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Archive for April, 2016
Posted by Jack Crossfire | Apr 30, 2016 @ 06:10 PM | 9,034 Views
Future of Faster | The PUMA BeatBot (1 min 30 sec)


It only took 3 years, but MIT & NASA finally caught up with the blog. Their version of the pacing robot uses line following for navigation & they didn't seem to have solved the manual control problem, yet. The line following is based on IR leds with a video camera so it only works at night, on a track.

It won't be long until they discover line following is not worth as much as an ergonomic manual control.
Posted by Jack Crossfire | Apr 27, 2016 @ 12:43 PM | 8,421 Views
After 2 weeks of round the clock commuting & moving, the home network came up again. It was sheer brilliance for Comca$t to make every one of their rental modems a public hotspot & it's amazing AT&T never copied the idea. When the idea 1st came out, the internet screamed bloody murder. What would be the impact on performance for subscribers when their rented modem was shared with a user on a different account? Of course, it was more AT&T screaming bloody murder & the internet just doing what it was told.

In the fullness of time, the outcries disappeared like any dead celebrity meme & the sheer brilliance of the move arose. Despite the insane cost, most people still rent modems instead of buying their own for half the price. Every one of those millions of modems automatically pops up on every wifi enabled gadget, a gigantic window saying "XFinity". It's the biggest customer sponsored advertising blitz, ever.

It takes very forward thinking to get to an advertising blitz this extreme. It began when the wifi standards were ratified. Someone had to realize allowing a router to push a web page for logging in was a useful feature. The true power was in the standards process.

So when finally subscribing to Comca$t, after years of endless XFinity popups on every wifi device, the hotspots instantly worked. There was no need to buy a modem at all or wait for an installation kit in the mail. You could just use your neighbor's wifi & it even went up to 8 megabits. Not sure if the speed was throttled based on the account. Every modem automatically signed in.

When the wired modem finally arrived, it required jumping through an activation hoop. After this, the wifi hotspots no longer worked. It seems they only allow use of the hotspots before activating your modem. Then, they require upgrading your plan, yet another marketing move based on human fear of denial.
Posted by Jack Crossfire | Apr 22, 2016 @ 05:25 PM | 8,662 Views
There have been so many man rated quad copters, EDF powered hoverboards, mini helicopters, that only go 5 minutes, can't get above ground effect, or never got finished, the Flyboard looked like more of the same when in fact it was different. The key is to consider too this day, the smallest flying machine that actually works is the original hydrogen peroxide jet pack. It goes 30 seconds.

The Flyboard is the 1st to be at least as compact as the jet pack, but go much longer than 30 seconds. It uses 4 hobby size jet engines at $10,000 each. The fuel is in a back pack with a hose going down the pilot's leg. If the fuel line gets kinked, he loses $40,000 & dies.

The remote control only controls thrust. The pilot leans to control direction. It probably has foot switches, but his feet are rigidly mounted. There could be a trick involved in rigid foot mounting, yet allowing enough motion to provide user input.

Hobby jets probably have enough response to stabilize it by varying engine thrust. There's no thrust vectoring or reaction control thrusters. 2 red EDFs on the sides counter the torque of the jets & provide yaw.

There's nothing in it which couldn't have been done 10 years ago, except for coming up with the money. Borrowing $40,000 was once equivalent to borrowing $400,000 today.
Posted by Jack Crossfire | Apr 19, 2016 @ 11:04 PM | 8,987 Views
To not feel so bummed about the home made copters of years ago being stressful & difficult to keep out of harm's way, it's time to start compiling Neistat's quad copter crashes & tribulations.

boat crash:


loss of signal:


bridge crash:


So basically, despite years of multiplying valuations & redundancies, even the most foolproof quad copter still isn't much more foolproof than the old days. The attempts at obstacle avoidance by sonar & IR obviously haven't translated into anything meaningful. Neistat explained that he gets away with flying by having 4 quad copters & chewing them up.


He explained that he was getting all the selfie shots by semi autonomous control, not by any dedicated feature:


Ergonomics were probably the biggest factor in doing it manually. Given the amount of flight time & length of the final shot he gets, it's probably too cumbersome to set up a "cable cam" , waypoints, "leash cam", or geofence.

Still suprising he has to carry all that gear. There would be no way he could use a 3DR copter because they're too big. The Phantom is just small enough.

Ground vehicles have no worries. They can precisely navigate the city streets. Combining their single handed controller with a quad copter would be the ultimate selfie system, 10 minutes at a time.

