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#51
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Veloloop Triggers Inductive Road Sensors
On Sat, 11 Oct 2014 12:12:24 -0700, Jeff Liebermann
wrote: On Sat, 11 Oct 2014 18:14:46 +0700, John B. Slocomb wrote: The permanent magnets in the front wheel hub generator? Nope. Too far away from the loop and not enough mass. Also, see my reply to Frank K. If the rims are what the loop is detecting, then perhaps it's not so much the permeability of the bicycle frame that's important, but rather that there be a shorted turn loop somewhere in the system. I'm kinda floundering around with more ideas than results right now because I don't have a vehicle detector that I can use for testing. They seem cheap enough used on eBay, so I may throw some money at the problem. MRIN (More Research Is Necessary). Or maybe a larger generator, with really big magnets, which could have a ancillary use as power for the (apparently) universally required high intensity lights :-) It doesn't work by magnetism and the detector is not a WWII style German magnetic mine that detects the residual magnetism of ships and bicycles that might float past. Are you sure? I'm thinking of tuned coils in a radio or the coil on a metal detector which are essentially part of a tuned circuit. Put something near the coil changes its inductance and alters the frequency. Modern metal detectors can tell the difference between a doubloon and a coke bottle cap :-) Re magnetism, I somehow seem to have the recollection that putting a magnet close to a tuned circuit changes things... or is that just that it is big chunk of metal? -- Cheers, John B. |
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Veloloop Triggers Inductive Road Sensors
On Sun, 12 Oct 2014 11:27:06 +0700, John B. Slocomb
wrote: On Sat, 11 Oct 2014 12:12:24 -0700, Jeff Liebermann wrote: On Sat, 11 Oct 2014 18:14:46 +0700, John B. Slocomb wrote: The permanent magnets in the front wheel hub generator? Nope. Too far away from the loop and not enough mass. Also, see my reply to Frank K. If the rims are what the loop is detecting, then perhaps it's not so much the permeability of the bicycle frame that's important, but rather that there be a shorted turn loop somewhere in the system. I'm kinda floundering around with more ideas than results right now because I don't have a vehicle detector that I can use for testing. They seem cheap enough used on eBay, so I may throw some money at the problem. MRIN (More Research Is Necessary). Or maybe a larger generator, with really big magnets, which could have a ancillary use as power for the (apparently) universally required high intensity lights :-) It doesn't work by magnetism and the detector is not a WWII style German magnetic mine that detects the residual magnetism of ships and bicycles that might float past. Are you sure? No, I'm not certain. I need to play with the real thing to get a better idea of how it works, what it wants to see, how much range, why steel works better than aluminum, and the effects of mass, size, material, speed, proximity, etc. I'm thinking of tuned coils in a radio or the coil on a metal detector which are essentially part of a tuned circuit. Put something near the coil changes its inductance and alters the frequency. Modern metal detectors can tell the difference between a doubloon and a coke bottle cap :-) Vehicle detectors work on the same principle. However, I don't think they can count the change in your pockets quite yet. Re magnetism, I somehow seem to have the recollection that putting a magnet close to a tuned circuit changes things... or is that just that it is big chunk of metal? It's not magnetism. If it relied solely on magnetism, the non-ferrous, non-magnetic aluminum frame and rims would not work at all. My semi-astute guess(tm) is that it is the "shorted turn" effect, which sucks power from the oscillator loop, and produces a change in oscillator frequency and current. The shorted turn could be the wheel rims, the triangular frame, or any conductive loop of wire. The problem is that if that was the only effect, any loop of wire or metal of the same size should have the same effect. Since a steel frame and rims have a bigger effect than an aluminum frame and rims, something else is involved. It might be the mass of the material. There's also the opposing effects of eddy currents in the loop, which negate the effects of the increase in inductance caused by the ferrous metal. This ain't simple. In short, I don't understand exactly how it works and the more I read and think about the problem, the less I understand. I'll surely need to do some more reading, experiment with a real installation, and of course, continue guessing. However, first I need to get Frank K. a loop finder, which I promised about 2 months ago. http://www.fhwa.dot.gov/publications/research/operations/its/06108/02.cfm Equation 2-6 shows that iron, with a relative permeability greater than one, will increase the loop inductance. Although the greatest increase in inductance occurs when an iron core passes directly through the loop, the iron mass of a vehicle engine, transmission, or differential will slightly increase the loop inductance. This condition is called the "ferromagnetic effect." FERROMAGNETIC