#131
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More About Lights
On Wed, 15 Mar 2017 15:14:56 +1100, James
wrote: On 15/03/17 13:43, Jeff Liebermann wrote: On Tue, 14 Mar 2017 07:54:26 -0700, Joerg wrote: On 2017-03-13 20:00, Jeff Liebermann wrote: On Mon, 13 Mar 2017 12:38:07 -0700, Joerg wrote: 55V at 500mA. This is encouraging. That's 27.5 watts out of a 3 watt dynamo. I was impressed, until I converted 136 km/hr and found that it was 84.5 mph. With a rocket assisted bicycle, I might be able to do that. Well, yeah, they just wanted to see where the limit is. I guess the enameled copper wire inside would smoke out if you kept that speed for long. Only the resistive part dissipates power in the wi P = I^2 * R = 0.5^2 * 2 = 0.5 watts So, it won't be the wire that gets hot. However, the cores in saturation are going to get warm. Offhand, I don't know how to calculate how hot. Do you mean eddy currents in the core? Nope. I meant hysteresis losses. Eddy currents do contribute to losses by "bucking" the build up and collapse of the magnetic field, but most of the heat is produced by hysteresis losses: https://www.quora.com/What-is-hysteresis-loss-Where-does-the-loss-actually-occur See an induction heater or stove for an extreme case of heat being generated by eddy and hysteresis currents: https://en.wikipedia.org/wiki/Induction_heating -- 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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#132
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More About Lights
On 15/03/17 16:15, Jeff Liebermann wrote:
On Wed, 15 Mar 2017 15:14:56 +1100, James wrote: On 15/03/17 13:43, Jeff Liebermann wrote: On Tue, 14 Mar 2017 07:54:26 -0700, Joerg wrote: On 2017-03-13 20:00, Jeff Liebermann wrote: On Mon, 13 Mar 2017 12:38:07 -0700, Joerg wrote: 55V at 500mA. This is encouraging. That's 27.5 watts out of a 3 watt dynamo. I was impressed, until I converted 136 km/hr and found that it was 84.5 mph. With a rocket assisted bicycle, I might be able to do that. Well, yeah, they just wanted to see where the limit is. I guess the enameled copper wire inside would smoke out if you kept that speed for long. Only the resistive part dissipates power in the wi P = I^2 * R = 0.5^2 * 2 = 0.5 watts So, it won't be the wire that gets hot. However, the cores in saturation are going to get warm. Offhand, I don't know how to calculate how hot. Do you mean eddy currents in the core? Nope. I meant hysteresis losses. Eddy currents do contribute to losses by "bucking" the build up and collapse of the magnetic field, but most of the heat is produced by hysteresis losses: https://www.quora.com/What-is-hysteresis-loss-Where-does-the-loss-actually-occur See an induction heater or stove for an extreme case of heat being generated by eddy and hysteresis currents: https://en.wikipedia.org/wiki/Induction_heating Hysteresis losses are different from saturation. Saturation shouldn't occur if the core has been adequately designed to accommodate all the permanent magnet flux & MMF. -- JS |
#133
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On Wed, 15 Mar 2017 16:45:57 +1100, James
wrote: On 15/03/17 16:15, Jeff Liebermann wrote: On Wed, 15 Mar 2017 15:14:56 +1100, James wrote: On 15/03/17 13:43, Jeff Liebermann wrote: On Tue, 14 Mar 2017 07:54:26 -0700, Joerg wrote: On 2017-03-13 20:00, Jeff Liebermann wrote: On Mon, 13 Mar 2017 12:38:07 -0700, Joerg wrote: 55V at 500mA. This is encouraging. That's 27.5 watts out of a 3 watt dynamo. I was impressed, until I converted 136 km/hr and found that it was 84.5 mph. With a rocket assisted bicycle, I might be able to do that. Well, yeah, they just wanted to see where the limit is. I guess the enameled copper wire inside would smoke out if you kept that speed for long. Only the resistive part dissipates power in the wi P = I^2 * R = 0.5^2 * 2 = 0.5 watts So, it won't be the wire that gets hot. However, the cores in saturation are going to get warm. Offhand, I don't know how to calculate how hot. Do you mean eddy currents in the core? Nope. I meant hysteresis losses. Eddy currents do contribute to losses by "bucking" the build