Decided to timelapse everything until the grand finale. Ran down with the guerilla pod, which was useless for video. At least the traffic was better than driving down with the video tripod. Being many years since the last manually exposed fireworks video, forgot everything.
1/30 F/2.8 ISO 1600 was a decent exposure. Stopping down would have sharpened the dots, but added noise. Desperately needed a video of a past show to know where to point the camera, but Sprint was completely down. Had to reposition during the show. 15mm with 1.6x cropping was just wide enough to get everything.
Audio was at the lowest setting. Clapping produced a decent approximation of the maximum loudness. Should have used a simple pair of outboard electret condensers, at minimum. Anything would have had better stereo separation than the Canon's microphone. Amazingly, it still managed to differentiate the guy on the right.
Now, they're doing it at slightly closer ranges, with modern wide angle, stabilized cameras. It has always depended on a very accurate attitude estimation with GPS coordinate triangulation.
The athlete still looks like a tiny dot. The newest videos are a lot more edited for when the athlete goes out of frame. It has the feel of trying to get a lot more mileage out of the same old capability.
Getting a closeup is really hard. The easiest way is to have a very long lens camera with many levels of stabilization & chroma key detection of the athlete. The last of the Sony Handycams had excellent stabilization. So far, they're all marketing gopro cameras, so this method is not being demonstrated any time soon.
The HDR-PJ540 is the current optically stabilized one. It's quite large & expensive. Stabilization on that level is now a novelty feature, since no-one cares. It's a huge investment, just for the follow me mode.
Another way is to fly up close. The advantage is a much easier time initializing it, much smaller vehicle, getting the athlete started in frame, & ability to fly in confined spaces.
GPS is no good. The athlete has to be the navigation reference. Time of flight cameras & structured light cameras don't work in daylight. The movie camera alone can resolve position, within strict limits. It would take having the athlete wear multiple chroma key markers & having 2 markers in frame at all time. The markers either have to be a constant distance apart or they need a way to tell how far apart they are, maybe by some electromagnetic sensor which has been demonstrated. Single camera autopilots have been done before.
It still would need GPS at long range. Any method using chroma keying without a GPS aid is going to be prone to false positives & flying away.
The most amusing part is that biology majors still make the least, even when they work in engineering. Coworkers who studied physics did indeed have a much easier time getting jobs. The study probably only looked at people working in engineering.
After taxes, the highest bracket only makes $1.5 million in his lifetime. The average house in a dot com area is $2 million.
The author made a big deal about eliminating selection bias, basically people getting engineering degrees because they're smarter in the 1st place. Wish studies that showed married women live longer than single women would correct for selection bias. Men pick women in better health. Marriage has the opposite effect on men's health.
So the blog is moving to Bakersfield because Tampa is completely unaffordable. The out of state tuition alone is bleak. The rent is equivalent to Silicon Valley, 10 years ago. Bakersfield has the same temperature as Death Valley, but the heat index is the same as Tampa. Who knew all those tourist attractions in Fl*rida had the same heat index as death valley.
Decided to kick it up to 15V with fixed commutation mode & it actually exceeded the required speed at 8.5mph. It sucked 2.8A to start & 1.9A to run. Keeping it going straight during the start was a problem. After commutation begins, it's quite stable. The commutation was much slower than the optimum speed, but required to get enough torque. The coils got too hot.
Some more debugging & speed regulation could slightly reduce the current. The idea is to use back EMF, but add a certain delay so the voltage is regulating speed, yet it's less sensitive to stalling. This has been tried before, without success. Its range on 4S 900mAh would probably be 20 min or equivalent to the brushless Losi micro T on 2S 200mAh.
Another idea would be to measure the back EMF time. If it was too far ahead of commutation, reduce the voltage in the next phase according to a PID controller. If it was too far behind, increase the voltage in the next phase. That would give better torque, but not slow down on hills. Normal rovers use flywheels or slip clutches to avoid stalling.
The time for this has probably run out. There probably is a future in direct drive brushless rovers. They offer a way to get a wide range of speeds or more biomorphic movement. A direct drive robot can slowly rotate to scan a scene, then dart forward. A conventional robot is geared to go either extremely slowly or extremely fast.
So the VIIRS was built in LA. There's no data on how it works, whether it's based on a large aperture or an extremely radiation hardened DSLR sensor. It's sensitive enough to detect a flashlight in the ocean. Connoisseurs of its data have noticed a large patch of lights in N Dakota which didn't exist 15 years ago.
It was worth documenting the last bit of data from the back EMF motor control fiasco. It begins with the full power applied.
Oscilloscope plots of the full power voltage are never shown, but they have the clearest view of the 2 powered phases with the back EMF clearly visible in the floating phase. There's a glitch where it goes from 9V to floating. Software detects the halfway point to determine the commutation time.
