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Archive for January, 2017
Posted by Jack Crossfire | Jan 31, 2017 @ 06:49 PM | 5,481 Views
So the bluetooth board caused a power supply noise problem when it used the TDA1517 as an amplifier. Must figure out how to defeat power supply noise, 1 of these days. Decided to discard the entire TDA1517 board & just use the bluetooth board with the old speakers because it would be the lightest.

The bluetooth board had some kind of series capacitor network feeding the amplifiers.

1uF + 20k + 100nF + 20k

Replaced it with just a


to try to make it louder. It now seemed just as loud as the TDA1517. The chinese datasheet showed a 58nF + 30k.

The BK3254 had no datasheet, but if holding down the power button to turn it on was annoying, it could be powered directly by applying 3.3V to pin 16. Unfortunately, it automatically reset this way so some other voltage was missing, perhaps 4.2V on pin 17. Never could find a 3.3V source on the board, so perhaps the chip implemented its own regulator & power button control.

Also, cable management nightmares proved a speaker is best powered by its own battery instead of the vehicle power.

It's probably best to use a bluetooth speaker as is, except for replacing the speakers & enclosure to make it lighter & louder.

In other news, discovered phones probably aren't cracking when the vehicles roll over but when they jump off curbs. When the vehicles always carried a shirt, the phones had cushioning & didn't crack. With a severe winter leaving the vehicles devoid of a shirt for many months, phones started cracking like crazy. They're also self destructing to get cheaper & thinner.
Posted by Jack Crossfire | Jan 28, 2017 @ 08:39 PM | 7,015 Views
The lion kingdom still remembers when the most $10 would get were the cheapest, tiniest, most horrible sounding speakers which plugged directly into a walkman. The sound was completely unintelligible, but what a novelty in the old days to hear a walkman through any portable speaker.

There should be no disappointment in 25 years later, what would appear in Walmart but $10, Lipo powered, bluetooth speakers which actually sound as good as a boombox did. It's not just a case of something getting cheaper by getting smaller, but a lot more getting cheaper.

The purpose of this was not the speakers, but to gain a bluetooth receiver for a lot less than $parkfun's $25 bluetooth audio module. Managing the headphone cable had become quite a chore in 6 months of driving around with it. Sadly, the new speaker would be too heavy & quiet to use intact. It would require a much bigger robot to move around a decent speaker & loudness has taken precedence over quality.

The teardown was completed & the electrical signals probed.
It uses ANT8110 class D amplifiers which take 5.5V & output 3W. The only datasheet was purely chinese except for 5.5V, chipsourcetek, 3W, & class D. Though the reduction in voltage would be a huge convenience, it wouldn't be as loud as the 6W TDA1517.

The receiver is a Beken BK3254. Analog audio comes out of 2 pins at line level.

It requires 4.2V power at the battery terminals to power the ampilifier. The receiver can work on...Continue Reading
Posted by Jack Crossfire | Jan 21, 2017 @ 08:30 PM | 5,906 Views
1) A robot dog which can go 10mph & traverse curbs.
2) A way of editing text on a tablet which is as fast as a keyboard + mouse.
3) Action cam with image stabilization

Quite different from years ago because the autonomous RC car is gone. That was deemed very impossible, for the moment.

1 is probably going to happen in the next 30 years. Thinking of ways to do it with standard servos. The mane problem with 10mph is the actuator needs to be more like a spring to generate a bounding movement. There could be a slow movement to charge the spring followed by a fast discharging movement. Traversing curbs would use fixed movements rather than adaptations based on sensor feedback. It would have to be passively stable.

The leading idea is standard servos for the knees & hips. Both rear hip servos would connect to a common, shmick servo. Only the standard servos would move for walking. For bounding, the shmick servo would fire simultaneously with all the rear servos to jump. If the servos are cascaded, the simultaneous motion of the 3 servos should produce enough velocity. The jump would lift off the front legs, then land on the front legs. The front legs would steer & allow the rear legs to reset.

This might move more like a rabbit than a dog, in which case the front legs would need another shmick servo, but the same general idea would provide any bounding movement.

