FlexiLED reading/bedlight

georges80

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I had a request to assemble a flexiled into case.

First pic shows the unit about to be closed up. I attached the uFlex driver with some double sided foam. The jack on the side allows DC to be provided externally and disconnects the batteries during that time. DC can be from a wall wart or automotive 12V.

task1.jpg


The next picture shows the back of the case - with the 4AA nimhs installed. A lid then slides and clicks in - nice case. uFlex is set to one of the dim levels to not blind the camera.

task2.jpg


And the last picture shows it all finished and turned on.

task3.jpg


With 4 nimhs the light should run for at least 5hours at full output and of course a LOT longer if dimmed down a level or two. In nightlight mode it should run for a few hundred hours.

george.
 

jtice

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Really nice.

MAN, thats a really nice circuit.
I need to get together some funds to get a few more of those, I have at least 3 projects in mind for them.


Nice work. /ubbthreads/images/graemlins/thumbsup.gif
 

Illuminated

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Very Nice, George!

The uFlex is so cool - I'm getting close to having my waterproof 4AA backpacking lantern done using your uFlex driver. Can't wait 'till it's done...

[Edit - Have you ever done a runtime test using 4AA alkalines? I'm curious...]
John
 

georges80

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[ QUOTE ]
Illuminated said:
Very Nice, George!

The uFlex is so cool - I'm getting close to having my waterproof 4AA backpacking lantern done using your uFlex driver. Can't wait 'till it's done...

[Edit - Have you ever done a runtime test using 4AA alkalines? I'm curious...]
John

[/ QUOTE ]

No, I've never tried a runtime test on alkalines. It should give a pretty decent run for the money - since it is a switcher and a down converter - so it's not pulling huge current from the batteries.

Of course the moment you start to use the dimming feature - then any battery life measurement becomes tough...

And it also depends on whether we're talking 400ma, 500mA or 750mA into a Lux1 or Lux3. The higher the current pulled out of the alkalines the less life you will get just due to the relatively high internal impedance.

george.
 

Illuminated

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Thanks George,

I know that runtime jumps when using dimmer settings - I was just wondering what I could expect from 4AA alks at full brightness driving one of those Q2H 1-watters.

BTW, The two Q2H's I bought with my uFlex seem to have very good color - I like 'em a lot.

Great products - Thanks again George...

John
 

Darell

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Sweet! /ubbthreads/images/graemlins/thumbsup.gif Even some extra room for spare change in the box. /ubbthreads/images/graemlins/smile.gif
 

georges80

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[ QUOTE ]
Illuminated said:
Thanks George,

I know that runtime jumps when using dimmer settings - I was just wondering what I could expect from 4AA alks at full brightness driving one of those Q2H 1-watters.

John

[/ QUOTE ]

Ok, decided to sacrifice 4 AA Alkaline Maxell's (about a yr old, new in package). Below is the runtime chart. This is with a light just like the one built at the top of this post. The uFlex is a standard production unit configured for a nominal 380mA output and has a Q2H Luxeon.

The batteries ran for 5 hours and 20 minutes (320min) with the uFlex in full regulation at full brightness. You can see the 'knee' in the curve at 320 minutes where uFlex went out of regulation and into direct drive. I gave up running the test at 6 hours - the light output was at around level 3 (level 7 brightest).

I'm actually quite impressed with the runtime /ubbthreads/images/graemlins/grin.gif

runtime.gif


george.
 

Illuminated

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George,

Thanks so much for going to the trouble to do this test. That is excellent run time on high output, and it can only get better at lower levels. Lithium AA's could do still better if needed, or maybe in the cold.

I just finished my lantern project Sunday evening, and I have to say that the uFlex is coolest and most useful thing for this type of application I've ever seen! This thing is bright, and allows dialing down to just what is needed for the task while preserving power (and night adaptation).

Now, I'll have to get another...

Thanks again!

