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Posted by Jack Crossfire | Apr 26, 2009 @ 06:08 PM | 4,760 Views
Take just enough courses to qualify for loans & borrow as much as you can. Use the money to build a business or build something that could be used in a business. Ideally it's part of the degree, but most of the time it can't be & you're more motivated if it's not.

That's how Google, Netscape, Microsoft, Sparkfun & most famous business got started.

In centrally planned economies like US, the money always lags the value. The money goes to what was valuable 10 years ago while the people really want something newer, from China. So instead of waiting for all those congressmen to catch up with what people want, U take those student loans & build what's valuable now. Then when the economy catches up, you're waiting in the door.

Now student loans R free & you have a new age where it's government's responsibility to pay off all debt. Using taxes to finance all debt is going to be as basic as using taxes to fund roads. U need to borrow like no tomorrow.

U think those people working make any money? Of course not. They grow their cash balances by 10% a year if they're lucky & watch the cost of living rise 20%. Meanwhile you're getting student loans for 1% & watching the value of debt fall 20%. You're not making money if you're not borrowing.

Circuits that don't work

Before U completely fall asleep from that, Vbus works in the following configurations.

All cases with sonar plugged in.

Sonar not plugged in & not compiled for sonar.

After busting an RF choke & a diode, decided the problem with Vbus is a low frequency ripple that can only be defeated by a voltage regulator, but since we need 5V, it would take a very expensive DC-DC converter followed by linear regulator. The sonar probably works because it grounds everything to Earth.

The only concern was if a change in the sonar wiring broke this strange behavior or we wanted 1.6mbits without sonar. In the mean time, U've got the comb filter to reject low frequencies.
Posted by Jack Crossfire | Apr 25, 2009 @ 05:47 PM | 5,436 Views
China launched another spy satellite for growing food.

India launched another spy satellite for Israel.

Russia launched another spy satellite for Italy.

US announced its moon program has been... wait for it... delayed by budget cuts.

Ares 1 was reduced from 6 seats to 4 seats to reduce parachute costs. When asked how US would meet its space station obligations, NASA said that's what Russia is for.
Posted by Jack Crossfire | Apr 25, 2009 @ 01:50 AM | 4,450 Views
According to your government, the wind was 20mph, gusting to 29. By the time we got the PID limits increased to where she could handle it, there were only a few minutes of battery power & it was dark.

It was the PID limits & not the PID gain that did it.

In this wind, with the shims reducing vibration, the low RPM motors, U couldn't hear Vika 1 at all.

Didn't bother facing away from the wind.
Posted by Jack Crossfire | Apr 24, 2009 @ 02:19 PM | 4,504 Views
So got Vika 1 all buttoned up for flight, moved all the gear down to Silicon Valley for some daylight photos, & sure enough, the ground controller was dead. Couldn't get it to show on the USB.

Drove all the way back to Rain Ramon & it worked on 1 of 3 AC adaptors & no batteries. So instead of trying to figure this one out, we went to Vbus & it worked.

The answer is yes. The USB has enough juice to power the PIC at 48Mhz, the XBee, the GWS Pico receiver, & the sonar. U just saved $100 on another Lipo.

VBus is really noisy, so you can't get much higher than 256kbits without serious filtering. Decided to try that denoising RC circuit the Goog tends to spit out & it didn't work. We'll be back to what we already know in future commutes.
Posted by Jack Crossfire | Apr 23, 2009 @ 09:18 PM | 4,359 Views

Most LiPos last longer if you land & let them cool off repeatedly, but with some old batteries, they can't fly at all after being used for anything. Even if they only powered a ground station or only flew half their capacity, for the next flight, they're completely dead.

They seem to require a higher temperature to handle current when not at full capacity & flying keeps them above that temperature. If anything puts them below full capacity & they get cold, they can't generate enough current to fly anymore.


U already know how day jobs R going away & being replaced by 1 man online corporations selling limited edition refrigerator pens. Well, what happens when everyone loses their jobs & U have 500 million limited edition refrigerator pen corporations? Are day jobs going to be the new way to get rich?

There's only so much 1 man corporations can do. Once U get beyond the limited edition refrigerator pen, it gets harder & harder to produce something substantial without investment capitol, employees, management of people, accountability, wage slavery.


Managing people sux. Your boss is miserable. U think he treats U like s**t because he's happy? He has to manage idiots who aren't smart enough to be managers & his resume has to say he only managed losers. What manager would say he managed the best? That would mean his subordinates were better than him.