EFFECT AND VEHICLE DETECTION However, the ferromagnetic effect produced by the iron mass of the engine, transmission, or differential does not create a presence or passage indication by the controller. When the heavy ferrous engine enters the inductive loop's detection area, it increases the inductance of the wire loop. This effect occurs because the insertion of any iron core into the field of any inductor reduces the reluctance (i.e., a term that corresponds to the resistance of a magnetic circuit) of the flux path and, therefore, increases the net inductance. However, the peripheral metal of the vehicle has an opposite effect on the inductance due to eddy currents that are produced. The decrease in inductance from the eddy currents more than offsets the increase from the ferrous mass of the engine, and the net effect is an overall reduction in the inductance of the wire loop. (...) BICYCLE AND MOTORIZED VEHICLE DETECTION MODELS Figure 2-9 illustrates the detection of a bicycle or motorcycle by an inductive loop. These conveyances can be modeled as a vertical conducting object relative to the plane of the loop. When the cycle travels along the loop wire, eddy currents are induced in the conducting wheel rims and frame. When the cycle is directly over the loop wire, coupling between the inductive loop and the cycle is maximized. So, a bicycle detector works primarily by eddy currents (i.e. shorted turn effect). -- 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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Veloloop Triggers Inductive Road Sensors
On Sat, 11 Oct 2014 13:39:58 -0700 (PDT), Frank Krygowski
wrote: On Saturday, October 11, 2014 3:01:40 PM UTC-4, Jeff Liebermann wrote: On Fri, 10 Oct 2014 21:02:31 -0700 (PDT), Frank Krygowski wrote: Other technical people with whom I've corresponded have claimed that the wheels of a bike are what are normally detected. Some have helped traffic engineers calibrate the loop detectors, by supplying a 20" wheel rim mounted on a piece of wood. Sensitivity is increased until that single spokeless rim is detected. I think they were using an aluminum rim, but I'm not sure. Did you by chance try the same test with a "split" aluminum rim? If what you say is true, then it's not so much the permeability of the material that's important, but rather that the bicycle provides a "shorted turn" loop to detune the vehicle detection coil. If that were true, then one should get exactly the same effect using a loop of light #14 AWG copper house wire, as one would with a proper aluminum rim. That would be interesting to try. Just a loop of copper or aluminum wire carried on the bicycle to trigger the traffic signal. That would be useful for non-metallic frames. Well, I haven't tried the trick at all. I read where an online friend of mine used the rim-on-a-board to help a traffic engineer calibrate loops. Some days (like today), my brain lacks the ability to see the obvious. The rim is NOT a loop as I suggested. It's a loop electrically shorted by 2 to 3 dozen spokes. A loop of copper wire is not going to act like a bicycle wheel unless I add spokes. Now, it's possible that a loop without the spokes works better than a bicycle wheel, which is what I want to test. If that works, it should be of some help for the carbon fiber machines. As Andrew noted, one could have a loop of copper wire between the rim strip and the rim itself to trigger the loop. Sounds reasonable. I suspect it might make no difference for most bikes, though, in that the aluminum rims already do that job. Guys with composite rims - and no aluminum braking surfaces - might find it helps. If the loop were tuned to approximately the oscillating frequency of the vehicle detector, it would make a big difference. That's what I would guess the circuitry in the various gizmos actually do. It starts with a loop tuned to the high end of the frequency range (200 KHz). A series of capacitors are switched across the loop to retune it to a lower frequency, eventually getting to the low end of the frequency range about (20 KHz). Find tuning between steps is done by a voltage variable capacitor, another capacitor switch with smaller steps, or a mechanical monstrosity. A loop tuned to exactly the vehicle detectors oscillator frequency will have a HUGE effect on the frequency, causing it to pull well off its normal operating frequency. But I wonder, if one loop is good, would multiple loops be better? I don't know. Offhand, my guess is no. Suppose we put ten turns of thin, insulated wire under the rim strip, with the ends electrically connected? Would that make the bike more detectable? I don't know. Offhand, I would guess that it would act like a loop of the same conductor diameter as the combination of all the thin wires. I do that with antennas all the time. It's called a "cage" antenna https://www.google.com/search?q=cage+antenna&tbm=isch where a large diameter conductor is simulated with smaller wires. As I've said, as an ME I never had to take Field Theory, so all this is like witchcraft to me. Bat wings? Lizards tongue? 10 turns of wire? Hint: RF and much of electronics is magic. The advantage that mechanical engineers have over electronic is that ME's can see what they're working with, while electronics is all done with test equipment because you can't see the electrons moving in the wires and components. In effect, EE's are no better than blind. When something happens in a mechanical device, such as a bicycle, you can see the damage, pickup the pieces, analyze what's left, and have a fair idea of what happened. With electronics, all you have is a circuit that just sits there doing nothing, with nothing left to analyze except a smoking ruin. Little wonder that cyclists are wary of introducing electronics into their lives. -- 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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Veloloop Triggers Inductive Road Sensors
