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Jack Crossfire's blog
Posted by Jack Crossfire | Jun 08, 2014 @ 05:14 PM | 1,873 Views

The compressor proved essential over the last 15 years, but with a proper Lipo, it's so much more convenient. No more draining the car battery, opening different car doors, shuffling the cable, leaving the key in the ignition to power it. Very old cars require keys to be in a slot & don't automatically inflate their tires, but they don't have the mandated GPS tracking, remote engine cutoff, & tax premiums the government now requires.
Posted by Jack Crossfire | Jun 07, 2014 @ 04:23 PM | 2,659 Views

Despite all fears of shoemageddon, the 1st RC car run with the new shoes happened with no issues. It was a bit easier, thanks to 2 easy days. Didn't feel any hunger, thanks to a large salad with nothing else. The shoes just felt heavy. Fully intact soles put them at 11.6oz. After wearing down, they were 10oz.

At 7.4V, GPS reported the fastest segment was 8m8s per mile for 1.8 miles. The same segment uphill was 8m31s per mile. After GPS reported 10.25 miles, the battery started fading fast. Automatic steering died completely. It now has 109 miles on it. Used gyro * 4 for the automated steering, to no avail.

Still expect the tires to go before the motor. It's going to suck to spend $44 on another piece of junk instead of an ideal solution.
Posted by Jack Crossfire | Jun 06, 2014 @ 04:30 PM | 2,140 Views
SpaceX Landing Restoration 2014/06/04 20:52:32 GMT (0 min 21 sec)



Reading about how the restoration of that video was done, it's amazing how many people are able to hand restore a corrupted H.264 video stream, fixing the corrupted headers in a hex editor, writing a custom macroblock editor to fix the macroblock encodings in every single frame.

Years ago, it was a small miracle just for someone to know what a GOP was, let alone fix the macroblock encodings. Overnight, that skill became normal. From their piano competitions, to their self driving cars, to their H.264 video repairs, the millenials are a new league of talent, far more than generation Y & a different universe than generation X. It explains why job interviews are so much harder than 5 years ago & feel a lot more like standing on your head.

Fixing the SpaceX video was an exceptional case that required experts in H.264 macro block encoding editor writing. Attacking exceptional cases that require standing on your head is almost entirely what feeds the new economy.

It was the 1st time a 1st stage ever landed itself. It was an idea proposed only in drawings, for almost a century. They only launch 3 times per year, with 1 launch capable of having enough margin to attempt a recovery. The powered descent is too expensive to make more than 33% of their launchers recoverable. To be 100% recoverable, they would have to move the remaneing 2 launches per year to Falcon 9 heavy, which would be completely unaffordable.
Posted by Jack Crossfire | Jun 05, 2014 @ 09:27 PM | 2,269 Views

Now some interesting nuggets about the reprinted satellite photos which 1st appeared on May 25, 2011 from http://www.benedictredgrove.com/aeronautical/01.

...Continue Reading
Posted by Jack Crossfire | Jun 05, 2014 @ 12:22 AM | 2,042 Views
Should have tested the motor speed before anything else, because.

Max rpm: 823
diameter: 60mm

Crunching the numbers revealed a maximum speed of 5.78 miles per hour on 7.4V, with no load. Torque decreased as speed increased. That design was busted. The L6234 motor chip required 7V, busting any single cell ideas, too.

12V got it to 1310RPM or 9mph with no load.

The stock winding had the required torque & RPM, but took 3A when stationary, decreasing to 1.3A at its top speed.

The 130 turn DT700 hit 527 RPM at 12V 0.13A with no load.

A balancing robot with the required speed would need gearboxes. The direct drive idea with rewound motors would make an excellent hobbyist robot, but not meet the required application.
Posted by Jack Crossfire | Jun 03, 2014 @ 11:50 PM | 1,990 Views

Well, it definitely looks like an exact copy of the millions of other balancing robots. The problem is they all need a minimum height to have enough inertia to stay upright. Some use ballast. Some use 2 phase stepper motors. None use 3 phase brushless motors. They all use obsolete, heavy electronics. Interest in balancing robots vanished after 2007.

Many use 2 inline wheels & a large reaction wheel for horizontal balance. There are some which use a single fat wheel & no reaction wheel but probably can't turn. Many are unicycles with a large reaction wheel for horizontal balance. A control moment gyro can also be used. All of these are more cumbersome than 2 side by side wheels.

Weight shift can't balance a stationary unicycle. The problem is the astronaut problem. It needs an external force to act on it, to stay horizontally upright.

Performance of 2 wheel robots on trails is probably bad. Dirt getting in the motors is a big deal.

The balancing robot is extremely light, for what it is. A brushless gimbal sacrificed its brain & some aluminum for it. There's a huge bonus if it can run on 3.7V. So you need to find the minimum power with the recycled 7.4V board & spin a new board which can run on 3.7V if it works.

