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#31
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Dynamo/LED power conditioning
On Mon, 7 May 2018 08:15:45 +1000, James
wrote: On 07/05/18 03:01, Joerg wrote: Note the three big 470uF capacitor in the schematic. That's the "flicker reduction trick" :-) Problem is, electrolytic capacitors do not live long in harsh climate conditions such as the black light enclosure baking in the glistening Arizona desert sun for hours every week or riding around the Klondike in a harsh winter. For me the only proper way of lighting a bicycle is with a rechargeable battery. Bull**** alert! We all know how reliable rechargeable batteries are, especially in harsh environments, right? OTOH, here is an electrolytic cap from Vishay, that has a "useful life" of 1,000,000 hours at 40C, and 8000 hours at 125C. https://www.vishay.com/docs/28334/118aht.pdf (The useful life approximately halves for every 10C increase.) If the temperature inside the electronics enclosure was much more than 80C for most of the time the light is in operation (E.g. while you're riding and the light has forced air cooling), the engineer ought to be shot, and that still gives a useful life of over 62500 hours. Or perhaps 1,000,000 Km. Or nearly 25 laps around the Earth :-) -- Cheers, John B. |
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#32
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Dynamo/LED power conditioning
On 07/05/18 13:00, John B. wrote:
On Mon, 7 May 2018 08:15:45 +1000, James wrote: On 07/05/18 03:01, Joerg wrote: Note the three big 470uF capacitor in the schematic. That's the "flicker reduction trick" :-) Problem is, electrolytic capacitors do not live long in harsh climate conditions such as the black light enclosure baking in the glistening Arizona desert sun for hours every week or riding around the Klondike in a harsh winter. For me the only proper way of lighting a bicycle is with a rechargeable battery. Bull**** alert! We all know how reliable rechargeable batteries are, especially in harsh environments, right? OTOH, here is an electrolytic cap from Vishay, that has a "useful life" of 1,000,000 hours at 40C, and 8000 hours at 125C. https://www.vishay.com/docs/28334/118aht.pdf (The useful life approximately halves for every 10C increase.) If the temperature inside the electronics enclosure was much more than 80C for most of the time the light is in operation (E.g. while you're riding and the light has forced air cooling), the engineer ought to be shot, and that still gives a useful life of over 62500 hours. Or perhaps 1,000,000 Km. Or nearly 25 laps around the Earth :-) Oh, c'mon. Surely you're just not factoring in the baking, glistening Arizona desert sun for hours every day... ;-) I learned recently that the sun is 3.4% closer to the earth during the southern hemisphere summer than during the northern hemisphere summer. We also typically have lower pollution levels, and hence considerably more solar radiation to contend with. https://theconversation.com/why-does...one-hole-91850 -- JS |
#33
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Dynamo/LED power conditioning
Joerg wrote:
Why should bicycle lighting be inferior to car lighting? Does anybody make a bicycle dynamo that produces more than 3 watts at 10 mph? bob prohaska |
#34
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Dynamo/LED power conditioning
On 5/6/2018 11:46 PM, bob prohaska wrote:
Joerg wrote: Why should bicycle lighting be inferior to car lighting? Does anybody make a bicycle dynamo that produces more than 3 watts at 10 mph? The power produced by many (most?) dynamos depends on the load, in a counterintuitive way. Most dynamos are approximately constant current (about 0.5 Amp) sources, in the same way that batteries are approximately constant voltage sources. So if you present more resistance to the dynamo, its output voltage will rise so as to pump that same 0.5 Amp through the higher resistance. The result is more power. Putting two lamps in series does this. I did this for quite a while as an experiment back in the halogen lamp days. With my Soubitez roller dyno of the day, I needed something like 14 mph to get both lights brightly lit, so I suppose that was putting out about six Watts. (A bottle dyno would slip doing that.) I wouldn't bother with it today, though. What you need for night riding is not a certain number of Watts, nor a certain number of lumens. You need sufficient illumination of the road. The better B&M lamps certainly give that, in spades. Those are so good there's no need to play around with two lamps or other homebrew tricks, IMO. -- - Frank Krygowski |
#35
