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 !
I could be wrong, but wouldn’t the capacitor keep it from turning on until charged?
Yes but it should not be like 30 seconde long I think, so it should be OK for a bicycle :)
It should be possible to wire it so that when the battery is on, the light turns on instantly while also charging the capacitor. Battery meaning paddling
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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 ?
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Indeed, 2 pair of 2 wires so 4 wires can be connected to the dynamo.
I will try that, I need to find some proper diode then find the capacitor or buy it and I should be good. I’ll keep you in touch if I manage to find the parts. Thank you
Excuse me if I’m wrong but the description of your front light says in the first sentence: "The AXA Nxt 60 is a dynamo front light […] with a Steady light function allowing you to have 4 minutes of light when standing still. " Is that not already what you want?
Really good point, though as a stupid human I didn’t understood what was the difference between the Nxt 60 steady and the Nxt 60 E bike… Now I know. I don’t have this marvelous option =\ explaining why the back doesn’t light up either… Thank you for pointing it out, I couldn’t get the article from the site itself so I took another seller and it was not available (it is now)
Your typical bike dynamo puts out 6V AC. I bet yours does as well, so that diode sounds like a good idea.
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
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.
What I wanted to do was something like that
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.
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
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
