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Is there a way to smooth out/reduce low-speed flicker?

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Is there a way to smooth out/reduce low-speed flicker?

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Old 04-12-18, 06:21 AM
  #26  
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Originally Posted by CliffordK View Post
It should be easy enough to build a box with a bridge rectifier and capacitor to reduce ripple to be placed between the generator and the headlamp.

The headlamp shouldn't care whether it is AC or DC power feeding it. Is the bulb incandescent or LED? If it is incandescent, then replace with a LED bulb at the same time.

Once one has DC, then it should be possible to add a backup battery, although the "super capacitor" might be a more durable option.
I've made a standlight using that sort of method in the past. The simplicity is certainly appealing, but in the end, I wasn't happy with the results.

One of the limitations is that it didn't reduce the power draw of the headlight when the battery was supplying power. In a system where the light is using most of the power that the dynamo can generate, it's very difficult to divert energy to charging the battery.

There is also the need to have some sort of regulation for the charging and discharging modes. I was using a battery made of 5 nicad AA cells, and it did charge reasonably quickly when the light was off. Without a charge regulator, though, the high level of trickle charging shortened the battery's life.
Similarly, a discharge regulator is needed to avoid over-discharge. With 5 cells in series, there is the additional problem of the cells becoming unbalanced, meaning that one cell discharges before the others and becomes damaged as the other cells continue to source current to the load through the discharged cell.

Those are my experiences. I do encourage others to experiment and see what they can come up with, though.


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Old 04-12-18, 08:14 AM
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Originally Posted by KD5NRH View Post
Translation: "DON'T YOU TELL ME NO SCIENCE!!! MAH FEELZ TELL ME THEY GOOD!!!"
No objection to the science, you just haven't explained why you referred to my lighting setup as a "greenie toy" or why you're being needlessly argumentative.
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Old 04-12-18, 09:59 AM
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Many lithium battery packs have built-in charge regulators. Of course, that is also the reason some bicycle lights have the annoying tendency to blink out with a low battery.

What is the power output of the bicycle dynamo? A lithium battery should have a power range of about 3.6v to 4.2, or two of them in series, 7.2v to 8.4v, I think.

If the LED is capable of lighting at about 4V, then one could potentially add the Lithium battery in the circuit with a simple charging cut-off.

NiMH batteries, of course have a voltage of around 1.25V, and thus using 5 of them in series to attain about 6V. Unfortunately I'm not seeing 5-cell NiMH controllers as independent units, but they have to be out there somewhere.
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Old 04-12-18, 11:33 AM
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the luxos u has a battery that should reduce flicker. Bad news is, that light has the worst flicker of any I have used on a long climb. My guess is one of the newer small lights that they sell would be better

you probably could add a battery to a dyno light. However, if you ever look at the circuitry in a good dyno light, you will immediately give up on the idea
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Old 04-13-18, 09:10 AM
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Originally Posted by CliffordK View Post
Many lithium battery packs have built-in charge regulators. Of course, that is also the reason some bicycle lights have the annoying tendency to blink out with a low battery.

What is the power output of the bicycle dynamo? A lithium battery should have a power range of about 3.6v to 4.2, or two of them in series, 7.2v to 8.4v, I think.

If the LED is capable of lighting at about 4V, then one could potentially add the Lithium battery in the circuit with a simple charging cut-off.

NiMH batteries, of course have a voltage of around 1.25V, and thus using 5 of them in series to attain about 6V. Unfortunately I'm not seeing 5-cell NiMH controllers as independent units, but they have to be out there somewhere.
Regarding dynamos and their output power and voltage.... they are interesting items! They are designed to have a short-circuit current of roughly 0.5A. The traditional bulb for dynamo lights was 12 ohms, which was pretty close to a short circuit for the dynamo. As a result, the system operated at a consistent 0.5A over most of the speed range. Pretty nice for a very simple system, and a testimony to the cleverness of the dynamo designers.

Without a standard 12 ohm load for the dynamo, the voltage and power can vary quite a bit over speed. With a negligible load, I've measured 100V on a hill that was part of my routine commute. Granted, it's a 14% grade and I was going 50mph, but it does show that the dynamo can generate quite a bit of voltage. If you always have your lights on, then that will load the dynamo and keep the voltage down. In my case, I had the light (an incandescent Lumotec) off and was just charging the battery. If the battery is fully charged, then it's not loading the dynamo and the circuit will see the 100V. If the battery charge controller isn't specifically designed to handle these voltages (and it is expensive to do so), then the controller could be destroyed, which might result in the destruction of the battery and light.

At more routine speeds, the voltages are lower. I've measured 22.8VAC out of my SON at 16mph with just a 1000 ohm load.

