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Hi Willi,
Figure 4 shows the IC's supply current with only a 15uA load current. You won't see an LED that has only 15uA through it. :cry:
A constant current source is an automatically variable resistor in series with the load. It is used to keep the current constant through an LED as a load that is continuously turned on, when its power supply voltage is changing.
If you are using PWM, it can keep the LED's brightness constant if the supply voltage changes, then you won't need a constant current source that wastes power.
I don't think your shaker makes enough power for an LED flashlight.
Maybe now you are talking about using a low PWM duty-cycle so the average current is low. Low average current in an LED results in dim brightness.
Maybe you are talking about blinking the LED so it uses less power. A blinking LED makes a lousy flashlight.
I made some, they are an ultra-bright LED that blinks with five 100mA pulses about 20ms each in duration, at about 10Hz, with a 1 second pause in beween. Because they blink very brightly, they attract a lot of attention. Because they are off most of the time, their battery lasts a very long time. I can shine one on the ground at night to see where to walk, but the blinking and pauses aren't good for a flashlight.
My ultra-bright chaser projects make pretty good flashlights, when their PWM is turned up to max duty-cycle and their speed is also max so they are spinning like mad. But then they draw lots of current, about the same current as a single LED, and require probably much more power than your shaker can supply.
just one more thing
if when i shake it with a one ohm resistor connected across just the coils ,and the scope says that i am getting around a volt p-p output ...
1/1 = 1A so where is the available current going when i hook it up to the full wave bridge ???
i should get at least 250 mA fron that ?
nevermind i just figured it out..
the scope is giving instantanious values..
BUT the the bursts of current arent close enough together to average out to anywhere near their instantainious values...
If the shaker's resistance is low enough then a filter capacitor charged by the full wave bridge will charge to the peak voltage of the output of the bridge, just like with a mains transformer supply. :lol:
If you shake it really hard, does your shaker generator produce enough power to burn-out the LED?
If not, then use a 10F super-capacitor and let your shaker charge it for a few hours or days. Then when you let it discharge into the LED you will certainly need a current-limiting resistor, and you can watch the LED dim as the super-capacitor discharges. :lol:
To answer your question no it didnt..
i tried it with a superbrite Blue LED connected in the full wave bridge config.
and in the full wave config. listed earlier
i also connected said blue LED directly across the coil output, still works lol
so i suppose 23 ohms is too high..??
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