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#121
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SIX thousand and FIVE hundred lumens !!!!!!!!!!
On Sun, 7 Oct 2018 17:38:21 -0400, Frank Krygowski
wrote: My favorite photo of him was taken when he was one year old. He couldn't yet talk. But completely on his own, he grabbed a phillips screwdriver from his dad's tool box, toddled over to his cousin's bike, plugged the screwdriver into a phillips screw on the bike and tried to loosen it. I snapped the photo and still have it on my refrigerator. Very cool. Keep encouraging the kid. However, I have a sad story. My guess is about 1984. I learned programming from a friend in exchange for taking care of his computers. He ran a business doing custom database programs and had a house full of DEC, NCR, and Plexus computers. He needed me because he literally could not operate a screwdriver. At first, I didn't believe that it was possible, so I tried and failed to teach him to work with some basic hand tools. Such things must be learned at an early age. His father had been an auto mechanic and didn't want his son to also become an auto mechanic. So, every time his son would pickup a tool, he would take it away from him. The result is predictable. He became a very good programmer, but was useless when it came to working with the hardware. -- 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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#122
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SIX thousand and FIVE hundred lumens !!!!!!!!!!
On Sun, 7 Oct 2018 20:37:59 -0700, sms
wrote: On 10/1/2018 6:29 PM, Jeff Liebermann wrote: snip Let's see what the package can do as a heat sink. Latent heat for aluminum is 0.900 Joules/gm-K. The light weighs 142 grams, which I'll assume is mostly aluminum. The light dissipates 71 watts with all the LED's turned on. I would guess that 75C would be uncomfortably warm for both the electronics and the bicycle rider. That's a temp rise of 50C (50K). Joules = Watts * seconds = 71 watts * seconds. Therefo 0.900 = 71 * seconds / (142 * 50) Time(sec) = 900 seconds = 15 min Not too horrible. One has 15 minutes of full brightness lighting, in still air, before the LED's burn your hand or cause a thermal shutdown. They even admit that full power requires sufficient airflow requiring moderate speed to prevent throttling. Yes, and they little to improve radiation cooling by increasing the surface area. A long time ago, one poster here was insisting that one reason LED lights were so wonderful was the lack of a "white-hot filament." What he failed to understand was that a high wattage LED has a very hot semiconductor junction and that extracting the heat from that junction is a very difficult process, more difficult than cooling an incandescent or HID lamp. Some LED lights for cars even have fans as part of the thermal solution. It doesn't matter how the heat is generated. It could be a carbide lantern producing the heat, and it still needs to be radiated or conducted away somewhere. Still waiting for liquid cooled bicycle lights. I was over at the Computer History Museum last week where they have several liquid coold computers on display. "liquid cooled 500W LED bike lamp" https://www.youtube.com/watch?v=hYxrpHTEEEQ (6:23) 40,000 lumens. I suppose that dumping hot water on the trail would work for a while. Otherwise, collect the hot water and use it to make coffee during the ride. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#123
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SIX thousand and FIVE hundred lumens !!!!!!!!!!
On Sun, 07 Oct 2018 21:46:39 -0700, Jeff Liebermann
wrote: Yes, and they little to improve radiation cooling by increasing the surface area. That should read: Yes, and they did little to improve radiation cooling by increasing the surface area. "liquid cooled 500W LED bike lamp" https://www.youtube.com/watch?v=hYxrpHTEEEQ (6:23) 40,000 lumens. I suppose that dumping hot water on the trail would work for a while. Otherwise, collect the hot water and use it to make coffee during the ride. I'm not thinking clearly tonite. Never mind making coffee. Add a steam engine or turbine and use the waste heat and steam to power the bicycle. That would make it an sBike (steam bike). High power LED's are about 20% efficient (self heating really reduces efficiency), so 80% of the 500 watts of input power goes into waste heat. That's 400 watts of heat to power the bicycle. If you don't need or want an sBike, replace the steam engine or turbine with an alternator to generate electricity to power the light (co-generation) and it help produce some more runtime. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#124
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SIX thousand and FIVE hundred lumens !!!!!!!!!!
