flashlight with no batteries

[McGuinn]

I think that the trick is that they have used a memory retention cap instead of a standard one.

**broken link removed**

This one has a value of 1 farad and a leakage current of 315uA.

About the schottky diodes, that's a good idea. I see that they go up to 3A, so I may use these in another project...!

 

[plot]

I think that the trick is that they have used a memory retention cap instead of a standard one.

**broken link removed**

This one has a value of 1 farad and a leakage current of 315uA.

About the schottky diodes, that's a good idea. I see that they go up to 3A, so I may use these in another project...!

seems simple enough, would there be enough current to power LEDs for 20 minutes though? Seams like it would take alot.. unless they weren't very bright LEDs.

 

[petesmc]

You were right, 1F, 5.5V capacitor. Heres some pictures from mine...
Any ideas on how you want the LED tested? At 5.5V maybe, to see current draw?

Oh, and the magnet inside is DAMN strong. Don't let your finger get between it and another metal object ready for picking up! If it comes within one foot or slightly more on my monitor, it goes crazy...

-Peter

 

[McGuinn]

Ah!, That's great! We can see the bridge rectifier also.
The next thing is to find out what current the LED is pulling.
With what Nigel provided us, even at 10mA, a 1F cap would only last 100 seconds, so to get it to last 1200 seconds it would need to run at 0.83mA. That's very very little...

Does anybody know whether the torch can last for 20 mins after a 30 second shake?
I wonder whether they are relying on the fact that during use the torch will be moving, causing some recharging of the cap.

Petesmc, run it at 5VDC!

 

[Gandledorf]

It's possible that they're running an ultrabright at very low current, and then using a well designed set of optics to boost the visible beam. What does the optical assembly look like?

(And I bet they're counting on the movement. Remember, manufacturer specs are always absolute best case scenarios.)

 

[petesmc]

I can say though, that it certainly did last at least 10 minutes. Though it was very dull. Even in normal use it wasn't too bright. And i would say, at least 2 minutes of shaking.

It has a mirror behind it to center the light, and the lens was convex to center light i guess.

I tested the LED at 9V (! I should've worn protective goggles...but i was lucky, didn't hit me in the face.)

V = 8.97 V
I = 0.270 A

There was no change in current for about ten seconds, before the LED turned from blue to orange, then all went CrAzY! I love exploding electronic equipment!

So, at 5.5V. That'd be:

I = 0.166 A

That's a lot...but typical of a normal/bright blue LED...

-Peter

EDIT: Forgot to mention, I compared with my other blue LEDs, and it is actually very bright compared to them. So i'm thinking very bright, maybe ultra bright blue LED.

 

[McGuinn]

Oh Dear!
:lol: :lol: :lol: :lol:
The forward voltage for these things is usualu around 2.5v, so 9 was pushing it. Is there a small resistor in the circuit near the LED? Can you get the value off it using a multimeter!?

WITHOUT blowing stuff up this time? :shock:

 

[panic mode]

I am surprised there is nothing else. It should have few more
components to regulate power (pulsing mode or whatever) otherwise
this should not run very long even with superbright LEDs...
Maybe it's embeded in the plastic under the reed switch or even in
the LED.

Anyway, it's fun to see people blowing things up...

 

[petesmc]

I don't know if it was a resistor or not, but it was kinda broken already i think. I tested the resistance, at 1.01 Megaohms. The little thing has 105 written on it. I've taken a picture with all the components removed. AS you see, the little thing, is sorta two things, though the one on the right has no connectors or anything.

There was nothing inside the plastic thingy, and nothing under the capacitor. There is one marking on the PCB called 'LG02' though. I've no idea what thats for.

-Peter

 

[McGuinn]

Yes, it's a very simple circuit.

Bridge rectifier into capacitor, into switch, with a 1M ohm resistor...

 

[Exo]

I don't know if it was a resistor or not, but it was kinda broken already i think. I tested the resistance, at 1.01 Megaohms. The little thing has 105 written on it. I've taken a picture with all the components removed. AS you see, the little thing, is sorta two things, though the one on the right has no connectors or anything.

There was nothing inside the plastic thingy, and nothing under the capacitor. There is one marking on the PCB called 'LG02' though. I've no idea what thats for.

-Peter

The little things are just Surface mount resistors. You read there value the same way you would read a normal resistor. 105 means
1 0 and 5 zeroes
1000000 ohm

 

[nerosrevenge]

Does anyone have any ideas on the coil or the magnet? What guage wire and how many turns, etc.

 

[bogdanfirst]

you need as many turns as possible.
since you have a small current trough it, you don't need very thick wires.
and the magnet....it has to be a permanent one, very strong.

 

[cowboytuna]

building it was harder than i thought it would be or maybe its because im a beginner? anyway it is hard to find a really strong magnet to do the job. *sad*