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Dynamo/LED power conditioning
On Sun, 6 May 2018 21:54:13 -0400,
Frank Krygowski wrote: On 5/6/2018 3:19 PM, AMuzi wrote: I think Joerg meant that the automobile current from a 12~14VAC alternator source gets run through a diode bride and then (as switched by the regulator) through a lead-acid pile. It's a lot of hardware for a bicycle I agree, but Joerg's seems to work for Joerg's values of performance and efficiency. Frank & I prefer a simple 6VAC tire drive dynamo... For the record, I also have a couple hub dynamos. And two of my formerly "tire drive" dynos are now rim drive. But yes, I certainly prefer those to fussing with recharging or replacing or remembering batteries. Someone noted elsethread the great variation in user requirements, and the choice between dynamos and rechargeables is certainly affected by them. I need a light only infrequently, so for me a dynamo would largely be wasted weight and clutter on the bike. On the other hand, if I rode in the dark often, I could easily see the conclusion tipping the other way. -- Ted Heise West Lafayette, IN, USA |
#36
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Dynamo/LED power conditioning
Theodore Heise wrote:
:Someone noted elsethread the great variation in user requirements, :and the choice between dynamos and rechargeables is certainly :affected by them. I need a light only infrequently, so for me a :dynamo would largely be wasted weight and clutter on the bike. On Ah, but it would just work. Get on the bike, and ride. a rechargable light would have to be found, put on the bike, and discover the batteries are dead. -- sig 77 |
#37
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Dynamo/LED power conditioning
On Mon, 7 May 2018 13:21:02 +0000 (UTC),
David Scheidt wrote: Theodore Heise wrote: :Someone noted elsethread the great variation in user requirements, :and the choice between dynamos and rechargeables is certainly :affected by them. I need a light only infrequently, so for me a :dynamo would largely be wasted weight and clutter on the bike. On Ah, but it would just work. Get on the bike, and ride. a rechargable light would have to be found, put on the bike, and discover the batteries are dead. Sure, I get that--and don't disagree. But for me, the effort to find the light, have a charged battery, and mount it is small. I keep things in established places, and plan ahead. The risk of failure is acceptable (to me). On the other hand, I rarely need the light, and like having the handlebar real estate available for other things. Also, my commuter (and beater) bike has a fixed gear, and I like to keep the overall simple aesthetic for the 99% of rides for which I don't need a light. In other words, I don't commute a lot--mostly taking the fixie out during daylight hours for enjoyment. So the trade off (again, for me) is well worth it. -- Ted Heise West Lafayette, IN, USA |
#38
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Dynamo/LED power conditioning
On 5/7/2018 9:43 AM, Theodore Heise wrote:
On Mon, 7 May 2018 13:21:02 +0000 (UTC), David Scheidt wrote: Theodore Heise wrote: :Someone noted elsethread the great variation in user requirements, :and the choice between dynamos and rechargeables is certainly :affected by them. I need a light only infrequently, so for me a :dynamo would largely be wasted weight and clutter on the bike. On Ah, but it would just work. Get on the bike, and ride. a rechargable light would have to be found, put on the bike, and discover the batteries are dead. Sure, I get that--and don't disagree. But for me, the effort to find the light, have a charged battery, and mount it is small. I keep things in established places, and plan ahead. The risk of failure is acceptable (to me). On the other hand, I rarely need the light, and like having the handlebar real estate available for other things. Also, my commuter (and beater) bike has a fixed gear, and I like to keep the overall simple aesthetic for the 99% of rides for which I don't need a light. In other words, I don't commute a lot--mostly taking the fixie out during daylight hours for enjoyment. So the trade off (again, for me) is well worth it. Sure, YMMV. About keeping things in established places: I've always been big on that. Another (ahem) person in this house is much more creative and spontaneous with her storage, which is why I frequently help her find things. ;-) But one good cycling friend of mine lived (before retiring) 1/4 my distance from where we both worked. He had very low-traffic streets to get him to work. Yet he always drove, despite frequently bitching about the lack of parking places. When I asked why not ride the bike, he said "I have to find the bungee cords to hold my briefcase on the rack, find my helmet, find the pants clips or change my pants - it takes too much time." I thought that was kind of lame. Whatever I need is on my bike, ready to go. Why not? But for me, that includes the headlight and taillight. -- - Frank Krygowski |