Jeff Liebermann wrote:
Also, one other minor thing. When someone takes the time to explain how something works, I suggest you not repackage what they provided and ask them if that's is what they meant. Doing that is a trick that students sometimes do to reverse the situation on their instructors. Instead of the instructor asking questions, and the student providing an explanation or answer, the student ask the instructor the same question repackaged, and in effect tests if the instructor understands the question. The process does not demonstrate that you've learned anything more than rearranging a question. What is happening is the instructor is using words, phrases and presents a flow of thoughts and maybe half of that is understood/followed by the student. The student tries to explain the same thing, but in a language and mindset he/she understands and recognizes, and organizes the material in a way that makes more sense for him/her. E.g., Instructor: The sum of 5 and 4 is 9. Student: You mean if you add 4 to 5, you get 9? Instructor: Yes. What has happened? Then student has understood what is going on, so he or she can sleep at night, AND s/hes given a chance to acquire proper terminology. When you own a tool or piece of technology it is often very easy to understand what it does and how it works.. But explaining it to someone who doest have it, maybe never saw ti, is much more difficult. -- underground experts united http://user.it.uu.se/~embe8573== |
#125
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SIX thousand and FIVE hundred lumens !!!!!!!!!!
On 10/7/2018 9:46 AM, Jeff Liebermann wrote:
Actually, I know of several. However, they don't deal with literally everything that walks in the front door. They work out of their garages and tend to specialize in various areas. Within the general area where I live, we have repair "shops" for string instruments, music keyboards, computahs, machine tools, bicycles, mechanical clocks, etc. They're still around, but because the cost of maintaining a walk-in store front and hiring employees is so high, they work out of their houses. But not a general repair shop. We went over to Santa Cruz a few years ago to buy a saxophone from a garage shop. He imports used saxophones from Japan, repairs them, and resells them, as well as repairing woodwind instruments. He said that the instruments from Japan usually need very little work, maybe some new pads. It's quite a business, selling used instruments for about 2/3 the cost of a new one, and probably paying 1/3 or less. When we got there he had just sold our first choice to UCSC. http://stevegraysaxes.com/ Closer to me we have a woodwind repair place operated out of a spare bedroom in a house. He'll do simple repairs while you wait. The local music store charges about 5x, is not as skilled, and has a long wait time. |
#126
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SIX thousand and FIVE hundred lumens !!!!!!!!!!
On 10/7/2018 9:46 AM, Jeff Liebermann wrote:
snip Nice. There's another difference. He had years of experience, while you seem to be limiting yourself to what you can learn from a garage full of old bicycles and parts. That works, to a point, but I think you will do much better either working for someone else in order to learn the trade, or working on a better class of bicycle. For bicycle lighting, there is a difference between cheap junk and a light designed specifically for a type of bicycle riding. Or, perhaps building a clone of a high end bicycle light might be ummm... enlightening. You can buy all the components on eBay. Never mind what it looks like, build it in a wooden box. Do not build a high-performance bicycle light in a wooden box! There's a reason why high-performance bicycle lights use aluminum enclosures, the thermal solution is the most difficult part of efficient electronics design, whether it's laptops, phones, mainframes, or bicycle lights. |
#127
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SIX thousand and FIVE hundred lumens !!!!!!!!!!
On 2018-10-07 17:08, John B. Slocomb wrote:
On Sun, 7 Oct 2018 15:02:19 -0400, Frank Krygowski wrote: On 10/6/2018 2:49 PM, Joerg wrote: [...] 2. It causes oncoming motorists to see the cyclist much earlier and, for example, if a big semi comes they can pull a bit to the right so the semi can give the cyclist wide berth. I do NOT believe any practical light allows a motorist to see a cyclist _much_ earlier. In almost every case, I've seen on-road cyclists before I noticed that they had a light. And in no case did I see the light early enough to make any practical difference. You're fixating on a superstitious talisman, imagining benefits that don't exist in real life. I think I've mentioned seeing the bloke on a bike wearing bright orange knee socks nearly a kilometer away :-) I remember the orange socks but can't remember whether he had a light on his bike or not :-) I wonder what the reaction would be if said bloke participated in a business meeting wearing bright orange knee socks. -- Regards, Joerg http://www.analogconsultants.com/ |
#128
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SIX thousand and FIVE hundred lumens !!!!!!!!!!
