Ask Electronics

3173 readers

2 users here now

For questions about component-level electronic circuits, tools and equipment.

Rules

1: Be nice.

2: Be on-topic (eg: Electronic, not electrical).

3: No commercial stuff, buying, selling or valuations.

4: Be safe.

founded 2 years ago

MODERATORS

[email protected]

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 !

you are viewing a single comment's thread
view the rest of the comments

[–] [email protected] 3 points 3 months ago (7 children)

I think the largest issue you'll run into is figuring out how to wire it. It definitely sounds like a fun project and possibly an opportunity to try out some of the inexpensive super caps that you can get on eBay for like 3 bucks a piece.

The only caveat I can think of is that you might need to find out how much voltage the generator puts out, as you definitely don't want to pump more voltage into them than they are rated for.

To do that I would open the device and hook up a multimeter to the Dynamo and then spin it as hard as I can and figure out what it's peak voltage is and then purchase and or design your super capacitor bank to handle its peak maximum.

You should also check and see if the device has some sort of rectifier, as Dynamo output is typically AC and LED lights are typically DC, so there is likely some sort of rectification. If you do have a rectifier I would measure it after the rectifier.

It may already also have a capacitor in it, in which case you could simply desolder that capacitor and then set up some breakout cables and run those outside of the case into your bank.

[–] coke38 4 points 3 months ago (6 children)

I should have put the stuff I have, so here you are : Dynamo : https://www.axasecurity.com/bike-security/en-gb/products/lights/7/93903195SC/axa-hr-traction-right Rear light : https://www.axasecurity.com/bike-security/en-gb/products/lights/7/93929195SC/axa-juno-e-bike-6-12v-80-mm Front light : https://www.axasecurity.com/bike-security/en-gb/products/lights/7/92520095SB/axa-nxt-60-steady

Indeed it seems like a great project I think the output is DC though I'm not sure. To be honest I tried to put a capacitor (50V) put it seemed to had no effect (maybe to little capacitance or more probably the coil of the motor should have eaten the storage. Is probably should add a diode to the circuit, am I right ?

[–] [email protected] 1 points 3 months ago (1 children)

Your typical bike dynamo puts out 6V AC. I bet yours does as well, so that diode sounds like a good idea.

[–] coke38 1 points 3 months ago

Seems bad so, I have to make a diode bridge rectifier so =\ need to scrap more diode ! Too bad as I wanted to make something small

load more comments (4 replies)