U always think when U get into management, you'll be powerful, rich, & famous. Then when God finally comes down & ordains U a manager, guess what, U now have to be a loser in 3rd person.
Posted by Jack Crossfire | Apr 22, 2009 @ 04:19 AM | 4,260 Views
So, decided to forget about crosstalk & go up to 227khz becuz the Matsushitas have lots of destructive interference & nodes. Trying to do 2 things simultaneously in using a hardware ping generator that can't ping shorter than 0.013 seconds & a there's a standing wave shorter than that ping.


We point 2 point solder because it's free & instant. It would take several revisions & several weeks to get a PCB right. Several months with batch PCB. One question is, with so much historically automated manufacturing now using manual labor in China, will P2P soldered circuit boards return?

Human labor would have to become cheaper than the cost of large numbers of PCB's. It can become cheaper through a sharp rise in oil costs. Petroleum is the basis of all materials & mass production.

Look, there's going to be an oil embargo. U can't expect OPEC to keep making small cuts & holding out for later. They're going to shut it down & demand price controls. You're going to have smaller numbers of each thing being made because raw materials & automation R going to be too expensive. When oil goes higher, humans get cheaper.


You'll be happy to know Calif* was once again as hot as it was in April 1989, so the inland urban heat islands didn't enhance the seabreaze & freeze the day job area as feared. After a scorching 1989, the spring of 1990 was also very scorching, with romantic warm nights, until Mt. Pinatubo erupted in 1991 & froze U solid. The Pinatubo dimming caused a rare rainstorm that summer.
Posted by Jack Crossfire | Apr 21, 2009 @ 04:18 AM | 6,925 Views
There U have it. The fabled Matsushita 0D24K2. The driver is the same size as the Maxbotix, but it has a huge board to resonate 1/2 the frequency. These R the kind used in super expensive motion detectors.

More importantly, finally got the transducers to take op-amp output. Had a lot of theories on why this didn't work, ranging from extremely low impedance to frequency response, but it was dead op-amps. That gives U 20V peak-peak on the emitter.

8V p-p

Is what U get from the 5V bus. Works best within 0.25khz of 24.26khz. The shroud moves that to 24.50.

20V p-p

Is what U get directly from the LiPo. They can go from 24.74 to 23.35khz without shroud.

The Maxbotix's only worked at 38.45khz so U can't combine a Maxbotix & a Matsushita to save weight. No doubt the Matsushita's at 20V R much more powerful than the Maxbotix's at 10V, but you're still a few commutes away from flight test #1.

TODO: Try mounting the emitter a few inches below the fuselage.


If nyquist < signal freq, alias = samplerate - signal freq
If samplerate < signal freq, alias = signal freq % samplerate

With the draconian optimizations, we now capture 3 channels at 66khz. Top speed is 73khz per channel with crosstalk.

Like everyone else, we're probably going to forget about Facebook just like U forgot about myspace & the Jack Crossfire blog. Going to skip Twitter & go straight to Loaner. Loaner is neither single sentences nor blog posts. Loaner has no content. U get paid millions of dollars for future content.


All the friends on facebook are based on real events, not events on social networks. So who's creating current events to base future friends on?
Posted by Jack Crossfire | Apr 19, 2009 @ 05:35 PM | 3,863 Views
After banging on reflected sonar enough, here R your notes.

Get ready for 2ft of deadband if U want to use direct amplitude measurements.

U can reduce deadband by using integrals because they measure the total power of 2 overlapping waves.

Integrals require very high samplerates & reduce the software samplerate to 120khz, so they can't be done in software.

Use a lowpass filter to make a threshold. Hold the transducer at +0V for 1/2 of the deadband, then float it for the rest of the deadband to shorten it.

The shroud made no difference.

A unidirectional system just needs the flight computer & 2 op-amps to generate pings.

Vika III will be a spin stabilized, dual lift fan with no IMU, 1 LED for operator orientation & 1 photodiode for heading. If U stop raising taxes, she may get a pushbroom camera.

We're back to 3 transducers on the ground & much lower expectations.


In the old days, it took years to forget about heroines. Then we met lots of married men & realized it sucked. After Russian Heroine, it's probably back to taking years. There R good days & bad days. One day you're productive. The next day a strange memory or a new nerve connection turns U into an American.

We're at the age where U can expect to fall in love 1 more time, but it's going to be a wrinkled prune. Going over facebook, either all your former heroines became housewives who stay home & update facebook all day...Continue Reading
Posted by Jack Crossfire | Apr 19, 2009 @ 03:19 AM | 3,834 Views
That's right kids. After saving us from OPEC & inventing Sissel, Novay finally pulled off its next hit for us. Now if only Europeans could give up their corny video effects.

It flies itself indoors. It probably uses RTK GPS. It definitely uses actuators for cyclic.