On Sat, 11 Oct 2014 14:21:43 -0500, AMuzi wrote:
One might cold cap off the ends well and run a loop of stranded copper lamp cord between inner tube and a clincher tire to test that. I was thinking of using a long strip of aluminum duct tape or copper stained glass tape instead of rim tape on CF rims. https://www.google.com/search?tbm=isch&q=aluminum+duct+tape I have no idea if it will work, but it would be easy enough to try. If it really is the eddy currents in the "loops" that are the primary detection mechanism, then it should do something useful. -- 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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Veloloop Triggers Inductive Road Sensors
On Sunday, October 12, 2014 12:27:06 AM UTC-4, John B. Slocomb wrote:
Are you sure? I'm thinking of tuned coils in a radio or the coil on a metal detector which are essentially part of a tuned circuit. Put something near the coil changes its inductance and alters the frequency. Modern metal detectors can tell the difference between a doubloon and a coke bottle cap :-) Re magnetism, I somehow seem to have the recollection that putting a magnet close to a tuned circuit changes things... or is that just that it is big chunk of metal? From what I've read, a chunk of magnetic iron works exactly as well as a chunk of non-magnetic iron. - Frank Krygowski |
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Veloloop Triggers Inductive Road Sensors
On Sunday, October 12, 2014 2:40:11 AM UTC-4, Jeff Liebermann wrote:
On Sat, 11 Oct 2014 14:21:43 -0500, AMuzi wrote: One might cold cap off the ends well and run a loop of stranded copper lamp cord between inner tube and a clincher tire to test that. I was thinking of using a long strip of aluminum duct tape or copper stained glass tape instead of rim tape on CF rims. https://www.google.com/search?tbm=isch&q=aluminum+duct+tape I have no idea if it will work, but it would be easy enough to try. If it really is the eddy currents in the "loops" that are the primary detection mechanism, then it should do something useful. Another couple facts that may or may not prove useful: I used to do some work with inductive proximity sensors, which are roughly cigarette-sized metal gizmos with wires coming out one end (at least, in the most common configuration) that detect the presence of metal objects without contacting them. They're used on lots of production machinery, to (for example) count parts going down a production line, make sure safety gates are closed, etc. Most are binary - either on or off. The range of detection varies based on diameter of the sensor and material being detected. Anyway, I believe that vehicle detectors are essentially huge versions of the same of the same technology. And with the inductive prox switches, they detect a chunk of steel at about triple the distance of a chunk of aluminum. However, a _thin_ bit of aluminum is detected at a much closer distance than a thick piece of aluminum. I don't know why. I'm an ME. (Who, BTW, is pretty good at understanding invisible stuff like heat flow, aerodynamics, etc. It's just the electrical field stuff that baffles me.) - Frank Krygowski |
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Veloloop Triggers Inductive Road Sensors
On Sunday, October 12, 2014 7:34:58 AM UTC+1, Jeff Liebermann wrote:
Hint: RF and much of electronics is magic. The advantage that mechanical engineers have over electronic is that ME's can see what they're working with, while electronics is all done with test equipment because you can't see the electrons moving in the wires and components. In effect, EE's are no better than blind. When something happens in a mechanical device, such as a bicycle, you can see the damage, pickup the pieces, analyze what's left, and have a fair idea of what happened. With electronics, all you have is a circuit that just sits there doing nothing, with nothing left to analyze except a smoking ruin. Not blind if you know what you're doing. In the first instance, you can tell a great deal from the colour of the smoke, its amount, and of course its precise location, The first thing NOT to do is to hit the off-switch. You now have preserved the conditions that led to the indicative smoke and you can apply probes and discover what caused the failure much easier than if you switched off. Of course, if the voltage is higher than the 5V or 12V or 18V of most electronics, stuff you can put on your tongue, live, if the current isn't too high, you need to be careful, and if you're working with high tension above the household range, or up to 2000V for thermionic vacuum tube electronic