Posted by Jack Crossfire | Jun 03, 2014 @ 01:56 AM | 1,925 Views

Reviewing spare parts that could make a balancing robot, there are some 8:1 gearboxes, but no suitable motors. No way to attach a bell motor to them. There are some foam wheels, which wouldn't last long. They attach directly to some bell motors, which need 1.5A, but still probably wouldn't produce enough torque. No way the shaft would be straight enough for the gears to mesh.

Direct drive brushless motors are the cheapest way to get a balancing robot. They need to go from very fine adjustments to 1132rpm. The voltage would be low for stationary balancing. It would go to maximum for all movement. Brushless motors would not automatically change speed based on grade. Current is constant for all loads. The timing of the back EMF has to be sensed to detect the load & manually adjust the speed. There is an algortihm on http://edn.com/design/analog/4368829...er-motor-stall

There are some pancake motors which have a tiny bit of clearance but probably enough torque. They either need skids for protection from rocks or slightly bigger wheels. The bearings probably wouldn't last long with a solid wheel. The days of cheap solutions are over.

The ideal motor is the bell motor.

A session of pin punching, allen wrench punching, back & forth sliding, & metal removal liberated the shaft. It was heavily jammed in.

...Continue Reading
Posted by Jack Crossfire | Jun 01, 2014 @ 04:38 PM | 2,078 Views

First build a product, then get a customer, then get friends-and-family money (or money from revenues which is cheapest of all) and then think about raising money. But only then. Don’t be an amateur.

But you already knew that.

Trying to get Mark Cuban to invest because “this would be great for the Dallas Mavericks.”

Never happened. We solicited the Reno homebuilder, the Canadian premier, & the Singaporean billionaire, but never Mark Cuban.

I just started my business. What should I do?
Sell it as fast as possible

Something workers should keep in mind. Advancements in 3D printer technology briefly swung towards hobbyists when the Makerbot came out. After Bre Pettis sold his business to Stratasys for $1 billion, they continued to make Makerbots, but innovation once again returned to just the high end with a clear division between what would be consumer & what would be professional. Maybe it set hobbyists back 5 years, but Bre did the right thing in selling as fast as possible.

Watching amateurs fail is not pretty. Denial of reality gets wider & wider. Egos get bruised. They all eventually asked for free work because just 1 more demo would seal the deal or they were going to have money next week. If 15 years of demos couldn't seal the deal, 1 more wasn't going to do it & they never had money next week. It was better to stop working & bruise their egos than use your bank account to dig them a deeper debt hole.
Posted by Jack Crossfire | May 31, 2014 @ 08:03 PM | 2,371 Views

Night run with the RC car. The slowest of any previous RC car run, yet it felt like maximum speed. Even had the most stops of any previous run, to fix steering crashes. The temperature was only 54F. Most likely a combination of diet & intervals the day before. The salads aren't putting out. Interval training used to require a lot more recovery time.

Installed headlights, which aided steering & visibility. No need for a headlamp. Steering was still bad, but can't improve anymore without a new vehicle. With the voltage at 7.3V, the fastest downhill part was 8m14s per mile for 1.8 miles. The same segment was 8m38s uphill. The battery seemed to have over 10.5 miles in it, despite 0.06A going to the LEDs, because of the slower speed. The gyro failed to initialize, so walked home & reflashed it with no gyro limit before the run. Total mileage is 99.2.

While pounding the pavement, the RC car idea started to seem pointless. The problem is there are electronic ways of pacing, which don't require steering. Google glass can overlay a virtual pacing object on the scene. Phones can read out the pace. These methods are not as realtime, not as precise, & aren't as tied to the real world. A previous attempt to have GPS derived pace read out every second was not accurate enough. Augmented reality overlays are really bad.

The car was more motivating, conveyed the exact pace in realtime, & could carry supplies or a camera to record the journey. Electronic pacing is still required for a race. Apparently, the sensor of choice is a footpod that measures g forces in 3 dimensions, in addition to number of strides. The trick is conveying the information to the user in realtime. Perhaps the metronome can change sounds or the phone can read out motivational sound clips. It's hard to beat a physical object.
Posted by Jack Crossfire | May 30, 2014 @ 05:22 PM | 2,187 Views
Posted by Jack Crossfire | May 29, 2014 @ 07:37 PM | 2,329 Views

An idea proposed on the Jack Crossfire blog finally hit the big time: synthesizing humans on other planets instead of transporting them. The 1 lone blog reader needs to look up that nugget & PM the link. It wasn't 3D printing specifically, because no-one made any money on 3D printing in those days, but it was beaming the information contained in a human to a machine on another planet that could synthesize a replica of the human, consciousness & all. The idea has been around forever, but this was the most prominent person to quote it.