PD-100 Prototype - Mission (1 min 32 sec)

PD-100 Prototype - Flight testing (2 min 28 sec)
...Continue Reading
Posted by Jack Crossfire | Apr 17, 2009 @ 06:12 PM | 4,076 Views
After watching videos, we can tell U exactly how the Wowwee Bladestar works. Its CG is slightly off center, causing it to lean forward if the fuselage is stationary. The fuselage naturally rotates real fast to neutralize the CG & keep it vertical. By pulsing the counter torque fans, the fuselage can hesitate at 1 point in the rotation & cause it to lean in 1 direction.

Avoiding obstacles requires merely tying the fan voltage to the IR reflection voltage. When the IR reflection goes up in the turn, the fans speed up, causing it to hesitate at just the point in the turn where the IR sensor voltage is maximum. That makes the fuselage lean away from the IR sensor.

Now what if instead of counter torque fans, U had counter rotating lift fans that pulsed to make an unbalanced, rotating fuselage lean. What if U went all the way & put GPS on it for position & used a visible light sensor on the spinning fuselage to detect heading by making a 1 dimensional 360` image of the surroundings.

U think U can handle it?
Posted by Jack Crossfire | Apr 17, 2009 @ 04:17 AM | 3,777 Views

Well OK, would probably get more of the aerodynamics lectures if the aerodynamics course was also available. All we do is strap together motors & use software to make it fly, so no-one in this blog ever cared about aerodynamics.

He had some nuggets about how they could fit together baked equations for cones, spheres, & wedges to verify the CFD results.


Got the go ahead to begin reflected sonar altitude. We're only deep into reinventing a Maxbotix from scratch because of the random trigger latency in the product. It's pretty rough because it's using a shroudless transducer, 260khz sampling, pure digital processing, raw amplitude.

Pretty confident the Maxbotix's have enough range to fly a micro copter indoors but not enough range to fly a large copter. U need to show a 3D position with reflected altitude before any money for Vika III starts flowing.

It would cost $50 to build Vika III's airframe, hard wire it to Vika II's proto board to test motor control, but not fly. Then it would be $100 to build a SMT board with the last XBee, which could fly.
Posted by Jack Crossfire | Apr 16, 2009 @ 01:33 PM | 3,887 Views
Reynolds numbers 4 U

Not that anyone outside N. Korea ever listened to them, but we found the 2 aerodynamics lectures pretty useless. Don't think either the students or the speakers had a clue what the speakers were saying. Sounded like the shuttle didn't have any unique aerodynamic problems.

More sound resonance

Seeing huge drops with the tiniest smidgen of offset from 38khz. Such a sharp bandpass response is a crummy situation in the omnidirectional world.

Fortunately, your mortgage bailouts left us enough money for some Matsushitas. The Matsushitas R enormous 1"x1/3" devices & resonate at 24khz, so definitely more hope for range with the large airframe.

The amplifier degrades the radiated power from a Maxbotix.

The western bloc

In the western bloc, April 15 separates the men from the heroines. After inflation & tax increases, we now have less income than we did after finishing college but our boss made enough home equity since Tuesday to build an island.

The Goog loves to say "but outsourcing is lowering prices" & follow it with a mortgage advertisement, but if the price of labor in China rises 50%, is that deflation?
Posted by Jack Crossfire | Apr 15, 2009 @ 03:07 AM | 2,818 Views
Water rationing ended, so the golf course is back to full soaking during flying time. Fortunately, we know the soaking times better without water rationing. Water prices R going up yet again this month, to fund the wine baths at Goldman Sachs.


One other thing. The shuttle boosters have thrust vector control because of the slight chance the boosters won't burn out simultaneously. It probably could have flown every mission with main engine gimballing alone & saved 12 tons. The same 6 ton, leaky, flammable, hydrazine actuators from the shuttle R going into Orion.

If the diameter of the SRB's was determined by the width of railroad tracks, which was determined by the ruts from Roman chariots, which was determined by the width of 2 horse's asses, how did your government figure out the price of a house should be $1 million?

In other news, NASA reversed the idiotic votes of the public school kids of the 80's & named Node 3 "Tranquility" instead of Colbert. Calif* supreme court immediately overruled NASA's overruling, stating the LDS church unfairly manipulated NASA's minds & the module should really be named "Proposition 8".


The ping frequency resonates at 38khz instead of 40khz when sampled at 264khz. When sampled at lower rates, it resonated at 40khz. Since 264khz is the raw air pressure, U can assume the transducer resonates at 38khz & 40khz was the matched alias.
Posted by Jack Crossfire | Apr 14, 2009 @ 01:59 PM | 2,658 Views
Clearly from range testing different sample rates, we have good & bad samplerates but no dependance on higher bandwidth. Seems to be the resonant frequencies. Down to a few more commutes of different samplerates.

