led + supercap + dynamo vintage headlight

keys · Apr 7, 2013

Hi all,

This is my first post, though I've been reading as a guest here occasionally. I just finished my DIY headlight yesterday and thought I'd share it with you. It is not as advanced as some stuff I see here but kind of proud anyway.

Pics here: https://www.dropbox.com/sh/jalb5yprn57k7j1/RtSAnCwlDt

I have used a 1W cold white LED, a diy diode bridge, one resistor and two 2.7 V 25 F supercaps (that is not a typo) in series. I've also added a switch to prevent the light from staying on when parked in public. The whole thing is currently powered by a bottle dynamo which performs pretty good: 5 minutes of cycling is good for 20~30 minutes of useable light. Guess that 1W was an overestimation. I will be replacing this by a diy magnic-light-ish dynamo but my last prototype exploded so this needs some work

.

p.s. i'm a theoretical physicist so bear with me on the soldering :huh:.

--edit-- Material cost: about 20 euro ($25)

BobRoss · Apr 7, 2013

Neat! I love how those old lights look. You should be rightfully proud.

How did your last prototype explode? It seems like the 2.7V rating on the series caps could make that part susceptible to little explosions. My first try at upgrading a dynamo resulted in a lot of fried LEDs from hooking them up to charged capacitors - that lesson just didn't seem to stick.

Also, since you are theoretical physicist, shouldn't you be harnessing something like weak atomic forces or cosmic rays to generate light? Magnets and coils must seem pretty pedestrian.

keys · Apr 8, 2013

Well I got tired of black holes so figured I'd shed some light and settle for a little more mundanity

.

The exploded prototype was not hooked up to the light itself, it was just a dynamo. I tried to create a dynamo based on the magnic light patent. I had my design 3D printed but some part turned out to be too large. In an attempt to fix this I put the part onto a Dremel which unraveled the very fabric of the space-time continuum almost destroying the entire universe had I not unp well it just shattered.

I need to find the time to redesign the whole thing but it'll take a while.

SemiMan · Apr 8, 2013

keys said:
Hi all,

This is my first post, though I've been reading as a guest here occasionally. I just finished my DIY headlight yesterday and thought I'd share it with you. It is not as advanced as some stuff I see here but kind of proud anyway.

Pics here: https://www.dropbox.com/sh/jalb5yprn57k7j1/RtSAnCwlDt

I have used a 1W cold white LED, a diy diode bridge, one resistor and two 2.7 V 25 F supercaps (that is not a typo) in series. I've also added a switch to prevent the light from staying on when parked in public. The whole thing is currently powered by a bottle dynamo which performs pretty good: 5 minutes of cycling is good for 20~30 minutes of useable light. Guess that 1W was an overestimation. I will be replacing this by a diy magnic-light-ish dynamo but my last prototype exploded so this needs some work .

p.s. i'm a theoretical physicist so bear with me on the soldering :huh:.

--edit-- Material cost: about 20 euro ($25)

Those supercaps really do not like higher voltages than they are rated for. You may want to add a zener diode (of a good wattage) to shunt any excess voltage.

Well the 1W was likely accurate, it is just the 0.1watt that you are getting at the end of the 20-30 minutes

.... Still, you have up to 350 joules of stored energy, and even with a 3V cutoff, over 250 joules. With an efficient circuit you could get over 4 minutes at full brightness.

BobRoss · Apr 8, 2013

keys said:
Well I got tired of black holes so figured I'd shed some light and settle for a little more mundanity .

The exploded prototype was not hooked up to the light itself, it was just a dynamo. I tried to create a dynamo based on the magnic light patent. I had my design 3D printed but some part turned out to be too large. In an attempt to fix this I put the part onto a Dremel which unraveled the very fabric of the space-time continuum almost destroying the entire universe had I not unp well it just shattered.

I need to find the time to redesign the whole thing but it'll take a while.

Ha! Thanks for sparing space-time.

Thanks for linking that patent - I can't wait until 3-D printers are affordable enough for me to justify the purchase. Also, I need a garage.

Speaking of super-caps, I think minisystem has designed a circuit that used a super-cap with a boost circuit to get more juice out of the caps - it's up on CPF somewhere. You may get a brighter stand lamp with something like that - I found it to introduce too much complexity in my recent efforts, but I could see doing it when I've got a little more experience.

SemiMan · Apr 8, 2013

Do you think there would be any interest in an off the shelf supercap board:

- Boost (or buck)
- Adjustable max current
- Auto low when you stop
- etc?