#39
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Dynamo/LED power conditioning
On Mon, 7 May 2018 13:21:02 +0000 (UTC), David Scheidt
wrote: Theodore Heise wrote: :Someone noted elsethread the great variation in user requirements, :and the choice between dynamos and rechargeables is certainly :affected by them. I need a light only infrequently, so for me a :dynamo would largely be wasted weight and clutter on the bike. On Ah, but it would just work. Get on the bike, and ride. a rechargable light would have to be found, put on the bike, and discover the batteries are dead. Assuming you own an automobile, what do you check before you go for a ride or drive? Got enough gasoline? Fluid levels within limits? Tire pressure look normal? Engine warning light on? For fanatics, does the add-on OBD II display panel show anything unusual? Having driven rolling wrecks during college, walking around the vehicle to see what has fallen off or was stolen in the night was a regular ritual. Same with my bicycles. Do you check the air pressure in your tires before riding? I don't, but I give the tires a good squeeze as a crude pressure check and pump as needed. My favorite mistakes are a loose quick release, a loose nut from an unfinished repair, and my folding pedals in the folded position. I take a quick look at the frame and gears for any sign of damage. I check for my seat bag of tricks, which contains tools, parts, munchies, and a few dollars. Batteries do not provide a visual or mechanical indication of SoC (state of charge), but you can add something like this: https://www.ebay.com/itm/Lithium-ion-Charging-Battery-Voltage-Capacity-Percent-Level-LED-Indicator-18650/181692946263 Some headlights have a similar indicator built in. I use a DVM (digital voltmeter) instead. More problematic is the tail light, which usually runs on alkaline AA or AAA cells. I haven't seen one with a SoC indicator and would not expect to see one as the added circuitry and display would probably cost more than the tail light. So, I run the alkalines until they die, and carry a few spare NiMH cells which I rotate as needed. With LSD (low self discharge) NiMH cells, they remain mostly charged for months. While just jumping onto the bicycle and going for a ride is a nice thought, the reality is that we all do some manner of pre-flight check before riding. So, why is it so painful to add a headlight battery test to the checklist? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#40
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Dynamo/LED power conditioning
On Mon, 7 May 2018 03:46:21 -0000 (UTC), bob prohaska
wrote: Joerg wrote: Why should bicycle lighting be inferior to car lighting? Does anybody make a bicycle dynamo that produces more than 3 watts at 10 mph? I couldn't find any, but they might exist. What I found were plenty that claimed as high as 15 watts, but didn't bother mentioning what rpm, mph, or kph was required. How much more power do you need or want? 10 mph = 16 kph From the graphs: http://www.myra-simon.com/bike/dynotest.html at 16 kph, the range of output power is 2.5 to 3.4 watts. Notice how the power curves all flatten out as the power increases. This is intentional as it prevents blowing up the incandescent lamp filament with too much voltage at high speeds. It's one by designing the dynamo windings so that the core saturates at some load point. Spin the dynamo faster, and the voltage remains roughly constant. If you want more power, you'll need both a bigger or stronger magnet, and either a different grade of steel for the armature or just more steel: https://en.wikipedia.org/wiki/Electrical_steel With a hub dynamo, you're kinda stuck with the available products, most of which max out at 3 watts at 10 mph. You could make something in a larger hub or just find a SMALL eBike hub motor that can be wired as a generator or dynamo. Maybe something like this: https://www.alibaba.com/product-detail/Hot-Sale-24v-36v-48v-The_60740001136.html but without the internal brake and 3 speed gearing. With roller or bottle generators that are driven by the tire, all you need are two generators running in parallel (with isolation diodes if they are not identical). Double the power, double the output, and double the drag. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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