2 is probably impossible. The Goog had some research which compared keyboards to...Continue Reading
Posted by Jack Crossfire | Jan 21, 2017 @ 12:46 AM | 5,384 Views
So the Kyocera Hydro was a total failure. It was too slow to even type on, let alone load any web pages. The mane problem was the camera had permanently blurry regions. The lion kingdom didn't realize how important the phone cam had become until it didn't work. Japanese electronics once again came in far behind, subsidized by quantitative easing but not improving in 30 years.

In the world of phones, no matter what the problem is, the solution is to change providers. Boost Mobile had become cheaper than Virgin in the last 3 years. Virgin jacked up LG's bottom end, but Boost was still affordable.

The LG Tribute HD is a miracle for the price. It's lighter & thinner than all the other cheap phones. While noticeably slower than its predecessors, it's still faster than the Kyocera & a $50 screen of this resolution was unthinkable 3 years ago even if it's nowhere close to an iPhone. The camera isn't iPhone quality, but not a total failure like the Kyocera. LG cameras have always been just good enough. The internal flash was finally big enough to eliminate the need for an SD card. The Moto X wouldn't have been worth it.

It may have been inconsequential for someone who lived 30 years ago, but a screen where you can't see the pixels now seems essential. Part of the appeal may be that it looks like an iPhone.

Interestingly, below the Tribute HD are now $30 phones with decent screens, which can be used as real cheap standlone computers without a plan. A phone can be just a car music system or a dashcam for a lot less money than a stock device.

The day job has real nice phones which require hideous plans. The Galaxy S5 needs a $55 Verizon plan.
Posted by Jack Crossfire | Jan 16, 2017 @ 11:46 PM | 4,978 Views
The 3rd LG Tribute disintegrated during a romp in the canyon. It lasted only a few weeks. Single women may have high medical bills, but their lack of exercise probably saves a lot on phones. Thus ended 3 years of Lucky Goldstar being the bottom end. They once adorned the Target shelves at $40. The Goldstars are now high end. The new low price leader is the $50 Kyocera at Target. For $10 less, there are Alcatels online only.

The low end reduced all their processors from 1.2Ghz to 1.1Ghz. They reduced all the cameras from 1920x1080 to 1280x720. It's 1 of those phases of economic stimulus where lower performance is rising in price to keep everyone employed. Mercifully, the Kyocera doesn't turn on when tapped. That bug definitely pushed the limits of millenial debugging ability.

Sadly, there's no way to get the contacts off the Tributes. Once their screens cracked, all the data was inaccessible.

Tehan falls (1 min 54 sec)

What a cracked LG gets you.
Posted by Jack Crossfire | Jan 15, 2017 @ 11:16 PM | 5,203 Views
Self Driving BASE 1 Rover - MountainTrack (5 min 1 sec)

This nugget caught the lion kingdom's attention last month. It seems to be doing the impossible: navigating a mountain dirt road with lots of shadows using only machine vision. For the 1st time in 11 years of UAV blog posts, there was no mention of GPS even being offered in the product. Of course, it didn't stay to the right like a running pacer has to do.

Knowing a convolutional neural network is just a storage & recall mechanism for images, it could have been done by training the neural network on many manual drives through the same 5 minute path. There's enough detail besides the path for the rover to ignore the shadows, determine where it is & steer to prerecorded headings. How the rover determined where it was in relation to the center of the path would be another trick. It could be a neural network trained on a bunch of offset camera views or it could be simple optical flow.

The key is the vertical detail from the trees & mountainside adding extra edges besides the sides of the path. It wouldn't do well on a bare path shaded by trees outside the camera view.

In other news, keeping with the modern slogan that the programming language is the computer, Tesla hired the guy who invented Swift & invented the LLVM as the VP of autopilot. 20 years ago, they would have hired a networking expert & 10 years ago, they would have hired a video expert. It would make sense for Tesla to invent its own programming language, since that's what everyone else is doing. Perhaps the world needs a programming language for neural networks instead of a library.

The LLVM has a good chance of replacing GCC. GCC has enjoyed a 3 decade reign, but ever since running it for the 1st time on an HP, it was slower than any commercial compiler.
Posted by Jack Crossfire | Jan 12, 2017 @ 07:41 PM | 5,297 Views
There was a lot of hype about hybrid apps in 2014. Based on the internet, the verdict is there's absolutely no advantage to either method. The lion kingdom's experience:

GUI & speed requirements ended up beyond what the standard hybrid libraries could do without major effort. The browser incompatibilities & replicated effort when trying to optimize the interface for each phone were just as bad as native.