The normal oscilloscope plot shows PWM modulated voltages. The back EMF phase is less visible. The writers for EETimes tend to be more interested in showing they fully understand the concept personally, with the most obtuse diagrams, rather than conveying it to someone else.
While it's nowhere close to a comprehensive solution, it does the absolute minimum of superimposing field of view for a given focal length on a satellite photo. No more packing anything but the exact lens you need.
It's hard coded for a 35mm DSLR of a certain crop factor, horizontally mounted. The next step would be either a vertical mount option or direct entry of the sensor width. Height of the field of view can't be easily conveyed. The oblique satellite photo gives a rough estimation of the height of an object, relative to the field of view. A street view overlay could be more useful, but their imagery is limited to just public roads.
Field of view gets less accurate as the lens gets wider. It probably doesn't represent a fisheye lens at all.
Undoubtedly Switchbox was a lot cheaper than the $3 billion Google paid for Nest.
The Digital Diet Staying In Shape With Your Computer
Not to be confused with the billions pouring into wearable fitness tracker startups.
Then there's everyone's favorite
Travelshopper lets you scan flight availabilities (on virtually any airline worldwide), find airfare bargains...
Except for the names, it's the same story.
To be sure, we live manely the same way we did 30 years ago. It can be depressing to see the same problems being solved then that you're solving today, but that applies to everyone. Every profession still does manely the same thing it did 30 years ago, whether in technology or anything else.
The 1 thing that sort of feels new is the drone. It absolutely didn't exist in anyone's mind until 2007, but energy storage continues to keep it out of the realm of practical problems like the Digital Diet. Aerospace is intriguing in that space missions are much cheaper, yet there are far less of them.
Doctors, lawyers, & teachers solve exactly the same problems they did 100 years ago, despite minor changes to their tools. These are not professions for you if reading about your same task being done 30 years ago is depressing. Most people aren't this way about the past, but some do need to solve new problems.
A motor is tested for a winding error by using the right hand rule, a fixed current source, & permanent magnet. 10 & 3 were swapped.
The balancer was officially recycled after an attempt to make it balance. There was a lot more involved than expected. Mass distribution made a difference. Less mass was better. It couldn't balance with a battery anywhere on it. An outer loop needed to calculate a target angle based on the number of motor steps. An inner loop needed to hit the target angle by giving motor steps. It didn't seem to have enough traction on the carpet. There seemed to be a maximum limit on the feedback rate.
So Virgin sent out a hidden update which disabled the wifi tethering again. It also disabled bluetooth networking. Merely changing phone numbers caused it to download the update. The update didn't affect the Android core.
For many years, people networked using bluetooth + ppp. They opened a serial console over bluetooth which required some AT commands to get the console to go into PPP mode. Then Android introduced PPP over ADB. Then a new standard for networking over bluetooth appeared called PAN.
Now some random notes for PAN.
# enable bluetooth dongle on the laptop
hciconfig hci0 up
# A menu option is required to allow the phone to be discovered by the laptop
# Connect the phone to a /dev/rfcomm node
rfcomm bind 0 BC:F5:AC:2B:34:96
rfcomm show 0
# test connection
# Allow the PC to be discovered by the phone
hciconfig hci0 piscan
# Show status of PC
# allow phone to pair
# change class to networking device
Class = 0x020100
# restart bluetoothd
Due to its extremely remote location, the Goog couldn't find any decent photos of the teardown. It's 3.5 miles from the nearest parking lot. Decided to try to bring it to the viewers at home, like they never saw it before.
The infamous pier was reinforced before separating the mane span. In the old days, it took a complicated shock absorber like this to absorb the pushing of an earthquake. The road would collapse. If someone died, so be it. The shock absorber would rip apart if the pushing force from the mane span was replaced by a pulling force.
Self balancing motorcycles have been promised forever. Self balancing is the key to any robotic motorcycle. Some tried reaction wheels. Some tried legs to push themselves back up after falling over. http://litmotors.com/c1/ has been working on one since 2012 & recently bought a lot of advertizing.
There's 1 drawing of 2 control moment gyros. They claim thousands of ft-lbs of torque. The videos are carefully designed to have forces pushing at very low points, for short periods of time, to minimize the angular momentum & not saturate the gyros. No turns are shown. It needs a fancy turning algorithm to desaturate the gyros.
It needs to deploy its automatic kick stands or ask the driver to stick a foot out, if it's stationary for too long. It hardly seems worth the complexity & mass, just so the driver can be protected from the weather.
It was time to recycle the G-buggy. After 109 miles, with no replacement parts, nothing on it was considered useful.
It left behind a decent drive system with high torque & very little gear reduction. The torque was much higher than any replacement, making the replacements seem unlikely to work.
Very beefy motor with lots of power factor correction. They still have to invest in efficiency, even on the cheapest toys. Someone must have sat down with a voltmeter & current meter, connected various capacitors & inductors until the phases lined up.
