are your luxeons wired in series or parallel?
2. Did you double check your wiring of the fatman with the diagram from his site?
3. Did you make sure are connections are soldered correctly?

The best thing to do is go out and buy a better multimeter. Why risk frying your fatman and the lux(s). Since your making flashlights now, your gonna find you'll need it later too. Go to radio shack and find one that's for sale.

3 lux 3s in series is the way you want to run this combination.. the fatman is a baddass driver for the job too.. put on an external pot or better.. a multi through switch with a few specific resistors for hi med low or something.. get your milage from the driver.

as somebody else mentioned.. hope you didn't try to run the driver w/o a load.. make sure you put the emitters all in series pos to neg to pos to neg..

to do a guick test you should be able to direct-drive the lights.. which it sounds like you did.. 3 series 123s should lite them up..

at 1000mA you'll need about 3.75W x 3 or 11 1/4W output.. adding in the driver efficiency factor.. that would be 13W. Divide by 9V to get 1.47A.. that is VERY HIGH for a 123 non rechargeable.. pretty much the absolute max you can do.. you'll probably have a lot better luck starting at 700mA.

did you measure the battery voltage when attempting to drive them?

-awr

PS.. using an ohmmeter to preset the current using george's method is definitely the best way.. it's extreeeemly accurate to do it that way.. usually within a couple mA

Thanks for all the answers everyone. The lux III are wired in series and everything looks fine now, but I am interested in optimizing my setup. andrewwynn do you have a link for the type of switch you mention? Also you mention the 1.47A as very high, excuse my ignorance here but is that bad for runtime for the 123's or what? any info or help other than telling me to give it up /ubbthreads/images/graemlins/smile.gif is greatly appreciated

the 123 can handle just about 1.5A maximum.. but at that current drive you are waiting 1/2 your energy heating the battery.. it really clobbers the runtime since 1/2 the stored energy is just blown.

the type of switch i'm talking about is exactly what is used in the VIP.. a 'SP3T' switch.. a common lead that swiches to 3 different connections.. if you have a switch like this and it can be rotary or slide or whatever.. you can calculate the resistance you need for 3 or 4 (or 8) different levels you would like.. and wire up resistors to connect to the fatman's 'pot' input loop.. you want to use a 'logarithmic' curve for your brightness.. for example.. if you start with 1000mA.. multiply by .75 to get to 750 for the next level.. and multiply again by .75 to get 563mA.. etc.. my latest setup has 8-levels.

primary 123s are pretty expensive.. even if you buy them for $1.50.. that's $4.50 for about 40 minutes at full power.. i recommend LiONs for such a monster.. like the 18650 battery.. 1/3 of a penny to recharge and you can get.. 13W/3.7V = 3.5A.. oops better use two of them.. 1.75A.. you'd have 2400mAH / 1750mA = 1.37 hrs and it would cost about 1/2 a penny to recharge.. maybe 2/3.

That's how i'd do it.. what is the holder? (diameter and length).

-awr

Thanks for the help andrewwynn. Are you talking about Pila batteries or are there others that are more reasonable? I think Pila's are pretty expensive (not saying they aren't are worth it). I think I would want an extra set of batteries, so 4 batteries plus charger would be over $100. I am using a 5/8" i.d cpvc sleeve that is slightly shorter than the three 123's.
Thanks,
Chris
.308

i would build my own battery pack from battery space batts.. it would be like $20 for two 18500s and $7 more for the safety circuit. i think you might need a charger too and they sell them as well.

if you can fit 65mm in the sleeve.. get the 18650 bat.. 2400mAH.. that is 2x the pila that i have.

pilas are good.. they have the protection ckt built in.. but you will be installing your own.

-awr

Where can the safety circuits be had and is there a part number? Is it hard to install it? Any help is much appreciated.

i think it's www.batteryspace.com

I´m using two 18650 in my Trilux (Mag 3C,Fatman@1A). The Cells have only 1850 mAh capacity (ripped from a camcorder battery /ubbthreads/images/graemlins/wink.gif ), but it works well. The Fatman draws ~1.45 A.

btw, what is a "common" limit for max. discharge current of a 18650 cell? something like 1C or less?

I´m using the original protection circuit of the pack, but the circuit seems to have only under/overvoltage-protection and don´t prevent too high discharge currents. I made a short test with different resistors and easily got more than 3A without (immediate) problems.

most bigger batteries can handle 2C.. which means you can pull well over 2A.. i presume they are in series? 3 to 3.5A would be ok.. the closer you are to 1C the less wasted energy heating the batteries.