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New 1920s Technology... Today!
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#2
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New 1920s Technology... Today!
On 4/8/2021 11:52 AM, AMuzi wrote:
https://pedalcell.com/ I note that when touting their supercapacitor, they say: "Raw Power "Volatile, Unsafe" Heavens! I wouldn't want to be unsafe! ;-) -- - Frank Krygowski |
#3
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New 1920s Technology... Today!
On 4/8/2021 8:52 AM, AMuzi wrote:
https://pedalcell.com/ At least they have the drive wheel run on the rim, not the tire. An idea I think Frank has used and recommended. But yeah, kinda pathetic overall. Mark J. |
#4
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New 1920s Technology... Today!
On 4/8/2021 8:52 AM, AMuzi wrote:
https://pedalcell.com/ LOL, I especially like the "15-20W of Power Output." Uh yeah, from the battery, but not from the dynamo. A large-screen smart phone running a GPS navigation application with the LTE or 5G radio on can exceed the 3 watt output of the dynamo. $299.99, wow! Before I clicked on the link I guessed $100 since it should cost about $50. A 3W tire-driven dynamo costs about $6. The electronics to convert 6-9VAC to 5VDC is about $1. A USB power bank is about $5. I multiplied the retail cost of the components by 8 and guessed $100. Also love how their price comparison uses the most expensive, highest quality, hub dynamo. A much better solution is to buy a rechargeable bicycle light that also functions as a USB power bank and charge that light from a dynamo. Buy one of these https://www.aliexpress.com/item/1005001507833824.html (actually it comes in a lot of 5 for $2.81), four 1N5817 diodes, and a 470uF capacitor, and hook it up to a dynamo. |
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New 1920s Technology... Today!
On Thursday, April 8, 2021 at 12:05:17 PM UTC-7, Mark J. wrote:
On 4/8/2021 8:52 AM, AMuzi wrote: https://pedalcell.com/ At least they have the drive wheel run on the rim, not the tire. An idea I think Frank has used and recommended. But yeah, kinda pathetic overall. Hey, my allergies are acting up and I just blew snot all over my keyboard! |
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New 1920s Technology... Today!
On Thu, 8 Apr 2021 12:05:13 -0700, "Mark J."
wrote: On 4/8/2021 8:52 AM, AMuzi wrote: https://pedalcell.com/ At least they have the drive wheel run on the rim, not the tire. An idea I think Frank has used and recommended. But yeah, kinda pathetic overall. Mark J. Pathetic? The idea doesn't go far enough. That was the dynamo I was thinking of when I suggested that it be used on disk wheels. The idea was to move the dynamo along the radius of the disk wheel to adjust the dynamo's rotational speed and thus obtain a constant output output voltage at any speed. Why bicycle stores sell so few dynamos: http://yehudamoon.com/comic/2017-03-15/ -- Jeff Liebermann PO Box 272 http://www.LearnByDestroying.com Ben Lomond CA 95005-0272 Skype: JeffLiebermann AE6KS 831-336-2558 |
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New 1920s Technology... Today!
On 4/8/2021 8:43 PM, Jeff Liebermann wrote:
On Thu, 8 Apr 2021 12:05:13 -0700, "Mark J." wrote: On 4/8/2021 8:52 AM, AMuzi wrote: https://pedalcell.com/ At least they have the drive wheel run on the rim, not the tire. An idea I think Frank has used and recommended. But yeah, kinda pathetic overall. Mark J. Pathetic? The idea doesn't go far enough. That was the dynamo I was thinking of when I suggested that it be used on disk wheels. The idea was to move the dynamo along the radius of the disk wheel to adjust the dynamo's rotational speed and thus obtain a constant output output voltage at any speed. Why bicycle stores sell so few dynamos: http://yehudamoon.com/comic/2017-03-15/ I miss Yehuda. :-( -- - Frank Krygowski |
#8
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New 1920s Technology... Today!
On 4/8/2021 12:05 PM, Mark J. wrote:
On 4/8/2021 8:52 AM, AMuzi wrote: https://pedalcell.com/ At least they have the drive wheel run on the rim, not the tire. snip True. And those rim drive dynamos cost a lot more than the tire-driven dynamos. But you can buy a new 700c wheel with a 3W hub dynamo (Shimano) for $125, less than the cost of a rim dynamo. For $275 you can buy a 700c front wheel with a SP (Shutter Precision) hub dynamo. 20" SP equipped ("Joule") wheels are even less, $120 to $200. but of course you don't get "Generator Drag Decoupling" (except with the SP dynamo hub that has that feature). I suspect that they've sold very few of the "Pedalcell" systems. The people this is being marketed to probably didn't even pay $299.99 for their entire bicycle. The other devices that convert the output of a dynamo to 5VDC for USB charging are being sold to people that already have a hub dynamo on their bicycles, see https://www.cyclingabout.com/list-of-hub-dynamo-power-supplies-for-usb-devices/; some of the 27 devices they list are dynamo lights that have built-in USB chargers. As I stated before, if you really want to have a dynamo charge your phone, or charge a battery pack, while also having a light that can be operated from a dynamo, it makes a lot more sense to purchase a battery-powered headlight with a USB output port, and then charge the headlight from a dynamo. Many battery-powered headlights can operate while being charged, though not all of them have this capability. For under $3 you can buy a module that converts the AC output of the dynamo to 5VDC. |
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New 1920s Technology... Today!