For better or worse, an idea still needs gatekeepers to become official. Now if only Neil Degrasse would quote it.
Posted by Jack Crossfire | May 28, 2014 @ 07:40 PM | 1,561 Views
There's little more to improve in the functionality of RC car exercise coaches. Variable throttle would be nice, but not as ergonomic. A 2 wheeled balancing version would have better steering, but not enough to justify the cost.

The next win is autonomous path following. If the car follows behind the athlete, it's easy. If it's in front, it's a lot more than slightly harder. 1 rule can be to always keep the athlete centered in a rear camera. That lets the human control what side of the path it's on, but which path?

GPS is too inaccurate to follow a preprogrammed path. A compass is too inaccurate to follow a preprogrammed heading. Pole cams, lidar, chroma keying, are all too big or expensive.

Combining the compass idea with the rear camera might actually work. The key is the distance between car & athlete is relatively small. Any deviation from the intended path makes it steer away from the intended angle to keep the athlete centered. It makes an angle change big enough for an erroneous compass to detect.

It would be smarter, detecting when the athlete was off center, calculating what turn is required to center the athlete while not deviating from the desired heading. The heading would be determined by waypoints, but instead of current position to waypoint, it would be waypoint to waypoint. It would need GPS & a buffer factor to determine when a waypoint was satisfied.

The athlete would have to be a certain distance behind. It's very hard...Continue Reading
Posted by Jack Crossfire | May 27, 2014 @ 11:23 PM | 2,128 Views

Doubled the amount of aluminum between the LM317's & the board. Ran 3 laps around the complex, giving a rough estimate of the speed. 7.5V was now well above what the human can sustain.


At 7.2V, it was


Tested 7.3V last. It was


It was definitely inconsistent. GPS seemed accurate enough. The Lipo may be at the end of its life.

The I feedback made a small improvement in the steering. It still occasionally veered off course, but it managed to correct after a certain time. It's probably the best compromise between going crazy & not steering at all.

Finally moved it to C. Random failures abounded. Computing power went way down, manely owing to the required stack size. SDCC ended up not initializing the stack pointer. The stack pointer was 1 of the few registers the PIC didn't initialize. Manually put it at a reasonable address. There were probably also stack overflows. Managed to get the variables as compressed as possible, overwriting the gyro initialization variables. It didn't have any more issues. It ran fine at 3.3V, despite being rated for 5V.

SDNM doesn't work, making for a lot of guessing for the stack size. The free, 10 year old, through hole 18f1320's have probably made their last project. There are 2 more 5V ones, 1 more 3.3V, as probably dedicated spares. The 18f1220's are all gone. There are some exotic ones: 3 x 18F4685, 3 x 18f6585, 3 x dsPIC33fj128mc802, a lot of 18f458's intended for crash damage.
Posted by Jack Crossfire | May 27, 2014 @ 02:47 AM | 1,586 Views

Another day banging on the GPS analysis software yielded an easier way to get interval training times, manely basing pace on a fixed distance into the past instead of fixed time. The calculation was more complex. The result was no more accurate than fixing time, but easier to read.


The interval training app turned out to not work unless GPS was in keep on mode. If it's closed & reopened, it can't restart the alarm. What would be nice is if Android had a provision for detecting if an alarm is already set, so the alarm can be set wherever there's a chance it may need it.
Posted by Jack Crossfire | May 23, 2014 @ 01:34 AM | 2,634 Views
Since Google's interviewing formula became accepted as the proven way to hire everyone, algorithm tests on codility.com have all but replaced the interview. The 1st codility test was 15 minutes for 2 problems & a total failure. Assumed it would be equivalent to programming tests in the past, but it was drastically harder, with a much clunkier interface. Thus ended any chance of ever working at Airware.

They might have actually configured it wrong, because the guy said it would be 70 minutes. The 2nd codility test felt better, but also had 60 minutes for 2 problems. There is never as much time as a real job. The trick to winning in Google's world is more about mastering the algorithm tests than being good at the job.

For codility, you have to read the instructions in the sample tests, take the sample tests or at least formulate how you would solve them, then read as many blog posts about the solutions as possible. They require passing the complexity requirement, passing all corner cases, handling the very large numbers in their entire stated range, very small numbers, very large data sets, & very small data sets. Their example data sets don't test the corner cases. Cleanliness of code doesn't matter & there isn't enough time to clean it up, anyway. Sometimes a clue is given in the problem, like the range of a variable being the size of an array, thus you should make a lookup table, or order sqrt N complexity, thus a for loop of sqrt N...Continue Reading
Posted by Jack Crossfire | May 21, 2014 @ 11:14 PM | 2,447 Views

In another 10 miles of driving, the voltage regulator rework definitely reduced the amount of power. The fastest mile today was 8m2s. Things dragged on at 8m30s per mile for most of it. The recommended pace for a tempo run is 8m22s. Staying close to the car made it easier. Had nothing but salad before it. The fiber seemed to prevent crashing. Tried the most aggressive sugar content in the recovery drink.