The videos of the Phantom 4 at low altitude do look rock solid precise. It uses sonar for altitude & dual cameras for optical flow, but also fuses that with the accelerometer.
Posted by Jack Crossfire | Apr 13, 2016 @ 08:54 PM | 9,080 Views
The amount of soot appears related to the amount of time the surface spent at ambient temperature, so the gradations in soot can show the amount of LOX left in the tank during each re-entry burn. 33% of the total LOX capacity was required for recovery. Of the 33%, finer gradations show the 1st & 2nd re-entry burns with 15% left over for the landing burn. The line dividing black from white would be the edge of the common bulkhead, since there is no intertank section to provide a smooth gradient.
Posted by Jack Crossfire | Apr 09, 2016 @ 08:14 PM | 9,073 Views
Managed to get the USB->serial dongle working in VirtualBox, since it's a ttyUSB instead of a ttyACM. The problem is the gimbal has to be turned on after the firmware update tool is already listening. The firmware update tool waits for a start code so it can force it into bootloader mode. PWM did indeed have to be off. TX came from the pitch PWM. RX went into the yaw PWM.

So the Feiyu turned out to already have 1.14, the latest firmware. That left waiting for another firmware update in the future or programming it from scratch. Feiyu already discontinued the mini 3D, so another update is unlikely.

Tearing it down revealed a bewildering nest of miniaturized boards which would have to be reverse engineered. The same board is replicated for each motor. There is only 1 IMU.

Next, we have an MV358 op amp, given away by some RC pairs next to it. It probably amplifies a signal from a chip marked only 01281000, undoubtedly a hall effect sensor despite the lack of any Goog results. It's directly under a magnet on each motor which serves no purpose other than giving the motor's orientation. These magnets are circular polarized to give a varying field for each position.

The same firmware probably runs on each board, relying on the placement of jumper resistors to know which board it is. Communication between the boards, how to change the firmware with the existing bootloader, how to control the motors are all the great tasks. It would have been a lot easier if they just allowed configuring the product.
Posted by Jack Crossfire | Apr 09, 2016 @ 02:45 AM | 8,675 Views

Another small step forward. Landing at sea increases the amount of mass which can be launched on a reusable rocket. Still up to the voters & government to determine when humans will finally be able ride it. Their 1st launch of a human is entirely dependant on your continued support of the CCDEV program. The human mission to low earth orbit would be the easiest to recover the booster from, the baseline mission for the reusable system.

You would think there would be competition between customers to be the 1st to pay for a used rocket. It would be quite a publicity boost. The 1st is going to be the one in Wikipedia for all time or at least as long as it keeps raising donations.
Posted by Jack Crossfire | Apr 07, 2016 @ 03:05 PM | 8,450 Views
Current usage with camera recording at 8.4V:

0.85A with motors not deflected
2.3A with all 3 motors fully deflected

The old pro doesn't work without battery. There's no point in using the power supply umbilical unless you're previewing video. Even then, the power lead should be desoldered. It's easier to use the pro battery in its included spot than carry around an extra gimbal battery.

A dummy battery could go in the pro that would trick it into working without a battery. It probably just needs to see 4.2V on a pin, but no spare battery exists to sacrifice.

Current usage without powering camera at 8.4V:

0.25A with motors not deflected
1A with all 3 motors fully deflected

When powering the camera, a converter reduces current usage for higher voltages. Without powering the camera, the current rises slightly for higher voltages, but with no increase in torque. Minimum current is always 0.25A. The torque seems just high enough, but could go higher without burning out the motors.

Motor control is quite a bit more robust than past gimbals. There's no skipping or studdering. It's like it has encoders giving it motor position, but it doesn't. It's using gyros attached to all 3 motors to gleam phase in addition to orientation. It seems to have an algorithm change which invokes the gyro based encoding when the angles get offset beyond a certain amount. This allows it to recenter instead of studdering.

It was deemed good enough to hard code the mode & speed in...Continue Reading
Posted by Jack Crossfire | Apr 04, 2016 @ 12:39 PM | 6,836 Views
The 1st assembly of the Feiyu was disappointing. It wasn't as transportable as hoped, but it was more compact than keeping the shock absorbers. Wires hung out everywhere, but the assembly can probably be wrapped. The aluminum arms are going to bend over time. The bolts need reinforcing tubes. There's not enough clearance from the handle to easily turn an allen wrench. The pins for calibrating the horizon need to be flush on the handle.

The power switch managed to stick on by reflowing the hot glue after gluing it on. Reflowing hot glue by blasting it with the heat gun after initially tacking it has been effective at sticking difficult parts.

The power switch was deemed necessary because the Feiyu has to be powered on in the orientation it's going to stabilize in, but it's a fragile arrangement with lots of wires. A quick test should reveal if the power switch is necessary or if the battery plug, a MOSFET with delay, a tact button, or app button for enabling the Feiyu can do the job.

It was decided to remove the 2 pots for mode & speed. Those are better controlled over bluetooth app. The voltage regulator needs to be replaced by a 3.3V & bluetooth connected to the debugging port. Need to measure the power consumption of bluetooth.