Semiman

keys · Apr 8, 2013

Actually I don't own a 3D printer, I use Shapeways. It's kind of expensive, but way cheaper than buying your own printer.

I'll look into the boost circuit en especially the zener diode shunt. But 350 joules is too much, right? E=1/2*C*U^2 per capacitor. Should equal max. 182 joules for two caps.

SemiMan said:
Do you think there would be any interest in an off the shelf supercap board:

- Boost (or buck)
- Adjustable max current
- Auto low when you stop
- etc?

Semiman

A sort of controllable supercap power supply? Maybe. I would just use the circuit and create my own board but there might be a market. Perhaps in combination with an Arduino-controller? I'm not an expert in electronics though, can't really judge how much effort it saves.

SemiMan · Apr 8, 2013

keys said:
Actually I don't own a 3D printer, I use Shapeways. It's kind of expensive, but way cheaper than buying your own printer.

I'll look into the boost circuit en especially the zener diode shunt. But 350 joules is too much, right? E=1/2*C*U^2 per capacitor. Should equal max. 182 joules for two caps.

A sort of controllable supercap power supply? Maybe. I would just use the circuit and create my own board but there might be a market. Perhaps in combination with an Arduino-controller? I'm not an expert in electronics though, can't really judge how much effort it saves.

If I was making the board to sell, I am not likely to give away the schematic

.. though it would likely cost more for someone to do their own board than buying one.

Size would be the order of the day, so no Arduino though it may have a controller on it.

Yes made a mistake in my calcs ... 182 joules max (assumed 5.4 volts) , with 126 for a 3V cutoff. That does sound more realistic, but not nearly as exciting!

Semiman

jdp298 · Apr 8, 2013

Hi Ho

Love the use of an old dynamo headlight. If you need to see your way around dark places, I can recommend getting 2 together and a focusing lens of not more than 10 degrees for the LED. 6000 miles with this setup and still not dead in London, so it's probably working alright.

Can thoroughly recommend a hub dynamo if you've got the time to build your own front wheel.

And I want capacitors, can you get me a couple or 4?

Savvas · Apr 9, 2013

I'm trying to work out how you have the caps and resistor arranged. I can see you have the 2 caps in series. Do you just have them across the led in series with the resistor?
ta,
Savvas

keys · Apr 9, 2013

@Savvas Yup, I've added a circuit drawing to the folder shared in the op.

@jdp298 Thought about that, but I first want to try the touchless magnic dynamo. And I can send you as many as you like, my fee is only 10% ex shipping

. Or you could drink from the same well as me @ conrad, farnell, mouser, rs-electronics.

@Semiman I revise. Think it might be quite useful after all. Do you mean something like a split-pi or Cuk based board?

SemiMan · Apr 10, 2013

keys said:
@Savvas Yup, I've added a circuit drawing to the folder shared in the op.

@jdp298 Thought about that, but I first want to try the touchless magnic dynamo. And I can send you as many as you like, my fee is only 10% ex shipping . Or you could drink from the same well as me @ conrad, farnell, mouser, rs-electronics.

@Semiman I revise. Think it might be quite useful after all. Do you mean something like a split-pi or Cuk based board?

Keys, I would probably either go straight boost for maximum efficiency and/or SEPIC as there are nice chips out there for doing this at high efficiencies and low voltages. My goal would not be to make the cheapest thing on the planet (those supercaps are not cheap anyway), but to make something interesting for the enthusiasts, with features on both the output side and charging side. Whatever circuit I made would likely be universal (with s/w) for supercaps, NiMh and LiFePO4.

I do work in solar lighting and think I can repurpose some tech (not obviously) for this.

Semiman

ianfield · Apr 19, 2013

keys said:
Well I got tired of black holes so figured I'd shed some light and settle for a little more mundanity .

The exploded prototype was not hooked up to the light itself, it was just a dynamo. I tried to create a dynamo based on the magnic light patent. I had my design 3D printed but some part turned out to be too large. In an attempt to fix this I put the part onto a Dremel which unraveled the very fabric of the space-time continuum almost destroying the entire universe had I not unp well it just shattered.

I need to find the time to redesign the whole thing but it'll take a while.

If you could invent a black hole inverter; it would emit infinite light and have zero mass.

Savvas · Apr 25, 2013

Hi Keys,

what's the reflector that you've used there please and where does it come from?

thanks,

Savvas

keys · Apr 26, 2013

The light was already on the bike, I bought it second hand so I can't help you there, sorry. It's not really impressive though, it has a 110 degree angle or something

led + supercap + dynamo vintage headlight

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