Sonar on the micro quad was decidedly worse than the Syma X1. The motors are noisier & there's more airflow. Attempts to move it closer to the center failed. It got stuck at 0.3m. EMI from the power distribution board could be jamming it or it could be unlucky airflow. Foam wasn't rigid enough to keep it pointing down. There is hope office carpet yields better results than apartment carpet.
The MB1240 runs at 20V & the highest you can go without serious electronics is 30V. A dual transducer at 30V might do better.
Then, compass interference from the power distribution board has returned. There is a config parameter which records the mag readings to a file, during a hold down test. That can be graphed & used to set mag offsets in the config file. The hold down test doesn't give the true offsets during a flight, so the numbers need some trial & error scaling.
Only moving the mag far away would completely eliminate the interference. That's not going to happen with the MPU9150.
Finally, the altitude given to the PX4flow is degliched but giving worse results than glichy altitude, so it needs to be tested. The PX4flow does a lousy job subtracting angular movement from translational movement, yielding roll oscillation.
It would probably give better results if the pixel flow was completely processed on the flight computer instead of relying on the PX4flow to convert the flow to meters. The sonar forwarding would go away.
Comca$t finally closed the door on getting local channels in the digital format they are aired in. For now on, they'll be encrypted & only available via an official Comca$t box after paying for the digital service. If you don't pay for the digital service, you'll be reverted to the analog low definition quality last seen in 2001.
It's a horrendous regression in service. So many people must already be paying the $100+ for digital service that no-one complained. The good news is there wasn't anything worth watching on TV in years. It might have been amusing to see some of the recent shows or a really important sporting event in HD, but they have no value.
The 3rd party DVR's & home theater PC's keeping Comca$t's CEO out of the $5 billion club have finally been squashed in 1 swift stroke. Your only recourse is to drive within line of sight of sutro tower with a portable recording device.
The goog automatically searches for "BCM7002 datasheet" for you, because so many guys have already tried hacking in. There's no unencrypted transport stream exposed on a pin for you to capture. There's no way to rip off the keys from the chip. It probably does a handshake to ensure your account is paid for, then receives a new key.
The transport stream is probably buffered in the SDRAM. Some crazy Russian could probably extract it with a really fast logic analyzer or SDRAM sniffer.
Micro quad flies some waypoints, then a position hold test over plush carpet, using a PX4flow modified to use an MB1240 sonar module.
Based on the previous video of the TCM8230 over carpet, the PX4FLOW is a huge improvement. It actually holds position quite well over plush carpet & below 1m. Replacing the MB1043 with an MB1240 & translating the serial protocol from cm to mm is required.
The sonar still has issues above 1m. It glitches to 5m when it can't detect a reflection. Sometimes you want it to send 0 when it reads 5m & sometimes you want it to repeat the previous reading when it reads 5m. It still glitches, despite this algorithm.
It's very heavy, so it handles the wind quite well. Crashes require a lot of repairs & propellers.
Eons ago, back when Goo Tube was only 320x240, the NYSE was below 9000, & phones still had keypads, I got a robosapien for $50. It was the 1st "learning toy" of any note. Manually manipulate the arms & legs while recording & it could play back the manual motions with some level of accuracy.
Actually got it to walk around on carpet, way more than its design. It needed fully charged batteries. It under extended the motions because the pots wouldn't completely follow the limbs.
It had a timer which made it record a waypoint after a certain period of not moving. That recorded a lot of wrong positions if you didn't hit the right position on the 1st try. It had a fairly high threshold for being considered stationary, making the training motions ridiculously fast.
These factors made training it a very cumbersome affair. The training was an extremely exaggerated bunch of movements that resembled none of the playback. It ended up pretty boring & tedious, compared to programming movements from a computer. The novelty was supposed to be the fluid, biomorphic movements it could produce during playback, I suppose.
It did look pretty fluid compared to previous toys, but just like graphics in a computer game, the eye candy only went so far before the logic of the game & the ordeal of teaching it by hand took precedence. There are much less visually appealing games which...Continue Reading
Another piece criticizing the F-35's suitability. It was originally appealing, because of its simple mechanism for hovering compared to the Harrier. As the conspiracy theories have mounted, other factors have to be considered.
It never looked very maneuverable, but modern flight by wire can make anything maneuverable. It was tasked with doing many things: hovering, carrier landings, bombing, dogfights. Once again, flight by wire was advertized as making everything accessible to a single airframe.
1 obvious downside is the pilot can't see backwards, instead being expected to rely completely on radar & the opponent not being stealthy.
Another downside is the internet has increasingly decided there are limits to how much flight by wire can compensate for aerodynamics. By the time the F-117 was retired & destroyed, it was unanimously considered suffering from very lousy aerodynamics which the software couldn't compensate for.
Finally, there's the issue of why 3 variants of the F-35 are required. Why can't all of them hover, land on a carrier, & do whatever the air force does? If taking out 2 of the 3 options makes them better at 1 mission, wouldn't they be better if the rest of the airframe was optimized for 1 mission too?