Changing subjects slightly... my guess is that LED lights with a single LED will tolerate being driven by a battery with a voltage somewhere in the 4.5V to 7V range. I've opened up a B&M Eyc, and it appears to use a buck converter to convert the 6V, 0.5A power into 3 watts at 3V, 1A. Buck converters shouldn't have trouble with the low impedance of a battery.

On the other hand, I've repaired a Supernova Triple that was connected to an e-bike's battery, and the light was not designed to be driven by such a low impedance power source. The design was very efficient.... it just rectifies the power and drives the three LEDs in series. It relies on the dynamo to limit the current to 0.5A. Unfortunately, the battery must have supplied many amps into the light, because it blew out one LED, a handful of other semiconductors, and even fused one of the circuit board traces.


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Old 04-13-18, 09:52 AM
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Thanks for the explanation and voltages. It looks like you've done some detailed research on the issues.

Originally Posted by steelbikeguy View Post
On the other hand, I've repaired a Supernova Triple that was connected to an e-bike's battery, and the light was not designed to be driven by such a low impedance power source. The design was very efficient.... it just rectifies the power and drives the three LEDs in series. It relies on the dynamo to limit the current to 0.5A. Unfortunately, the battery must have supplied many amps into the light, because it blew out one LED, a handful of other semiconductors, and even fused one of the circuit board traces.

Steve in Peoria
I thought typically the amps were determined by the circuit.

(V=IR), (I=V/R), (P=IV)
V = Volts
I = Amps
R = Resistance
P = Power

So, for the most part, one can drive any 12V appliance with a car battery that may be able to crank out as much as 1000A at 12V.

However, it may not be as straight forward if the voltage varies significantly.

It sounds like a bicycle dynamo has some of the same issues as home generated solar/wind power. Solar power for the most part is limited by the maximum energy of the sun. But, wind power and voltage can vary considerably based on how much wind.

I have a SON hub that needs to be built into something. Perhaps it is time. Then I suppose I could try making a light to go with it.

It sounds like there are definite advantages of the vintage incandescent light bulbs, but there should be more modern circuits possible too.
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Old 04-13-18, 10:29 AM
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Add a 2nd, Battery, headlight.

if your dynamo headlight has a standlight capacitor, it gets charged after riding fast enough , for a little while..

A smaller wheel rotates faster at the same speed as a bigger one, like 16" vs 26" ...

[Idk what headlight you use, my B&M Eyc senso T flickers, again as i slow to walking speed,
because its stand light switching uses different lower level output LEDs. they're the day running lights

The eDelux Schmidt does not, it stays on until the capacitor discharges..]

Back to OP:


Originally Posted by agmetal View Post
Out of curiosity, what makes it different from this setup from the 1940s and '50s?

Sturmey-Archer Heritage :: History
Sturmey-Archer Heritage :: History
Of Course it matters, no LED lights were made back then, they used bulbs... 3w divided up 2.4w front, 0.6w rear


Sturmey-archer-sun-race .. hubs are made now, in TW. and as others now do, put out AC..




..

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Old 04-13-18, 11:11 AM
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Originally Posted by CliffordK View Post
...
I thought typically the amps were determined by the circuit.

(V=IR), (I=V/R), (P=IV)
V = Volts
I = Amps
R = Resistance
P = Power
that is true, but the power source is part of the circuit too. The dynamo has resistance and inductance, and the open-circuit voltage varies linearly with speed.
By the same token, even a battery has internal resistance, inductance, and capacitance. Due to the electro-chemical nature of a battery, it's even harder to model than a dynamo. Generally speaking, for the batteries that most folks are familiar with, the source resistance is quite small; much smaller than that of a bike dynamo.


Originally Posted by CliffordK View Post
I have a SON hub that needs to be built into something. Perhaps it is time. Then I suppose I could try making a light to go with it.

It sounds like there are definite advantages of the vintage incandescent light bulbs, but there should be more modern circuits possible too.
The biggest advantage of an incandescent bulb over LED is that incandescent bulbs don't need/want heatsinking.
Making a tolerable LED headlight is pretty easy, at least as far as the electrical aspects are concerned. A bridge rectifier, a filter capacitor (if so inclined), and two white LEDs wired in series.
Making the light waterproof and vibration-tolerant, getting suitable optics and LEDs that will create a beam that you like, providing suitable heatsinking, etc... that's really where the work is.
Incorporating a standlight can be helpful too. There was a good thread on CandlePowerForums on this a number of years ago....
Standlight circuits (Will this circuit work?))

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Old 04-14-18, 05:45 AM
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I used to make my own lights, but the headlights you can buy are so much better it's not even close. haven't given up on making my own tail lights though.
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Old 04-14-18, 10:32 AM
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Originally Posted by unterhausen View Post
I used to make my own lights, but the headlights you can buy are so much better it's not even close. haven't given up on making my own tail lights though.
very true... that's why I found a dead B&M Eyc light... my hopes are to use it as a basis for some electronics tinkering. The Eyc's optical design is much better than anything that can be done with conventional symmetric optics such as would be used in a flashlight. The only downside is that someone might think it looks nice enough to be worth stealing. Never had that problem with my home-made lights!