Steering with AUTO_STEERING_PERIOD reduced all the way to STEERING_PERIOD / 4 was very ineffective. After 86.2 miles, the steering mechanism has deteriorated to the point of requiring I feedback.

For a good time, the GPS log can now be analyzed online.

Posted by Jack Crossfire | May 20, 2014 @ 04:20 AM | 1,945 Views

There is going to be a quad copter/drone delivery service, but not what you think. It would be impossible for a quad to fly from the distribution center to a house, with current technology. What is going to happen is a truck dispatching a quad the last 50 ft to deliver to a front door or some kind of target the customer prints out on an 8.5x11" sheet of paper & sticks to the door.

Current technology is good enough to just barely make it more efficient for a very highly maneuverable flying robot to do it than to have the driver get out of the truck. It would require another robot in the truck to load the copter. The navigation sensor of choice would be Vicon on the truck guiding it to a landing site within visibility of the street.

It would require another layer of route planning beyond the current street algorithm. It would need a database of every floorplan or lidar on the truck to do final route planning to the door. As unlikely as it is, the same thing happened to garbage men riding on the backs of trucks. That became automated, decades ago.

The ultimate plan of flying from the distribution center would need something much more reliable & bigger. A current, gas powered copter could probably do it at great expense & with a few crashes. It would fly above the destination & dispatch a smaller copter the last 50 ft. The problem is going to be solved, but it's hard enough to ensure a few years of job security.
Posted by Jack Crossfire | May 17, 2014 @ 03:55 PM | 17,119 Views
Netscape Navigator 7.2 (5 min 17 sec)

Things were so different, in those days. The Netscape server room had about as much computing power as a modern phone & far less bandwidth. The PC was king. Jobs were for life.

The big ass PC application was king. Thousands of menus had to be literally driven by the user. Everything a developer wrote was visible. Nowadays, it's all hidden & automated. There are maybe 2 menus.

The Facebook app has virtually no user interface, but 54 services in the background. Each service has probably 50 developers. All of its functionality is automated. The Google Play app has 22 services, but virtually no user interface. All the stuff that would have taken a user going to a menu in 1999 now only becomes apparent in the rare case a service can't figure out what to do & pops up a notification.

It doesn't feel very individualized, in a world where what everyone writes & thinks is now determined by an algorithm.
Posted by Jack Crossfire | May 16, 2014 @ 02:30 AM | 2,127 Views

When used carefully, it doesn't show annoying animations, popups or make you wait for additional bits to load, when you scroll down the page.

Accessing it through jquery has been required for any kind of day job, since 2011. jQuery adds around 300kb to every page load & is another layer of indirection, explaining why web apps are so slow. It theoretically reduces the amount of porting between browsers, but trying the various jquery demos showed similar browser incompatibilities to pure javascript.

Javascript behaves so differently on each browser, it's not really portable. There is a subset of math functions which seems to be portable. The DOM trees are vastly different. Chrome seems to have the most bits working.

It's very slow for analyzing just 32000 data points & the user interface is always going to be clunky, no matter how much tweaking you put in. It's a practical way to analyze small sets of data, when polish doesn't matter.

After much refinement, a GPS analysis tool emerges. It does everything you need, but no-one else ever implemented. It mostly works on any platform, with no need for installation, libraries, compilation, or waiting.

Then, the reality of why we have a cloud & all the investment money in cloud startups emerges. 1st, it has to be called cloud instead of web to avoid another .com collapse. 2nd, getting the data from a phone to the web app is a real pain. The PC...Continue Reading
Posted by Jack Crossfire | May 14, 2014 @ 09:52 PM | 2,956 Views
The RC car empty & 7.5V did 8 minutes on the fastest downhill & 8m24 on the uphill. It had increasing numbers of steering glitches. Didn't completely discharge the battery or survive the full 10 miles, this time. These RC car runs are intended to go until the human drops, rather than battery depletion. The temperature was 80F at starting time & 77F at finishing time, with a strong north wind. The Danville run was 50F with no wind. This route had fewer stops than the Danville route.

That brought it to 76.2 miles & its 1st broken TO220.

The rebuild was the crustiest circuit ever. Dave Jones would have a fit. All that weight to avoid paying up. Not sure how we ended up in a world where the only BEC with fully adjustable voltage is from Castle Creations & requires a proprietary protocol which no-one ever bothered to reverse engineer.

Fully built buck converters with the required parameters are rare things. It might be a very unique application to want constant output power, variable speed, making the car slow down on hills.