A card compass floating in a liquid sphere with pick ups on the wall meets all the criteria.
On May 21, 8:11 am, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > 52 card pick up outside, when the wind is blowing 20 knots, doesn't > sound so good. > > Inside a cell phone the B fields might be like 20 knots and > swirling... > > 1. Only measure when quiet ie measure really fast after shutting off > all things that mess up the reading. > 2. Shield the sensor > 3. Choose a goo time constant such that persistent fields are measured > but hi frequency stuff is rejected - design a low pass filter > characteristic in the mechanical implementation of the sensor > specifically for reliable operation inside cell phones. > 4. Just use spaced accelerometers and forget magnetism - work in g's > > Anyway, good enough does not have to be expensive. It is a will > function. > > On May 21, 6:42 am, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > > > > > James, > > > It took me a while to understand what you were saying. > > > I think it would work and is incrementally free except for that > > calibration step. > > > There are concerns about effects of building when one is not in an > > open field, and the hard edges they have. > > > …A pulsed simulated MEMS birds eye might work. > > >http://www.npr.org/templates/story/story.php?storyId=90186088 > > > It feels like $1.25 to me, because it is not a dry process. (note: a 2- > > D version that does only one axis might be a lot easier to make the > > first time!) The idea is: > > > 1) create a [hemi-spherical] cavity with a tossing mechanism on the > > surface. Maybe an LED or a mechanical trampoline or an electro-magnet > > or just electrodes. > > 2) add sensors/junctions/dopants on the surface > > 3) put in simulated birds eye goop. The viscosity of the suspension > > goop and even the need for goop are TBD having to do with toss and > > catch time constants of the molecule you are tossing. I would try > > filling it with dust first, maybe iron filings (ferrite dust is less > > sticky) - do you even need magic birds eye chemicals and the > > associated energy cycle? It might be that need goes hand in hand with > > the suspension goop? > > > Anyway, the compass works in a pulsed way by tossing the magnetically > > active/polar stuff off the wall and then sensing how it lands. Toss/ > > Sense, Toss/Sense.... > > > The suspension goop might still be required to damp out the history of > > the toss before the landing occurs. > > > Goopless it is 80 cents, with goop it is $1.25. > > > Either way you can put it in an affordable handset and it will earn > > its keep in less than a month. > > > Adding your sensor fusion thought from a while ago and Peli's picture > > of an accelerometer as an indicator of 'which edge of the phone has > > the water sloshed to?' you actually get something that does work. > > > You know the direction of g from the accelerometer. > > Toss the magnetic dust up in a sphere and when it lands it will not > > land aligned exactly with the g vector. It will be displaced toward > > magnetic north. There an inexpensive compass that works good enough > > for our purposes. for $1.05 and $1.50. > > > So everybody gets phones that are perpetually playing 52 card pickup. > > > Now that that is solved, it is time to focus on compelling > > software ;-) > > > ed > > > On May 20, 8:21 am, James <[EMAIL PROTECTED]> wrote: > > > > efontana, > > > > If an existing cell phone does not have a sensor you want, then the > > > only alternatives are to make the best use of what you have available, > > > or not to provide the function at all. > > > > By using the variable signal profiling, it is useful for when a > > > dedicated compass sensor is not available in the cell phone. The > > > variability due to a persons body, phone orientation, obstructions, > > > transponder location relative to cell phone, ... all have to be taken > > > into consideration to make a useful product. > > > > One potentially useful scenario might be: > > > > Instructions for using compass. > > > > "Walk in a straight line in the direction the top of the cell phone is > > > pointing; choose a target to walk toward and hold the cell phone flat > > > like you would any mechanical compass. The cell phone will beep when > > > you arrive at the calibration position." > > > > "After hearing the beep, rotate about your position smoothly and > > > slowly (4 seconds, 1 second and 1 beep for each 90 degrees), until you > > > return to face your starting position. The display will automatically > > > display the compass bearing around this position." > > > > "If you move more than 15 feet from this position, the compass bearing > > > will be removed from the display until Calibration is done for a new > > > position. This prevents the user from using old data." > > > > This would be done every time a person wanted a compass bearing. > > > > At this one position, they could rotate back and forth and get compass > > > bearing information. When the GPS sensed any new position, the > > > Compass would replace the compass readout with "Perform Calibration". > > > > They would have to repeat calibration