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Gadget Freak Case #228: Super LED Flashlight Hits 3,000 Lumens
10/19/2012

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John Duffy's super LED flashlight is almost three times as powerful as xenon car headlights.
John Duffy's super LED flashlight is almost three times as powerful as xenon car headlights.

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dbell5
User Rank
Gold
Re: Go John!
dbell5   10/22/2012 2:43:50 PM
NO RATINGS
@Rudy - Hey, no problem - I love a good technical discussion! :{)


In the series/parallel arrangment John used (3x3 of 10 W originally, and I have to assume 2x2 of 20W in the parts list), both the current and the voltage divide among the 9 resistors. 1/3 I x 1/3 E = 1/9 P in each resistor. Doesn't matter a whit, if they are all in series, all in parallel, or in groups like this.

It's all a bit overkill, though. Unless I haven't had enough coffee yet this morning, dropping 2.5V at 2.5A is only 6.25 Watts. Still a bit much for a single 1 Ohm/10 Watt resistor, but should be no sweat for a single 1 Ohm/20 Watt, as in the parts list.

 

Dave

RICKZ28
User Rank
Platinum
Tinkering
RICKZ28   10/22/2012 2:24:43 PM
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It's great to read about this young man "tinkering" with stuff...nice project!  John Duffy, keep up the great work, and consider an engineering or science degree, and career!

All too often, interviewing engineering personnel candidates, I found that many young degreed engineers have never worked with/on anything while growing up (or currently).  They have not had projects building gadgets, fixing things, or modifying stuff.  They say things such as they like cars, but have never attempted any work on cars.  I wonder if they can even hammer a nail, or screw-in a screw...use a tool.  Installing software and playing video games does not count to me as a project or tinkering.

By age 18, my list of projects and accomplishments was huge, a lot of practical experience...including advanced auto and motorcycle mechanics, and Hot Rodding (modifying to be powerful and fast).  Growing up, I helped my dad with numerous house and car repairs, my dad was an engineer (now retired).

RudySchneider
User Rank
Iron
Re: Go John!
RudySchneider   10/22/2012 2:04:43 PM
NO RATINGS
@Dave ---

I don't mean to argue, but I think you need to re-think that.  If I place two 1K, 1-Watt resistors in series, I end up with a 2K, 1-watt resistor.  The same holds true for three series 1/3-ohm, 30-watt resistors, as in John's example.  It ends up being a 1-ohm, 30-watt resistor. 

If John had started with nine 9-ohm, 10-watt resistors, and placed them ALL in parallel, I agree that he would end up with a 1-ohm, 90-watt resistor.  That's not what he describes, however.

Eddy Current
User Rank
Iron
Re: Go John!
Eddy Current   10/22/2012 1:06:47 PM
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From your video we can see that you have done some experimentation with other batteries and LEDs.  Enjoyable video and it looks like you are having fun. 

What's next for you?

-Eddy

mrdon
User Rank
Gold
Re: Go John!
mrdon   10/22/2012 12:55:20 PM
NO RATINGS
Hi John,

To aid in your LED lighting research experiments, here's a cool online circuit simulation website called Circuit Lab. Nice way to do paper analysis first and then model it using software. Here's the link below. Enjoy!!!

https://www.circuitlab.com/

mrdon
User Rank
Gold
Re: Go John!
mrdon   10/22/2012 12:39:20 PM
NO RATINGS
Hi John,

I shared your Gadget Freak video with a group of  DC-AC Electronics students at ITT Tech to get them motivated about Electrical-Electronics Engineering Tech. I wanted to illustrate the importance of doing homework, which you elegantly demonstrated, in the video based on your LED research. Keep the good work!!! 

dbell5
User Rank
Gold
Re: Go John!
dbell5   10/22/2012 12:16:11 PM
NO RATINGS
Great job, John! Keep up the good work.

 

Rudy Schneider:

Huh?!?  Better go back and study Ohm's Law again, my friend!

Paralleling three equal 10W resistors will, as you agreed give you a 30W equivalent.

Placing three equal 30W resistors *however achieved* in series will indeed give you a 90W equivalent. If all nine resistors are of the same value, the combination will have the equivalent resistance of a single resistor, with nine times the power rating.

 

Dave

RudySchneider
User Rank
Iron
Re: Go John!
RudySchneider   10/22/2012 11:50:24 AM
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Just a quick correction, John...

You are correct that three 10-watt resistors in parallel will make a 30-watt resistor that is one-third the resistance.  But then adding three of these 30-watt resistors in series will only result in a resistor of the original value, but STILL only capable of dissipating 30 Watts, not 90W as you stated.

Fklein23
User Rank
Iron
Re: Go John!
Fklein23   10/22/2012 10:09:48 AM
NO RATINGS
John: I am impressed with your results and would like to talk to you about your future. My name is Frank Rudolph and you can reach me on Linked-In under that name. You can reach me on Linked-In or directly at docrudolph@gmail.com, or at rudolph@beaconpower.com. At Beacon Power, our corporate charter focuses on alternative energy and sustainability.

Incidentally, if you don't already have a Linked-In account, you should get one now!! Judging from what I have read here, you have a brilliant career ahead of you, and making contacts with a network of people in the industry should start for you right now! Good job! Keep on thinking of new stuff.

 

laserdudephil
User Rank
Iron
Nice work John
laserdudephil   10/22/2012 9:36:09 AM
NO RATINGS
You're clearly well on your way to an elustrious career in electrical engineering.  Do take a look at the ol' LM317 (LM117,217,317) voltage regulator datasheet.  Somewhere in the back is a constant current regulator circuit that you will find very useful in your line of research.  Also, check out Natsemi's (now TI) boost switching regulators.  Just add an inductor, a FET, a diode and a bunch of caps to nake a voltage step-up constant current regulator.  I just finished a controller design to drive those ebay 100W modules (33V @ 3A) off of 12V power.  Keep having fun.

-Phil

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