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deutrino

@deutrino@mstdn.io · 7 months ago

any #electronics tinkerers out there got a standlight circuit for a 3 watt bike dynamo?

I'm about to drag my bike out of storage, currently it has the dynamo and incandescent lights (2.4W front, 0.6W rear).

I have almost no experience and can barely solder, fwiw. #LearnElectronics

deutrino

@deutrino@mstdn.io replied · 7 months ago

many of the designs out there use a supercapacitor but I'm kind of interested in being contrarian and using a NiMH eneloop battery such that it could maintain charge between rides.

Stahlbrandt

@stahlbrandt@infosec.exchange replied · 7 months ago

@deutrino The dynamo only generates a few watts. Maybe 3W when you load it properly (so that you feel its breaking effect against the tire). If your construction would consist of, for example one 18650 Li batteries with a nominal 3.7V= and 2500mAh (3.7 x 2.5 = 9.25 Wh) you would need some three hours biking to charge it, discarding any inefficiencies in your charging circuit and dc regulators. You would probably look at 4h+ to charge it. That battery would then in theory deliver a few hours of light, eg a 3.5W load could work for some 2.5h without you running the dynamo in-between. Your loading/output stage should probably use low power LEDs that you pulse with a long off cycle.

deutrino

@deutrino@mstdn.io replied · 7 months ago

@stahlbrandt I had been thinking of trying to use an AAA or AA size NiMH battery plus an IC boost regulator, but after searching around, it seems like I'd have to custom design a circuit like that since there aren't designs just lying around on the web, and there are a number of considerations such as whether/how I need to switch over to battery power when dynamo power is too low, etc.

Stahlbrandt

@stahlbrandt@infosec.exchange replied · 7 months ago

@deutrino A dirt simple charger allows for parallel load while charging from the dynamo = you have switches for the light and allow the dynamo to always charge once rolling against the wheel. If you have a hub-integrated dynamo, you’ll need a separate switch from it to be able to disconnect it from your charging circuitry. You may need to take care of over-charging case, but for tests that can potentially be ignored. This way you have no ”smart switching” on/off of source since it is not required.

deutrino

@deutrino@mstdn.io replied · 7 months ago

@stahlbrandt yup, it's a hub dynamo!

honestly I have plenty of time to figure this out, since I (currently) barely use the bike, so I do think I'm going to bite off more than I can chew and do things "my way" with a NiMH cell (or two) even if it requires multiple design & test rounds... I'm currently staying in a household with a ton of electronics gear & parts, I think we even have an oscilloscope and such.

deutrino

@deutrino@mstdn.io replied · 7 months ago

@stahlbrandt I thought of switching to LED for the tail light but I think I'd have to replace the entire front lumiere to switch to LED there, because there's no way it can dissipate the heat even if a 2.4W single-chip drop-in replacement bulb could be found which would collimate with the reflector, etc. although... maybe a lower wattage drop-in replacement bulb could be found and thus leave some spare power for running lights or something.

Stahlbrandt

@stahlbrandt@infosec.exchange replied · 7 months ago

@deutrino Yes, drop-in replacement could be interesting to test. Can be an issue with the large voltage range you’ll have from the dynamo, so you’ll likely need your new stabilization circuitry in place to get a LED to work. A reason for skipping dynamo’s all together and instead use rechargeable LED system on the bike. But, I understand you want to experiment with the dynamo.

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