every time they wanted a compass > > > bearing unless higher level algorithms are running in the background > > > while the user is walking. Updating lookup table(s) with information > > > to derive similar data from moment to moment. > > > > Again, this scenario is only useful if a compass sensor is not > > > available in the cell phone. Which is almost all cell phones made > > > today. > > > > But I agree, if a compound MEMS chip (with Mag sensor) were > > > incorporated in cell phones then this sensor fusion option would be > > > unnecessary. > > > > James > > > > On May 19, 5:33 am, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > > > > > Hi James, > > > > > This is helpful. Thank you. It is good to know someone is thinking > > > > about this. After reading the IEEE abstract, a little clarification on > > > > use is always helpful. > > > > > Our applications are eyes free, because the phone should not be > > > > competing for those revenue generating resources. So use will happen > > > > with the phone stored on the person’s body, say, in a shirt pocket, > > > > held to the person's ear, or on their belt. The compass needs to work > > > > no matter how the phone is oriented. The IEEE abstract seemed unclear > > > > on how it would work in a handheld device. It would be great for cars, > > > > though. With the two accelerometers, there is a calibration routine > > > > where a person wears the phone normally and walks in one direction. 10 > > > > ft should be enough to get enough calibration to be useful. It can > > > > recalibrate in the background and alarm or adjust ... > > > > > Sensor Fusion is a new word for me. Differential sensors of finite > > > > resolution have been around for a long time. Consider the roach, or > > > > any bug with antennae. They sample air at distant points allowing the > > > > organism to select a direction. The longer the antennae, the smaller > > > > the gradient the organism can detect with sensors of a fixed > > > > resolution. Long antennae help folks figure out what is going on. > > > > Sampling acceleration at distant points is going to give you better > > > > information on angular velocity and acceleration (how fast you are > > > > spinning) than using a single sensor in the same way. > > > > > Thank you for pointing out that radio field interaction can provide > > > > information... since a human body can influence that, it is probably > > > > good to not rely on that method. Two sensors a fixed distance apart > > > > should require little attention and provide good results across many > > > > devices once it is engineered. > > > > > My job is to show why it is worthwhile to spend that dollar for > > > > pedestrians who don’t read maps. Android has the tools to do that, > > > > even in today’s SDK. > > > > > On May 18, 7:48 am, James <[EMAIL PROTECTED]> wrote: > > > > > > A MEMS chip can be a collection of sensors (temperature, accelerometer > > > > > (x,y,z), atmospheric pressure, Hall effect sensor (compass), ...) all > > > > > built into the same chip. In mass production the chip could be > > > > > relatively inexpensive. > > > > > >http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/20/35967/017046.... > > > > > > However, an Android shortcut would be to use the GPS sensor and your > > > > > relative direction of travel to produce a compass bearing over 100 > > > > > feet of uniform travel. For each model of cell phone the antenna > > > > > sensitivity changes as you rotate the cell phone about a point. This > > > > > could potentially be tied in with relative position movement to > > > > > estimate a compass bearing about a point. > > > > > > But as I said, the lookup table would be different for each model of > > > > > cell phone. > > > > > > This type of engineering where you take two sensors with low > > > > > resolution to combine their results to provide greater resolution is > > > > > called "Sensor Fusion". > > > > > > Basically a cell phone antenna signal does NOT have the same signal > > > > > profile when you rotate left versus rotate right. This can be > > > > > capitalized upon to determine the relative bearing of which the > > > > > compass is facing. Coupled with the cell phone GPS the relative > > > > > bearing can be referenced to the true bearing. A lookup table can > > > > > provide a correction factor and thereby produce Magnetic Bearing; vis > > > > > vi Compass. > > > > > > James Dunn > > > > > Table of Contents - Similar Insights related to technology > > > > > applicationshttp://blog.360.yahoo.com/jamesbdunn?p=207 > > > > > > On May 15, 9:23 pm, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > > > > > > > I have no idea how much a cell phone with a compass costs. I don't > > > > > > see > > > > > > why it would be expensive if there were enough of a market to micro > > > > > > machine it like all those tiny mirrors. > Who knows these answers? > > > > > > > Thanks, > > > > > > Ed- Hide quoted text - > > > > > > - Show quoted text -- Hide quoted text - > > > > > - > > ... > > read more »- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Discuss" group. 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