OTOH, if you have a desire for some special function or feature, that might a reason to cobble together something yourself. (and this brings us back around to the OP's question about no-flicker modifications)


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Old 04-14-18, 11:43 PM
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@CliffordK, it's really not worth making a headlight for a dynamo. The off the shelf stuff can't be beat(en).

And are you really not using a dynamo yet? Get on it, man!
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Old 04-15-18, 01:36 PM
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Originally Posted by agmetal View Post
I have one particular ride in mind for this as a potential problem, Boston's "Midnight Marathon" ride this upcoming weekend. Maybe I'll take my USB rechargeable light with me as a backup.
Still doing the ride?

(I think lighting is going to be the least of your worries.)
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Old 04-15-18, 01:56 PM
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Originally Posted by athrowawaynic View Post
Still doing the ride?

(I think lighting is going to be the least of your worries.)
Unless the weather makes a dramatic turn in the next few hours, probably not. My vision isn't great at night, and even with good lighting, it's difficult to see details in the road (potholes, etc.) when things are wet. On top of that, I don't have suitable rain gear for that long of a cold & wet ride, the bike I'd ride has rim brakes and a new chain, and it just generally sounds miserable.

I'm really disappointed - I was really looking forward to this ride! The last few years it's been fun, but tonight just sounds miserable
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Old 04-16-18, 08:22 AM
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Originally Posted by KD5NRH View Post
Translation: "DON'T YOU TELL ME NO SCIENCE!!! MAH FEELZ TELL ME THEY GOOD!!!"
You appear to be saying it's not adequate for him, though I don't know why you would say that. What are you really saying?
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Old 04-16-18, 10:39 PM
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Originally Posted by noglider View Post
You appear to be saying it's not adequate for him, though I don't know why you would say that. What are you really saying?
Well, I suppose if he's sufficiently dim himself, then even a sputtering candle could be seen as a searing light by comparison. OTOH, some of us prefer to see the road clearly well in front of the bike, without perceptible flicker, regardless of speed.
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Old 04-17-18, 07:02 AM
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Originally Posted by KD5NRH View Post
Well, I suppose if he's sufficiently dim himself, then even a sputtering candle could be seen as a searing light by comparison. OTOH, some of us prefer to see the road clearly well in front of the bike, without perceptible flicker, regardless of speed.
So "good enough for me" is invalid because you disagree. And he's defective for finding it sufficient. OK, good to know. But maybe you should consider that other people's viewpoints have reasons. Sheesh.
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Old 04-17-18, 08:33 AM
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Old 04-20-18, 04:59 PM
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Originally Posted by noglider View Post
@CliffordK, it's really not worth making a headlight for a dynamo. The off the shelf stuff can't be beat(en).

And are you really not using a dynamo yet? Get on it, man!
It still might be worth seeing what makes it tick.

I suppose those bottle generators really turned, me off from the whole generator concept...

Recently I've been commuting on 3 or 4 different bikes, so lights I can move around work well for me. But, I'll probably choose one bike as a primary commuter, and then work around that one, with battery lights for the other bikes.

I'm not quite sure how to attach the dynamo to my toe lights.

The other thing is that I'm thinking about my next rough country touring build. Thus having a portable recharging station would be a big benefit.

I was browsing today, and this popped up:
https://www.ebay.com/itm/Voltage-Reg...r/152857690060
or as a hub + regulator package:
https://www.ebay.com/itm/DH-S500-Qui...r/152632658707

Assuming it does what it is supposed to, it should give a decent regulated 5V USB power source which then could be used to power phones, battery chargers, etc.
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Old 04-20-18, 05:43 PM
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Originally Posted by CliffordK View Post
.....

I was browsing today, and this popped up:
https://www.ebay.com/itm/Voltage-Reg...r/152857690060
or as a hub + regulator package:
https://www.ebay.com/itm/DH-S500-Qui...r/152632658707

Assuming it does what it is supposed to, it should give a decent regulated 5V USB power source which then could be used to power phones, battery chargers, etc.
As someone who spent a career designing electronics that had to be reliable, I get really queasy when I look at some of the cheap electronics coming out of China (such as this). That regulator is the only thing keeping the dynamo's high voltages from getting to your phone or other device and causing potentially severe damage. Considering the cost of most phones nowadays, it's worth thinking about the value of buying the cheapest electronics in the world.

The issue of USB chargers that are powered by dynamos gets discussed a lot. A quick search should pull up a handful of these threads.