up and collapse of the magnetic field, but most of the heat is produced by hysteresis losses: https://www.quora.com/What-is-hysteresis-loss-Where-does-the-loss-actually-occur See an induction heater or stove for an extreme case of heat being generated by eddy and hysteresis currents: https://en.wikipedia.org/wiki/Induction_heating Hysteresis losses are different from saturation. Saturation shouldn't occur if the core has been adequately designed to accommodate all the permanent magnet flux & MMF. Most (not all) dynamos are designed to provide some form of self-regulation. This made sense back in the days when the load was just a simple 6v incandescent light bulb. It wouldn't do to have Kamakazi downhill speeders producing enough revolutions to have the dynamo belch 12VAC and burn out the bulb. Fast forward to today, and we no longer use incandescent lights on dynamos. Most (not all) LED lamps have built in regulators and really don't need to have the dynamo perform any additional regulation. However, the industry is conservative, and things change very slowly. Kinda like the automobile industry requiring 25 years to get rid of the buggy whip socket. So, we still have dynamos that intentionally designed to NOT produce a linear increase in output for high RPMs. Fortunately, the problem is not universal. http://www.pilom.com/BicycleElectronics/HubDynamo.htm Notice the 2nd graph of Hub vs Bottle Power. The Shimano DH-3D71 hub dynamo produces a linear increase in output power with no saturation visible. (However, at my cruising speed of 15 km/hr, it only produces 4 watts and is therefore only a slight improvement over the common bottle dynamo). Hystersis loss is core saturation loss. What happens is that at some point, adding additional current to the coil and core does produce an increase in the magnetic field. Magnetic domains will change direction when current is applied, but are not terribly thrilled with the idea. Their resistance to this change in current and direction is hysteresis loss. This additional current (and power) has to go somewhere since it can't be used to build a changing magnetic field. So, it gets converted into heat. Eddy current losses are the result of changes in magnetic field, not changes in applied current. When the magnetic field finally decides to change direction and AFTER hysteresis losses are produced, the resultant magnetic field breaks up into small magnetic loops or eddys. Adjacent eddys fight each other resulting in repulsion. The energy required to overcome this repulsive force are the eddy current losses. As I understand it, the favored core material is some form of mu-metal or permalloy which saturate nicely at low currents: https://en.wikipedia.org/wiki/Mu-metal I'm not sure this is the material as some description suggest that it's "cold rolled dynamo silicon sheet steel" or the same stuff used in the E/I laminations of a common AC power transformer. It's after midnight. I give up for tonite. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#134
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More About Lights
On Wednesday, March 15, 2017 at 3:07:41 AM UTC-4, Jeff Liebermann wrote:
On Wed, 15 Mar 2017 16:45:57 +1100, James wrote: On 15/03/17 16:15, Jeff Liebermann wrote: On Wed, 15 Mar 2017 15:14:56 +1100, James wrote: On 15/03/17 13:43, Jeff Liebermann wrote: On Tue, 14 Mar 2017 07:54:26 -0700, Joerg wrote: On 2017-03-13 20:00, Jeff Liebermann wrote: On Mon, 13 Mar 2017 12:38:07 -0700, Joerg wrote: 55V at 500mA. This is encouraging. That's 27.5 watts out of a 3 watt dynamo. I was impressed, until I converted 136 km/hr and found that it was 84.5 mph. With a rocket assisted bicycle, I might be able to do that. Well, yeah, they just wanted to see where the limit is. I guess the enameled copper wire inside would smoke out if you kept that speed for long. Only the resistive part dissipates power in the wi P = I^2 * R = 0.5^2 * 2 = 0.5 watts So, it won't be the wire that gets hot. However, the cores in saturation are going to get warm. Offhand, I don't know how to calculate how hot. Do you mean eddy currents in the core? Nope. I meant hysteresis