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What's the best way to add a battery like device to a dynamo light (self.askelectronics)

submitted 3 months ago by coke38 to c/[email protected]

15 comments fedilink hide all child comments

Hello everyone, I bought a bottle dynamo for my bicycle with a rear and front light. Though I have one little tweak that I would like to add and that's a way to keep it light up for about 1 minute (at least 30 sec) without pedaling. I thought of putting a capacitor in the circuit to store some energy but I would like what do you all think of it ?

Thank you for your time and have a nice day you all !

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[–] tia 1 points 2 months ago (3 children)

I've actually done that with a simple single diode rectifier and a supercap with zener voltage limitation:

If your supercap has a too low series resistance for the LED to light immediately you need an additional resistor in series with it. It is simple and small enough to directly fit inside the original lamp casing and has been working without a problem for over 3 years.

[–] coke38 1 points 2 months ago* (last edited 2 months ago) (1 children)

What I wanted to do was something like that IMG_20240925_092655

Though you seem to have a better knowledge and better circuit. I bought 2 super cap 5.5v so I wanted to put them in series (though get half the capacitance). Your approach seems to be better and I may take it. Though mine should be working ? Keep in mind that I'm a nooby in electronics and I keep learning from the internet so not the best to have solid base...

Does your solution works with 5.5V, the 6V dynamo does not blow it ?

Thank you for your answer I really like it.

[–] tia 1 points 2 months ago (1 children)

Your solution may very well also work, good thinking. A few things to consider though:

Putting capacitors in series requires balancing them
A silicon full bridge rectifier drops ~1.4V frm the input
Incandecent bulbs require a lot of current to get going, this may result in a delay for them to turn on

[–] coke38 1 points 2 months ago

Ok, I forgot the voltage drop =\ I got LED light so should be fine. What I should do is put your circuit to the test without the capacitor and check if the voltage is low enough for the capacitor to handle ? How should I balance the capacitors ? (Even if I will not take this path, I would like to know)

Thanks again for your help

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