John
 

georges80

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[ QUOTE ]
Illuminated said:
George,

Thanks so much for going to the trouble to do this test. That is excellent run time on high output, and it can only get better at lower levels. Lithium AA's could do still better if needed, or maybe in the cold.
John

[/ QUOTE ]

The Lithium AA's should definitely add some hours - looking at Eveready's datasheet shows it to have a much flatter and higher voltage discharge curve. Since uFlex implements a switcher - the higher input voltage will translate to lower current draw - thus extracting more time out the the mAHr rating of the battery. Send me a set and I'll run a test for you /ubbthreads/images/graemlins/grin.gif

For lower output the battery life will be extended quite dramatically. To give you an idea - the current levels of the uFlex are listed below.

Level Current
7______100% Full Brightness
6_______69%
5_______46%
4_______30%
3_______19%
2_______10%
1_______ 4%
0______low! Nightlight

So, the battery life at level 5 will be more than double. Also at the lower levels the current draw is less and so you will get some extra battery life since primary cells have relatively high internal resistance and are less efficient at higher current draws.

george.
 

Darell

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George -

You should go a step below zero so we can charge the cells when needed. /ubbthreads/images/graemlins/wink.gif

The runtime is truly awesome when you consider how bright it is running, and that backing off just one level will substantially extend the time. /ubbthreads/images/graemlins/thumbsup.gif
 

georges80

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And the same uFlex and Q2H this time with 4 brand new AA 1.5V Lithium Eveready cells. Thanks Illuminated for funding this 'test'.

12 hours before falling out of regulation - very impressive! Pity those lithiums are so expensive.

runli.gif


george.
 

Sigman

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Any thoughts about selling some of these to us uncoordinated CPFers? /ubbthreads/images/graemlins/grin.gif
 

georges80

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[ QUOTE ]
Sigman said:
Any thoughts about selling some of these to us uncoordinated CPFers? /ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]

Yes, I've built up a few now and folk love them. I will order some more of the cases in the next few days. Have the integral 4 AA battery holder built in is very nice and the base is big enough to be very stable with the head in any position.

PM me if you want to discuss pricing etc.

george.
 

milkyspit

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George, that's very impressive runtime with 4AA lithiums. Any thoughts on that sharp voltage drop in the first 45 minutes or so of operation? Seems a little odd given the fairly flat curve afterward.

Also -- and please forgive me if you've already explained this before -- I notice in my 4AA uFlex light that I seem to have lost some of the original 8 brightness levels. I'm down to 4 at present. Would that be due to the batteries discharging to the point that the higher levels can't be supported, and the board somehow locks them out?

(To all who haven't tried George's uFlex board, you might want to get one! They're easy to wire and great fun to use. Definitely a good buy for a flashaholic!) /ubbthreads/images/graemlins/grinser2.gif
 

georges80

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[ QUOTE ]
milkyspit said:
George, that's very impressive runtime with 4AA lithiums. Any thoughts on that sharp voltage drop in the first 45 minutes or so of operation? Seems a little odd given the fairly flat curve afterward.

Also -- and please forgive me if you've already explained this before -- I notice in my 4AA uFlex light that I seem to have lost some of the original 8 brightness levels. I'm down to 4 at present. Would that be due to the batteries discharging to the point that the higher levels can't be supported, and the board somehow locks them out?



[/ QUOTE ]

The initial drop is probably faster than the curve. I connected fresh batteries and then took a measurement a minute or so after. The next measurement was after about 1/2 hour so the graphing software just connected the dots. The open circuit voltage of most batteries is higher than the loaded voltage and that's why you would see an initial drop.

The lithiums are very impressive - they are rated at 2900mA AT 250mA draw - so they do VERY well in high current applications. Pity they are also as impressively expensive.

Yes - the apparently lost levels is due to the batteries running out of oompf. uFlex will go to 100% duty cycle which is essentially direct drive when it can't maintain regulation at the higher current draws. The lower levels require less battery current and so the battery voltage will climb enough to allow the uFlex to maintain regulation and still provide levels. That's why the higher levels appear to be lost as the batteries are close to discharged. At the nightlight level the draw from the battery is only a few milliamps so it will run for a long long time - maybe not as long as a milky candle - but it will drain those batteries right down.

george.
 
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