losses. Eddy currents do contribute to losses by "bucking" the build up and collapse of the magnetic field, but most of the heat is produced by hysteresis losses: https://www.quora.com/What-is-hysteresis-loss-Where-does-the-loss-actually-occur See an induction heater or stove for an extreme case of heat being generated by eddy and hysteresis currents: https://en.wikipedia.org/wiki/Induction_heating Hysteresis losses are different from saturation. Saturation shouldn't occur if the core has been adequately designed to accommodate all the permanent magnet flux & MMF. Most (not all) dynamos are designed to provide some form of self-regulation. This made sense back in the days when the load was just a simple 6v incandescent light bulb. It wouldn't do to have Kamakazi downhill speeders producing enough revolutions to have the dynamo belch 12VAC and burn out the bulb. Fast forward to today, and we no longer use incandescent lights on dynamos. Most (not all) LED lamps have built in regulators and really don't need to have the dynamo perform any additional regulation. However, the industry is conservative, and things change very slowly. Kinda like the automobile industry requiring 25 years to get rid of the buggy whip socket. So, we still have dynamos that intentionally designed to NOT produce a linear increase in output for high RPMs. Fortunately, the problem is not universal. http://www.pilom.com/BicycleElectronics/HubDynamo.htm Notice the 2nd graph of Hub vs Bottle Power. The Shimano DH-3D71 hub dynamo produces a linear increase in output power with no saturation visible. (However, at my cruising speed of 15 km/hr, it only produces 4 watts and is therefore only a slight improvement over the common bottle dynamo). Snipped -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 I remember burning out bulbs with my bottle dynamo if I rode really fast. I also remember the slipping problems when the wheels were wet even when I used the rubber boot sold to go on the bottle dynamo roller. Hub dynamos today really seem to fall down at slow speeds. Cheers |
#135
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More About Lights
Sir Ridesalot wrote:
:I remember burning out bulbs with my bottle dynamo if I rode really :fast. I also remember the slipping problems when the wheels were wet even :when I used the rubber boot sold to go on the bottle dynamo roller. Hub :dynamos today really seem to fall down at slow speeds. Mine work fine from walking speeds. They produce more light at higher speeds, but at slow speeds you don't need it, because you're not moving fast. -- sig 85 |
#136
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On Wednesday, March 15, 2017 at 7:53:52 AM UTC-7, David Scheidt wrote:
Sir Ridesalot wrote: :I remember burning out bulbs with my bottle dynamo if I rode really :fast. I also remember the slipping problems when the wheels were wet even :when I used the rubber boot sold to go on the bottle dynamo roller. Hub :dynamos today really seem to fall down at slow speeds. Mine work fine from walking speeds. They produce more light at higher speeds, but at slow speeds you don't need it, because you're not moving fast. I sometimes need light most at slow speeds, when I'm creeping up hills and trying not to fall into giant pot holes. -- Jay Beattie. |
#137
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On Wednesday, March 15, 2017 at 9:45:34 AM UTC-7, jbeattie wrote:
On Wednesday, March 15, 2017 at 7:53:52 AM UTC-7, David Scheidt wrote: Sir Ridesalot wrote: :I remember burning out bulbs with my bottle dynamo if I rode really :fast. I also remember the slipping problems when the wheels were wet even :when I used the rubber boot sold to go on the bottle dynamo roller. Hub :dynamos today really seem to fall down at slow speeds. Mine work fine from walking speeds. They produce more light at higher speeds, but at slow speeds you don't need it, because you're not moving fast. I sometimes need light most at slow speeds, when I'm creeping up hills and trying not to fall into giant pot holes. -- Jay Beattie. Where are you on Strava |
#138
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More About Lights