On 10/1/2018 7:18 PM, Emanuel Berg wrote:
Jeff Liebermann wrote: Ok, let's do the math. I put a flashlight to the handlebars the other day with re-openable cable ties. It seems to work OK, a pretty solid fix. I cut the cable ties with a combination plier so it looks neat as well. The flashlight is 3*AAA batteries with 9 diodes. How many lumens is that, do you think? I think I should get a proper bicycle light soon tho. The problem with 3AA batteries is that the run-time of a reasonably powered light would be very low. There are a few lights with 3AA batteries. but not many. By the time you buy rechargeable NiMH cells, a charger, a suitable light, you may as well buy a purpose-built bicycle light. I picked up a light at Interbike on the last day (when the exhibitors try to sell the booth demos so they don't have to ship them back). I actually didn't save much but I got it right away. https://www.aliexpress.com/item/GACIRON-professional-Bicycle-Light-Power-Bank-Waterproof-USB-Rechargeable-Bike-Light-Side-Warning-Flashlight-1600-Lumen/32802747811.html There are a couple of good features that I like. The "breathe mode" is a good daytime running light, lower power and not a strobe, but a modulated pattern. It can be used to charge a phone via the USB-A port. It is charged via MicroUSB. 1600 lumens is sufficient for road riding. I also have a dynamo light on the bike but it's not really sufficient for very dark paths. |
#129
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SIX thousand and FIVE hundred lumens !!!!!!!!!!
On 10/8/2018 11:34 AM, sms wrote:
snip There are a couple of good features that I like. The "breathe mode" is a good daytime running light, lower power and not a strobe, but a modulated pattern. It can be used to charge a phone via the USB-A port. It is charged via MicroUSB. I also like that they sell extra mounting brackets fairly inexpensively so you can use one light on multiple bikes without having to move the mount between bikes. https://www.aliexpress.com/item/GACIRON-Universal-Bicycle-Handlebar-Mount-Cell-Phone-GPS-Holder-with-3M-Back-Sticky-Pad-for-Smart/32795618775.html |
#130
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SIX thousand and FIVE hundred lumens !!!!!!!!!!
On Mon, 8 Oct 2018 08:53:19 -0700, sms
wrote: On 10/7/2018 9:46 AM, Jeff Liebermann wrote: snip Nice. There's another difference. He had years of experience, while you seem to be limiting yourself to what you can learn from a garage full of old bicycles and parts. That works, to a point, but I think you will do much better either working for someone else in order to learn the trade, or working on a better class of bicycle. For bicycle lighting, there is a difference between cheap junk and a light designed specifically for a type of bicycle riding. Or, perhaps building a clone of a high end bicycle light might be ummm... enlightening. You can buy all the components on eBay. Never mind what it looks like, build it in a wooden box. Do not build a high-performance bicycle light in a wooden box! The package might have an effect on cooling the LED and electronics, but that's not an issue here, where a proper beam footprint and battery life are more important. The exercise will be in optics, current regulation, beam pattern optimization, measurements, testing, and the reality of such mundane problems such as high resistance battery contacts, lossy components, junk eBay electronics, etc. I agree that thermal management is important, but that can be done later or when a proper package has been designed. Think of it more like an optical bench than a streamlined finished product. Well, maybe you're right. Instead of a wooden box, substitute an aluminum mini-box to take advantage of better heat dissipation: https://www.google.com/search?q=cast+aluminium+box&tbm=isch Or maybe a plastic box with a clear cover so he can better see what's happening inside: https://www.google.com/search?tbm=isch&q=plastic+project+box+clear+cover Remember, the uglier the construction, the better it will work. There's a reason why high-performance bicycle lights use aluminum enclosures, the thermal solution is the most difficult part of efficient electronics design, whether it's laptops, phones, mainframes, or bicycle lights. Yep. I've seen a few high power bicycle light prototypes with built in fans to cool the LEDs. Also, one with an scoop air intake for improved internal air flow. LED output is higher at lower temperatures. You might be amused with the various flashlight forums for the latest in high fashion, errr... high performance lighting: https://www.candlepowerforums.com http://budgetlightforum.com Copper packaging and cooling has been fashionable for about 2 years. Never mind that a metallic copper finish is a worse heat radiator than an anodized black aluminum finish. Of course, some of these are copper plated or painted aluminum: https://www.google.com/search?q=copper+flashlight&tbm=isch Sometimes, the original reason for using copper is lost and the fashion thing takes over: https://www.edcforums.com/threads/show-your-flashlight-patina.127703/ Sigh. Anyway, I would be quite satisfied if Emanuel Berg were to build something resembling a bicycle light from scratch, measures the lumens, lux, candelas, beam pattern, variation in intensity across the beam pattern, power draw, operating temperature, and then improves the design updating the measurements as he makes changes. -- 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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