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Old 04-20-18, 05:59 PM
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Originally Posted by steelbikeguy View Post
As someone who spent a career designing electronics that had to be reliable, I get really queasy when I look at some of the cheap electronics coming out of China (such as this). That regulator is the only thing keeping the dynamo's high voltages from getting to your phone or other device and causing potentially severe damage. Considering the cost of most phones nowadays, it's worth thinking about the value of buying the cheapest electronics in the world.
It should be easy enough to build a USB to multifunction tool (volt meter) interface that would be stable enough to take out on the road before hooking up one's phone.

Of course, that doesn't mean one wouldn't get 300+ miles from home and have internal circuits fry in the device and power surges coming out of it. Adding 4 NiMH cells should give one a bit of a power sink at around 5V.

I've got one 8.4V Lithium Ion pack with a USB out port, which I think dumps 8.4V out to one's device
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Old 04-20-18, 06:15 PM
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Originally Posted by CliffordK View Post
It should be easy enough to build a USB to multifunction tool (volt meter) interface that would be stable enough to take out on the road before hooking up one's phone.

Of course, that doesn't mean one wouldn't get 300+ miles from home and have internal circuits fry in the device and power surges coming out of it. Adding 4 NiMH cells should give one a bit of a power sink at around 5V.
I'm thinking mostly about the quality of the materials and the workmanship. It might be like the cheap digital scale that I bought that simply didn't work when it arrived (which did make for some fun when I tore it all apart to see what was inside). The workmanship was truly awful.

More likely, something made so cheaply will work for 20 hours.. or perhaps 2 hours, if you use it while riding on a rough road. If the wrong solder joint fails, it's easy to imagine that it could cease to regulate the voltage and deliver a considerable voltage to your phone or gps device.

A shunt regulator, such as a 3 watt power zener diode, would clamp the voltage pretty well. Of course, then you've turned it into a bit of an electronics project, and you've got to worry about your own workmanship!

There are various other aspects to consider if you want to build a regulator yourself. I seem to recall discussing them once or twice on BikeForums. If not, it's probably been discussed on CandlePowerForums, and certainly on BikeCurrent (although that might have been 20 years ago). If nothing pops up, we can probably start a new thread on the subject, if there is interest.

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Old 04-21-18, 05:24 AM
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I would really like to see a schematic for one of the better headlights. I have popped a couple of them open and shut them quickly again before something crawled out. I had a supernova that failed so I looked inside, you'd think that with all those electronics they could make it work better
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Old 04-21-18, 07:50 AM
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@CliffordK, read the other threads in this section. The cheap voltage regulators have not worked well, if at all. A good one is over $100. They're really only useful if you're going to be away from a power outlet for days. Other than that, it's better to carry a battery or two. That's what I do. I connect my phone to a battery on the bike. I power (two of) my lights with the dynamo.
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Old 04-22-18, 12:04 PM
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Originally Posted by unterhausen View Post
I would really like to see a schematic for one of the better headlights. I have popped a couple of them open and shut them quickly again before something crawled out. I had a supernova that failed so I looked inside, you'd think that with all those electronics they could make it work better
I repaired a fellow's Supernova Triple a couple of years ago. He had gotten the light for free, as it had been damaged by connecting it up to an E-bike's battery. There was plenty of damage and required a number of new parts. It kept me entertained for weeks.


Schematic:



view of the main circuit board's "top" side. There are some capacitors on the back.



Steve in Peoria
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Old 04-22-18, 09:19 PM
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This has turned out to be a very interesting discussion. I can't see why someone can't build a "Hybrid" dynamo set-up that would incorporate a small Li-ion battery back-up ( for those long slow climbs when you are just poking along ) that would automatically adjust the output of the lamp by bleeding off just enough current from the aux. battery to prevent the dreaded flicker phenomenon. Done right the circuitry could be designed to kick in a minimal current when the dynamo is just not outputting enough current to meet the needed minimum LED current requirement to help eliminate any low output flicker. Even better if this was programmable by the user so he could either set the level at which output the battery would kick in. Now add a feature like momentary remote high beam and now you have something even more useful.

Super capacitors are great but they to need to be charged as well and I doubt they could hold a charge as long as a Li-ion cell. Yes at some point you would have to charge the Li-ions but with the minimal current drain they would likely see they would likely only need to be charged ( externally or though a USB cable ) only a couple times a year ( depending of course on how many long slow hills at night you ride on a regular basis and how bright you set the current by-pass for.. ). Judging from the size of some of the dynamo lamps I've seen online they could likely make one with enough extra room to house a couple parallel configured 14500 Li-ion cells ( 1500mAh total ) or a similar single cell Li-po cell ( 1700mAh ). The Raveman CR-500 lamp I own uses such a battery. On it's lowest steady output mode ( Eco-Mode ) it claims to provide 16.5 hrs of run time @ 50 lumen. When I turn the CR-500 on it's eco-mode I find it provides more than enough light to see if I'm only poking up a long hill at 3-5mph.
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