On Wednesday, March 15, 2017 at 12:45:34 PM UTC-4, jbeattie wrote:
On Wednesday, March 15, 2017 at 7:53:52 AM UTC-7, David Scheidt wrote: Sir Ridesalot wrote: :I remember burning out bulbs with my bottle dynamo if I rode really :fast. I also remember the slipping problems when the wheels were wet even :when I used the rubber boot sold to go on the bottle dynamo roller. Hub :dynamos today really seem to fall down at slow speeds. Mine work fine from walking speeds. They produce more light at higher speeds, but at slow speeds you don't need it, because you're not moving fast. I sometimes need light most at slow speeds, when I'm creeping up hills and trying not to fall into giant pot holes. -- Jay Beattie. Ditto. Or ride off the edge of the trail and down the side into the river. Chers |
#139
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More About Lights
On Wednesday, March 15, 2017 at 10:28:52 AM UTC-7, Sir Ridesalot wrote:
On Wednesday, March 15, 2017 at 12:45:34 PM UTC-4, jbeattie wrote: On Wednesday, March 15, 2017 at 7:53:52 AM UTC-7, David Scheidt wrote: Sir Ridesalot wrote: :I remember burning out bulbs with my bottle dynamo if I rode really :fast. I also remember the slipping problems when the wheels were wet even :when I used the rubber boot sold to go on the bottle dynamo roller. Hub :dynamos today really seem to fall down at slow speeds. Mine work fine from walking speeds. They produce more light at higher speeds, but at slow speeds you don't need it, because you're not moving fast. I sometimes need light most at slow speeds, when I'm creeping up hills and trying not to fall into giant pot holes. -- Jay Beattie. Ditto. Or ride off the edge of the trail and down the side into the river. You mean like this, except at night? https://www.youtube.com/watch?v=Fmb6OvejAC0 |
#140
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More About Lights
On 3/14/2017 9:35 PM, Jeff Liebermann wrote:
On Tue, 14 Mar 2017 10:46:19 -0400, Frank Krygowski wrote: On 3/13/2017 11:00 PM, Jeff Liebermann wrote: I was thinking of building a benchtop dynamometer sized for bicycle lighting. I don't have the equipment to calibrate it so I could measure overall efficiency, but certainly can make comparative measurements of the input power(s) required to light an oversized load or bulb. Basically, just a DC motor with a DC wattmeter on the power leads. http://www.ebay.com/itm/122373782338 (Yet another project that I'll never finish). What are you intending to measure? Input power to a bike dynamo? Ideally, overall efficiency of the lighting system and verification of the simulation and dynamo model. Mechanical power (watts) in, as simulated by an electric motor vs optical power out, measured in lumens or lux. The main exercise would be calibrating the major components so that the measurements would be accurate and meaningful. It would be something like the Friction-Facts chain and lubricant test fixture in: http://www.friction-facts.com/equipment-overview OK. You may be aware of Andreas Oehler's approach, but in case you're not, what he built was essentially a big flywheel that could be used to stand in for a bike wheel and drive a bike dynamo of any design. He used a data acquisition system to record dyno electrical output as well as angular deceleration of the flywheel. That allowed computing retarding torque resulting from the dynamo, thus (coupled with angular velocity) the power consumption. I used a much simpler method. I mounted dynamos in a frame that pivoted on the dyno's rotational axis, and used a lever arm of known length pressing on a scale. Force on the scale gave torque, and known rpm enabled calculation of power. But my method didn't include losses from the friction drive. Andreas's method does. Output power was measured electrically, in Watts. If you try to measure lumens, you'll have a much harder job, and the efficiency (lumens/Watt) of the LED will enter into things. I'm not sure you want that or not. And lux isn't a power measurement, of course, so you can't get a true efficiency that way. -- - Frank Krygowski |
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