On 4/8/2021 5:43 PM, Jeff Liebermann wrote:
snip Pathetic? The idea doesn't go far enough. That was the dynamo I was thinking of when I suggested that it be used on disk wheels. The idea was to move the dynamo along the radius of the disk wheel to adjust the dynamo's rotational speed and thus obtain a constant output output voltage at any speed. A CVT inside the dynamo would be a better design, whether a rim, tire, or hub. But of course it's really unnecessary to have a constant voltage out. There are already dynamo powered lights with a USB port for charging devices. If someone is really going to spend $300 then they'd be better off buying a dynamo hub wheel and one of those lights, or a battery powered light that can be charged and/or operated from a dynamo. For the latter, I put together a Google Doc document that explains how to do it https://docs.google.com/document/d/1UVk_yelr5UxrcKqDtGgsHTBVa3eWoUdpqDKhbZSHO_E |
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New 1920s Technology... Today!
On Fri, 9 Apr 2021 18:02:40 -0700, sms
wrote: On 4/8/2021 5:43 PM, Jeff Liebermann wrote: snip Pathetic? The idea doesn't go far enough. That was the dynamo I was thinking of when I suggested that it be used on disk wheels. The idea was to move the dynamo along the radius of the disk wheel to adjust the dynamo's rotational speed and thus obtain a constant output output voltage at any speed. A CVT inside the dynamo would be a better design, whether a rim, tire, or hub. But of course it's really unnecessary to have a constant voltage out. I was looking for simplicity. A CVT (continuously variable transmission) is not a simple device to build into a small dynamo housing. There are already dynamo powered lights with a USB port for charging devices. If someone is really going to spend $300 then they'd be better off buying a dynamo hub wheel and one of those lights, or a battery powered light that can be charged and/or operated from a dynamo. For the latter, I put together a Google Doc document that explains how to do it https://docs.google.com/document/d/1UVk_yelr5UxrcKqDtGgsHTBVa3eWoUdpqDKhbZSHO_E Very nice but I screwed up. The DC output voltage from a bridge is NOT: DC_out = 1.414 * AC_Vrms_input More correctly, the DC output is: DC_out = 0.9 * AC_Vrms_input For the calcs, see: https://www.electronics-tutorials.ws/diode/diode_6.html For such a low voltage dynamo, the Schottky diode voltage drop should also be included in the calculations. Another problem is you're ignoring the original problem(s) and solving one that was not even mentioned (USB devices). Jay arbitrarily decided that an 800 lumen light would be nice if it could be powered by a dynamo. Without questioning the decision to specify such a high power light, I went into what is necessary to power an 800 lumen light solely on dynamo power. It was generally assumed that building a battery operated 800 lumen light, where the battery is charged by the dynamo, is possible. I later estimated the percentage of power produced by the typical cyclists at 15 mph using a commodity 3 watt dynamo light, and a higher power light suitable for delivering 800 lumens. While there was an increase in drag, it was within the abilities of most cyclists. All that was needed was a dynamo that delivered both higher output power at higher efficiency. I then arbitrarily decided that removing one of the key features of most bicycle dynamos would offer better efficiency at high RPM. The early dynamo power lights ran incandescent lamps. These lamps were very sensitive to over-voltage. Even a little over their rated maximum power, and the filament would fuse open. The resulting dynamo included an inductor (saturable reactor) which would reduce the voltage to the incandescent lamp at high RPM, where the voltage was highest. This formed a crude and cheap voltage/current regulator and is responsible for the "flat" voltage and power curve of the dynamo. What I proposed was to remove the inductors and allow the dynamo to produce more output power at high RPM. However, Frank offered a good question. Does this also improve efficiency at high RPM. I assumed that it does, but I'm not sure and won't know without some testing. Another item that was mentioned was operating the headlight at low bicycle speeds, where the dynamo is unable to deliver sufficient output. This can be in various ways such as a CVT, PWM (pulse width modulation) light dimmer to reduce the load, switch to fewer LED's, etc. Of course, a battery/dynamo hybrid will solve the problem as long as the battery can be recharged, but for now, batteries are not part of the dynamo problem. My best guess(tm) is that a higher power dynamo can only work if the losses are reduced. That means, much higher voltages, no saturable reactor regulators, very wide input range boost converter on the input, high efficiency buck converter to drive the LEDs, and high RPM for high operating frequencies (about 50KHz) so that ferrites can be used instead of powdered iron. In other words, start from scratch and design something that will drive a modern LED headlight, not an adaptation of something designed to drive an ancient incandescent light bulb. -- Jeff Liebermann PO Box 272 http://www.LearnByDestroying.com Ben Lomond CA 95005-0272 Skype: JeffLiebermann AE6KS 831-336-2558 |
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