power supplies, you want specialized equipment and protection as well. Also, I can tell you from the days I built my own HT vacuum tube hi-fi equipment, you want a calm demeanor. Excitable people hurt themselves in high tension electronics. (1) Little wonder that cyclists are wary of introducing electronics into their lives. Electronics is an art. Some Chinese electronics, and some German ones too, and very often Italian ones, aren't artfully made though. The faults are mechanically introduced in the production process (for instance by cheapening components, case weights and reinforcements), not in the electronic design.. But it would be foolish and idle to deny that a bottom bracket, for instance, is a great deal less likely to give trouble than bicycle electronics... Andre Jute (1) It isn't true that I broke up my signature kilovolt-plus amp because it frightened even me ****less. The bloody thing had so many windings (transformers for power, chokes, input, interstage and output), that it needed four large men to lift one channel of it, and I couldn't find any rated power connectors that didn't cost aircraft carrier money. I built it anyway just to show I could, and max output in my service always was with power choked back over 98%; because of being operated on a tiny tangent of an already very flat transfer curve, it offered an exceptionally pure sound. It's input amp (technically a booster power amp) was a 300B which itself makes a stunningly pure amp and is still available for amateurs with the money and the skill to build: it's my famous Type 39 KISS 300B on this page: http://www.audio-talk.co.uk/fiultra/...0ON%20AMPS.htm -- it works on a modest 500V out of the power transformer. |
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Veloloop Triggers Inductive Road Sensors
On Sun, 12 Oct 2014 06:59:24 -0700 (PDT), Frank Krygowski
wrote: I used to do some work with inductive proximity sensors, which are roughly cigarette-sized metal gizmos with wires coming out one end (at least, in the most common configuration) that detect the presence of metal objects without contacting them. They're used on lots of production machinery, to (for example) count parts going down a production line, make sure safety gates are closed, etc. Most are binary - either on or off. The range of detection varies based on diameter of the sensor and material being detected. I did that when I did industrial control at one of the local fruit caning plants. Most of the job consisted of cleaning rotting peaches out of the relays and connectors. The production line had a collection of metal can proximity detectors. Most were set for a range of 5 cm or less. Setting those up was someone else's job, so I didn't get any experience with them. They would have made rather poor bicycle detectors. Anyway, I believe that vehicle detectors are essentially huge versions of the same of the same technology. Agreed. Probably quite similar. And with the inductive prox switches, they detect a chunk of steel at about triple the distance of a chunk of aluminum. However, a _thin_ bit of aluminum is detected at a much closer distance than a thick piece of aluminum. That's odd. Skin effect, even at 60 Khz will keep the signal near the surface of the block or strip of aluminum. Therefore, the larger the surface area, I would guess(tm) the greater the effect. However, if my guess(tm) is wrong, then I'm either missing something, or something else is happening. I just ordered a cheap vehicle detector: http://www.ebay.com/itm/171485937758 $33.40 It's not up to municipal standards, but should be sufficient for my tinkering. Since the road in front of my house is mine, I can bury a loop in it to provide a rather realistic test. I plan to initially lay the loop on my deck or bury it in the dirt before trashing the road. I really don't need yet another project, but I should have time to at least throw together the traffic loop locator that I've been promising and run a few frame and rim tests. I don't know why. I'm an ME. (Who, BTW, is pretty good at understanding invisible stuff like heat flow, aerodynamics, etc. It's just the electrical field stuff that baffles me.) Thermo and aero can still be visualized with mechanical analogies. So can most common electrical and electronic principles. However, things tend toward magic when discussing fields and radio. Maxwell's Equations are what relate easily visualized electricity with magical fields. http://en.wikipedia.org/wiki/Maxwell's_equations I'm not even sure I understand them myself. I'm not very good with the theory as I'm mostly into using the results in applications and troubleshooting. You don't need to understand how a bicycle operates in order to ride one. -- 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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Veloloop Triggers Inductive Road Sensors
Any sufficiently advanced technology is indistinguishable from magic\\
https://www.google.com/?tbm=pts&gws_... +LOOP+SENSORS |
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Veloloop Triggers Inductive Road Sensors
https://www.google.com/?tbm=pts&gws_... +LOOP+SENSORS
Jay, run this thru a WEST search wudja ? https://www.google.com/#q=LEGAL+CHAL...SIGNAL+CONTROL |
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