Next, your beloved 96Khz 24bit soundcard/oscilloscope died. Seems to be bad connections in the PCI slot & no-one makes 3.3V PCI slots for it anymore. Never used it for 6 channel sound after the first month. Never had time between commutes to do the connections & U can't hear anything in a dumpy $500 million apartment anyways.

Indeed, the last audio we did was in a time of 25 minute commutes. Then all U midwesters flooded in after your jobs got outsourced & the commutes went up to hours.

That got us thinking, U could probably make a really good 1Mhz 24 bit USB soundcard. If U wanted to make money on it, U could make it use VACUUM TUBES.

Indeed, people make USB vacuum tube sound cards all the time to convert between the DAC & the line level, but 1Mhz 24 bit is too crazy for the Goog.
Posted by Jack Crossfire | Apr 13, 2009 @ 06:49 PM | 2,858 Views
Hydrolics leak & are unreliable. Hydrolic fluid burns. Hydrolics require a turbine spinning at 82000 RPM & burning hydrazine monopropellant to compress a highly flammable fluid in a piston.

The shuttle used them because they had too many hydrolics experts on the payroll to switch to electric & electric actuators were unproven. Any cheap brushless motor from Align is more reliable than the hydrolic actuators on the shuttle, but like we said, it wasn't supposed to fly after 2010, before the extension.

They faced the same problem as any UAV hobbyist going for FAA approval. Mainly, how to get redundancy in case an actuator fails. Tandem pushrods didn't work because the broken one would act like a sponge. So the only redundancy is the 3 APU's.

That's like having a spare battery to power servos & why we minimized servos to just 1 of the most reliable ever made, the mighty Futaba S3102.

The APUs R the hydrolic compressors that were originally used on airplanes to control the pushrods in case of engine failure. They are not auxillary on the shuttle & a war was fought & lost to rename them.

They originally blew up like main engines because their airplane derived valves got too hot in a vacuum & ignited their hydrazine fuel. Their airplane derived sump pumps & oil pans didn't work in 0g. They rely on very tight tolerances between the gearing & the enclosure to scavenge oil.

test pilot notes

So the space shuttle has no redundant cooling system. It has 2 cooling systems & both R required to keep it from melting down. In space, it radiates heat from the payload bay doors. During takeoff & landing it boils off water. Sounds a lot like Hillary Clinton.

They used simulations for orbiter mode but had a test stand just like U for airplane mode. The shuttle was mounted on airbags that simulated the angular movements just like your apartment test stand. They spent a long time tuning feedback constants even after orbital flights started.
Posted by Jack Crossfire | Apr 13, 2009 @ 05:12 AM | 2,850 Views
Seems U need a lot more than 16 MIPS to get 450khz sampling so those $5 parts wouldn't fly. Fortunately, got it up to 260khz with a lot of assembly language tricks. Basically, accounting for every single clockcycle, unrolling the main loop, stripping the USB stack to the minimum, polling instead of interrupts, replacing subroutines with a big loop. The USB stack is down to 850 bytes.

Got analog crosstalk at 260khz, so it ended up taking nops to slow it down to 200khz. Some say it's worth building 2 USB devices at 260khz to see if sonar is feasable at all.

So with the nyquist now 50khz, the Maxbotix EZ-1 replaced with a bare transducer, only 2 dimensions being measured, the result was yet another incremental improvement but still worthless.

The next step would be repeating basic range tests at different sample rates.

Can't get good results unless your nyquist is several multiples of the ping frequency & we're only at a 50khz nyquist. Like a 44100 CD trying to generate a 14khz tone, sometimes the samples line up, sometimes they beat, & the beats make it sound grainy.
Posted by Jack Crossfire | Apr 11, 2009 @ 09:28 PM | 2,674 Views
Another set of batteries & sonar is definitely busted. Even with all the progress in omnidirectional sensing without propellers, with propellers & a large array, range was still a narrow cone directly above the array. The large airframe & the lack of accelerometers & magnetometers made positioning too sloppy to stay in the small cone. Altitude was nowhere close.

What happened with the array if single sensors had great range? Suspect the spacing in the array made every sensor have to look farther sideways. Another possibility is peripherals in the recycled Maxbotix EZ-1 interfering with the tone generation. Finally, there's the 30khz sampling creating aliases of propeller noise & destructive interference between aliases that wasn't there in 150khz sampling. A tone at 40 & 20 that didn't self destruct at 150khz would interfere at 30khz.

The best results were a pair of 13 second hovers directly over the array. Used really high gains & no altitude feedback. Almost had to flip it over to get feedback tight enough.

Your best chance with sonar is the smallest airframe possible or a blimp. Maybe an E-sky with SMT board. It would be a great replacement for an Evolution Robotics sensor if it was a ground vehicle or a blimp.

More likely you'll get another electronics upgrade. Sonar is that important 4 U.