C
chris
Guest
I bought a shake light that uses a LED for light output.
When I opened it up, I noticed it has 2 Lithium 3v watch batteries in
addition to the capacitor which I thought was what stored the power
from the shaking.
Well, I removed the two batteries to see how the light would perform
just on the capacitor along and it was about half the light output.
So I shook and shook but it wouldn't change. If I had the light on
while shaking it was as bright as with the batteries but only briefly.
So, my question: what is it about the circuit that makes the
capicitor not enough to properly power the LED?
It's a very simple design - the cap has a resistor leading to the LED
on one side and a direct connection on the other. The batteries poles
are in paralell with the cap. diodes convert the AC shake to DC and
dump into the cap and batteries directly.
It's a 5.5v cap but I can't read the uF.
I measure the voltage on the cap and it reads 5.2 under no load. when
the light is on it reads about 2.8. And I since I just removed the
batteries I'm assuming that the cap is fully charged. I've also tried
changing the resitor but it didn't make much of a difference (3ohms to
65ohms all seemed to have the same result.)
When I opened it up, I noticed it has 2 Lithium 3v watch batteries in
addition to the capacitor which I thought was what stored the power
from the shaking.
Well, I removed the two batteries to see how the light would perform
just on the capacitor along and it was about half the light output.
So I shook and shook but it wouldn't change. If I had the light on
while shaking it was as bright as with the batteries but only briefly.
So, my question: what is it about the circuit that makes the
capicitor not enough to properly power the LED?
It's a very simple design - the cap has a resistor leading to the LED
on one side and a direct connection on the other. The batteries poles
are in paralell with the cap. diodes convert the AC shake to DC and
dump into the cap and batteries directly.
It's a 5.5v cap but I can't read the uF.
I measure the voltage on the cap and it reads 5.2 under no load. when
the light is on it reads about 2.8. And I since I just removed the
batteries I'm assuming that the cap is fully charged. I've also tried
changing the resitor but it didn't make much of a difference (3ohms to
65ohms all seemed to have the same result.)