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LED Flash light ..Pulsed LED, underdamped oscillations

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audioguru said:
That's not what I meant either.
My wifey gets mad at me because my blinking LEDs are blinding her. I have them all over the place! :lol: :lol:

Try using beepers instead. With a bit of careful design, you can make them sound like crickets. Put nature right into your living room. :lol:
 
Hey Willie,
The Putfiles play! I heard your shaker in the background going like crazy and saw the motors turning rather slowly. Do you have enough power to drive an LED brightly?
 
i think so ..
i found this relationship on a ultra capacitor site. maxwell i think..
t=CV/I , a dirivation of Q=CV..
@ I = 10 mA and 2.2 F worth super caps.. and 5.5 V
should give 20.16 min. of light
and 4.3 sec of charging @ 300mA..
the white led is pretty bright at 10 mA..
 
If you use a constant current circuit (that needs extra voltage) for the LED, after 10 minutes the cap's voltage will be down to 2.75V, won't it?
The LED might be powered for only 5 minutes.

I think your generator's current was measured shorted, with no output voltage. I think the current will drop exponentially as the cap's voltage rises during its charging, causing the charging time to be much longer.
 
how about if i put a rechargeable battery below the caps..

I think your generator's current was measured shorted, with no output voltage.
not really , if you recall i was using a crappy ammeter , and was getting about 3V Peak with it connected directly to the diode bridge output..
 
it was one volt ,a little over ..see page 2..
so yeah, it will take longer than 4 seconds.
my goal was 30 seconds..of shaking for 20 min. of light..
 
actually let me check .. that pic on page 2 was an older one it only had ten peaks , i'm getting fourteen now , page six..
EDIT:: ok i was right the first time it is 2.75 V Peak @ over 250mA..
 
The cap will charge with average current, not peak. You will be shaking until your arm falls off! :lol: :lol:

What's the 10mA light for, a book-light? Can you read while you are shaking the generator? :?:
 
*sigh* , what are you talking about ?
i thought we have been all through this?


at present i am getting over 250 mA average current @ 2.75 V same as the pic on page 6 ( just smaller)
 
The max voltage for the super-caps is 5.5V but your shaker puts out 15V.
How are you going to limit it?

TI used to have a low drop-out current source IC but I couldn't find it. What are you going to use to regulate the LED's current as the cap's voltage falls when it is discharging?
 
audioguru said:
The max voltage for the super-caps is 5.5V but your shaker puts out 15V.
How are you going to limit it?
i'll cross that bridge when i get to it..
probably tommorrow or the next day the super caps will arrive..
TI used to have a low drop-out current source IC but I couldn't find it. What are you going to use to regulate the LED's current as the cap's voltage falls when it is discharging?
i was thinking of a PIC driving a constant current source with PWM ..
 
Why do Americans wait so long for delivery?
I'm in Canada and I can order something from an American distributor like Digikey or Newarkinone tonight, and it will be delivered tomorrow morning, even after it goes through customs.

When you overvoltage the super-caps, I wonder if they will just short, or go "POP". Did you order extras?
 
Oh goody! All 10 super-caps won't be exactly the same, so will overvoltage sequentially, like a string of firecrackers. Please post the video. :lol: :lol:
 
I finally connected all ten .22F caps together , in parallel, for a total capacitance of 2.2 F.. :shock:
G1 is two NiMH batteries at 2.26V :: NOT enough to light the led , by itself..
R is 280 ohms
after charging them up to 5.5 V and after turning on the switch , the initial current was 15 mA..
After 19 min. current was 4.5 mA
After 20 min. current was 4.2 mA.. still plenty bright..
that is with out blinking , at all..
it took 3min 22 sec to charge them up to 5.5 V
 

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