4 months of work on a webview implementation yielded nothing, with so much expertise being required in web development to achieve minimal results that the IOS & Android developers ended up going back to other tasks on their own platforms until another developer could be hired for the hybrid part.

It ended up requiring more people than if the hybrid part was done natively.
Posted by Jack Crossfire | Jan 04, 2017 @ 11:05 PM | 4,967 Views
They're a dime a dozen, but still not sold commercially. Would feel sorry for anyone dumb enough to have to pay for one. The mane desire was to reuse foot pedals that were already around, but the Yamahas have an open circuit when they're active & closed circuit when they're inactive. The only solution was BJT's to invert the switches.

Making it work without batteries required 247k pullup resistors, so the pedals pulled down the bases when they were inactive & the camera bias voltage pulled up the bases when they were active. When the bases were pulled down, the resistors couldn't draw too much current to the point of triggering the shutter so they had to be large. It's an interesting use of a voltage to turn itself off.
Posted by Jack Crossfire | Jan 04, 2017 @ 01:03 AM | 5,270 Views
After many miles, the long awaited conversion to LF353 happened. It's ever so slightly subjectively clearer, but the speaker is too overloaded to hear any difference.
Posted by Jack Crossfire | Jan 02, 2017 @ 06:06 PM | 4,894 Views
As expected from the anomaly page


they had to abandon supercooling at least part of the propellants. The helium will be warmed up to prevent pockets of frozen oxygen from forming. More of the engine exhaust will be bled off to pressurize the tank instead of using helium. They confirmed voids in the COPV laminations pooled liquid oxygen. When the liquid oxygen froze, it expanded & burst the laminations. More specifically, it was a void between the aluminum inner liner & carbon fiber overwrap. To save money, the overwrap was launched with voids.

You normally think of a tank being a barrier between stuff on the inside & stuff on the outside, but the overwrap on a COPV is actually saturated with stuff from the outside. The total propellant load thus consists of everything the engines need + a little bit for the COPV's to soak up. Presumably, the oxygen impregnating the tank can solidify as long as it doesn't form large pools.

Along with more expensive struts, they'll need super high tolerances for the overwrap, so explosion by explosion, it becomes less off the shelf & more precision specked like a shuttle. NASA spent years troubleshooting voids between solid propellants & booster walls. They avoided the explosions, but it took immense manufacturing standards.

They mentioned other changes besides warming the helium, but not what they were. They revealed the other changes involved spending a longer time loading propellants. They implied the helium loading procedure was changed during the fateful day from what it was in previous launches.
Posted by Jack Crossfire | Jan 01, 2017 @ 03:21 PM | 5,244 Views
After 6 years on the wagon train taking heroic efforts to defeat noise, the preamp was redesigned again. The discrete transistor amplifiers are now an LF353. The discrete transistor was nifty, but impractical for fully balancing 2 channels. The LF353 subtracts the differential inputs & amplifies the result with minimal components. This eliminated the noise completely & finally allows the Zoom to record 4 channels. It also seems capable of sharing the power supply with the Zoom without any noise, but it's not soldered for it.

The mane problem is the pots being too close together. The mane cost in going to 2 balanced channels is 2 stereo pots & 8 wires to connect them. Previous work with digital pots ran into a lot of noise from the SPI & a display to show the current level. The balanced inputs may defeat the noise, but the analog controls have proven simpler.

The LF353 circuit had to deviate from the goog slightly. The 1k's had to be fixed. Only the 100k's could vary. It needed 1k's on the outputs to isolate it from Zoom noise. Spudger diodes prevent the 48V pop from blowing it up. The virtual ground is 5V. It needs 12V to be happy.

All support for 2V microphones & dynamic microphones is gone. It's now just a phantom powered 48V preamp.

The moral of the story is any microphone is going to need a balanced amplifier in its 1st stage, right down to your cell phone mems microphone. The balanced signal needs to be retained all the way until the line level or power supply noise will always be a problem.