A new plan was the simplest possible brushed motor wheeled thing. It would passively balance when stationary, allowing it to turn. It would rest on a 3rd wheel when moving, limiting it to very slow turns. A 4th wheel or springy thing would be provided, to keep it from flipping over.
After some time, discovered the spare EM812's are not real MOSFET motor drivers, but the cheapest won hung low BJT bridges. The G-buggy's controller was still impossible to beat, as a simple motor driver.
Some geared brushed motors didn't have nearly as much starting torque as the direct drive brushless motors. Brushed motors were the simplest, lowest voltage solution.
There's real appeal in a passively stable, brushless direct drive solution, from the standpoint of efficiency, but it requires a lot of software magic to get enough starting torque, then transition to back EMF mode for optimum efficiency. The startup is still terribly inefficient. Sensored motors are apparently the recommended solution for a wheeled vehicle.
The passively stable brushless direct drive solution would use up all the parts that could make a balancing robot. A balancing robot that balanced when stationary, then used a 3rd wheel for speed is still tantalizing. There's another idea of a balancing robot that used a control moment gyro for stability at high speed. It needs just enough inertia to dampen the forward flip, but can stabilize itself with its 2 wheels, unlike the reaction wheel unicycles. That...Continue Reading
The old G-buggy officially died after 109 miles. A wheel axle bent when it was stepped on. More predictable steering might have prevented the human collision.
Another part of its frame had long been cracked. It's hard to think of another pacing mechanism besides the treadmill. The recent focus of investors has been heartrate monitors, but these are not realtime.
The decision was made to go for full functionality without ESC mode, using a table of power vs speed, if at all. It doesn't look like a balancer is going to hit the required speed, even with a modern 1khz IMU & direct drive motors. With 900Mah batteries in stepper mode, the range would be 4 miles.
Getting over curbs would be an ordeal. The problem is a stopping force on the wheels causes it to flip forward. It needs a sudden boost in power to get the wheels in front of its center of gravity again. Most balancers use gear motors with a low maximum speed, to get good stationary power, but the steppers would still be near their maximum speed at 7.5mph.
The segway can go 12mph, for $2000. Nbot was still the most fully documented, seemed the fastest, but was far too slow. It demonstrated the front flipping problem nicely. There was a video of a really slow one in a balancing robot race.
So the last interview was the standard bit packing problem from many interviews before & that was the entirety of their dialog. They want you to pack a certain number of bits from each byte of an array into another array.
The traditional way of implementing it as fast as possible for an interview was to create a temp array of 1 byte per bit, write the packed data to the temp array, convert the temp array from bytes to bits. The way real compressors do it is to spend the time to make a write_bit function that writes a single bit at a time to the output array, maintaining the required state variables for the destination bit between calls, & padding the final byte with 0's. Suspect they want the latter.
Rather than spend the time verifying it alone, figured he had a test data set which would quickly show if it worked. That revealed a function argument was implemented for the number of bits to keep, but he wanted it for the number of bits to remove. Reversed the variable & it worked, but this ended the interview.
Out of a pool of many thousands of applicants, some would have had recent memory of data compressors with the write_bit method, some would have nailed it on the 1st try, some would have verified it on their own, appearing to nail it on the 1st try, some would have copied the solution from past interviews, some would have had snazzier solutions. The winner is purely random, but good enough. It may be they already had someone else picked, but had to follow through on the interview process for immigration laws.
Peers say they're "just hanging on" & the democrat controlled news media isn't covering reality. Reviewing what some of them did over the last 15 years made the MS seem a lot more important.
A quick test revealed the 50 turn motors could reach the required 8mph with the required torque, at 15V 0.6A. They probably need active cooling & stall detection. It comes to 15V 1.2A for the motors, 6V 0.25A for the cooling fans, 3.3V 0.06A for the CPU. It would take 2Ah, 15V which is too heavy with modern batteries.
It's more efficient to reach that speed in ESC mode than stepper mode, but transitioning from stepper mode to ESC mode would require a super algorithm. It needs to power all 3 phases & adjust phase for stationary balancing, then when RPM reaches a certain point, powers just 2 phases & adjusts voltage for balancing.
The balancing robot needs an outer loop further regulating speed by tilt angle. If the inner loop voltage is too high, it tilts less. If it's too low, it tilts more. If it's stationary, it needs to tilt based on the amount of phase change.
Such an algorithm would have earned a master's degree, 15 years ago. Amusingly, a commenter on a goo tube video about the nbot balancing robot wrote "When you get that awkward [interview] question 'so what skills do you have for us', slap that robot on the table and you can name you salery. After all, how many people do you know who can make one of these from scatch?" 5 years ago. Times have changed so much, jobs have become so much more specialized, & robots have become so much more commoditized, such a thing won't get any more than a teary eyed "My kid got 5 for XMas. Moving on..."