So it's probably not as good as the A-10, F-16, F-18, & F-14 were at their jobs. It's probably better than the harrier for its...Continue Reading
After 5 years, the mighty HP has finally been outdone by television standards. The HP did 2560x1600 at 30", which was way beyond any TV resolution for many years. No matter how big a TV was, it could never do more than 1920x1080.
You might say it made day jobs involving TV standards a turn off. It was a vacuous size for opening many windows, having giant fonts for text editing, & viewing photos at nearly their full resolution.
But now, China has unleashed the next generation of TV's on the world. 4096x2160 at 85". 60% more horizontal & 35% more vertical resolution than the HP, with enough size to completely immerse you. It's the next must-have status symbol of women my age.
Even if you're not a jet setting 38 year old blond hottie with $40,000 to burn, 4k is what every TV is going to use, right down to the HP's $1300 tag. Of course, modern 30" monitors are $800 & have much better color. The HP always had garish colors.
A TV would be a buy for me, if it was bigger & higher resolution than a computer monitor. Everything used TV's in the 1980's but TV's later suffered from being locked into low end standards while computers got ever higher resolution. 4k might be the resolution to tip the scales back towards a TV for everything.
The STM32 can do a 1024 point FFT in 5ms. There's also the unknown matter of computing magnitude, normalizing, making it probably 10ms. At 10 sweeps per second, that gives only 10 FFTs per sweep.
That comes with a 8192 byte tag.
2048 bytes: analog capture window
2048 bytes: imaginary value window
2048 bytes: simultaneous capturing of next window
2048 bytes: normalization table
Then, the 1st 256 samples from each window are stacked on a polar projection. Only the 1st 1/4 of the window has had useful range. That comes with a 2560 byte tag for the current projection & 2560 bytes for the previous projection for 10 FFT's per sweep. 50 FFT's per sweep would take 12800 * 2 bytes.
Motion tracking in a polar projection would take some doing, but be the most efficient solution. An additional 5120 bytes of ROM might be required for a lookup table to convert the polar pixels to square pixels for motion tracking.
Then, some 1024 bytes of scratch memory might be required, bringing it to 60416 for the 50 FFTs per sweep or 19456 for the 10 FFTs per sweep.
To rotate the FFT's & motion track a square projection would take 256kbytes to retain the full resolution. It would involve a similar lookup table to only track filled pixels.
No matter how limited the microcontroller, the resolution & speed of the sampling can always be scaled down to fit. The difference is only in the resolution of the output, not whether it can...Continue Reading
A static radar antenna doesn't give a consistent reflection pattern as the aircraft pitches & rolls, so it needs to sweep a certain angle so something is always detected as reflections come & go. Exactly what angle to sweep is a matter of experimentation. The worst case is 360' 20 times per second.
Making synthetic aperture radar with hand tools is harder than it looks. The fastest a home made gadget ever spun was 60rpm. To get 20 position updates per second, the required RPM is 1200.
There is the idea of a spinning reflector under a stationary radar. A flat piece of metal in exactly the right position actually directs the radar beam quite well.
It's conceptually simple, but requires an exact 45' miter cut to mount the reflector & the reflector needs to be exactly aligned on a separate jig under the radar. The reflector is huge, moves too much air to spin fast enough, makes a lot of vibration, & decreases the radar power. Errors in alignment from fabrication take away more power.
It can use a very long rod attached to a motor. The rod needs to be exactly parallel to the motor. It couldn't be made by hand tools to spin very fast & would need a large diameter to counteract the vibration & drag.
Another way is a triangle mounted on a pancake motor & the motor mounted on a long rod. It could spin faster.
Making a shaft coupling is still out of reach for hand tools. Mounting something flat on a pancake...Continue Reading
Found the story intriguing. Batteries remane fickle things. Their total charge is still only estimated by stopwatches & coulomb counters, but there is no dip stick for a battery. Even a pilot experienced enough to keep 1 eye on the flight time while the other eye is on the 5000 other details still is often surprised when a battery comes up empty ahead of schedule.
Sometimes you forget to charge batteries. Battery chargers sometimes don't finish charging because they overheat or their own supply sags. Sometimes they don't start charging because of a balky button or a poorly designed user interface. Sometimes they report maximum voltage despite no longer holding a full charge.
A return to launch feature when the battery is low also remanes fickle. GPS comes & goes anywhere besides a wide open field. Is the return to launch feature supposed to count coulombs & maintain a database of every battery's capacity in order to determine when to end the flight? Should the pilot enter in the current battery ID or should the batteries have ID chips, raising the cost & complexity?
It's yet another one of the variables & details that keeping something in the air still involves keeping your mind on. There is still a lot of room in the current state of reliability to keep the price, complexity & training beyond the reach of hobbyists before the personal drone becomes as ubiquitious & hand off as the marketing campaigns depict.
So a phone still can't outdo a dedicated mp3 player for a car. After the Sansa broke again, it was a rough 10 hours of driving, fighting the Android music app & getting mono audio out of its 4 conductor headphone jack.