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Jack Crossfire's blog
Archive for July, 2009
Posted by Jack Crossfire | Jul 27, 2009 @ 05:48 PM | 4,112 Views
Whew. Didn't know so many heroines lifted men with ease. They're all over Goo Tube if U search for "lift carry". U don't realize how easy it is for some of them & their positive attitude about it until U have the audio. Seeing what we envisioned 21 years ago in full audio & motion changes your view of men's position in the universe. Heroines lifting men may be more important than heroines walking on the moon.

Based on the number of heroines in U Know Where who R still in shape, the ratio of heroines to men in Calif*, & the puritan conservativism in U Know Where, don't expect any heroines lifting men on this blog. However, our conniving brain is hacking on ways to do it along with the anti gravity problem & the fusion problem.
Posted by Jack Crossfire | Jul 26, 2009 @ 10:00 PM | 4,176 Views
That's right kids. We gave tethered transmitters a chance & they failed.

Nylon wheels R too noisy. Locking them is more pain than it's worth. Glitches came back in the outdoor environment. Never had any luck with long, unshielded cables in the field. Tethered transmitter was a nightmare, constantly getting tangled in the dark.

Electroluminescent wire

is something which came out of nowhere in the last 10 years. Unlike LED's, it burns out after several thousand hours. Look at all the stuff we didn't have in the web 1.0 boom.

When we were kids, we got some wires that glowed dimly in the dark after being exposed to light & went crazy over them. Then we had a college buddy who bought a neon sign & smashed it. When we built HeroineClock, the only affordable options were LED's & incandescent lights. Then in 2006, people started putting super expensive light emitting wire on their copters. Now, apparently EL wire is dirt cheap & everyone's got it in China.

It definitely puts VikaCopter's scavenged LEDs to shame.
Posted by Jack Crossfire | Jul 25, 2009 @ 10:45 PM | 4,604 Views
We haven't used a camera shutter pin since 2007. Vika 1 showed all that business of camera shutter modes & timing shutter events is a waste. You're better off getting it continuously shooting before takeoff & shooting the entire time. Why risk losing the shot because something wasn't configured to go off at the moment of truth?

The only time we used shutter pins was the extremely crummy pencam which needed 1 pulse every 10 seconds & didn't have continuous shooting mode. It's as heavy as the A560 with buck converter. New cameras record hours & hours of video.

The only use of a shutter pin would be very long exposures where U held attitude constant for the exposure, but that's not very feasible on Vika 1.

Dobson test shots

The first test shots with the Dobson show it's a huge improvement over a tripod. No wobbling. Final glitches removed, it now has very precise aiming. Light enough to carry up & down stairs. No need to lock the wheels. The most precise aiming comes from tapping the stick. Definitely need bungies to transport the gear. Remove camera before transport, in case it runs off the road.

U know, it probably could have been a lot smaller with precision machine tooling.

Timelapse motion control requires removing the accelerometer & magnetometer from Vika 1, which requires opening the IMU, which requires the rework for 900mhz.
Posted by Jack Crossfire | Jul 25, 2009 @ 05:52 AM | 4,247 Views
4 those of U still with jobs/current Calif* residents, have some flyovers.

Wed Jul 22/09:27 PM 12 above N 11 above ENE
Sat Jul 25/09:07 PM 29 above NNW 14 above ESE
Sun Jul 26/09:31 PM 27 above W 20 above SSE
Tue Jul 28/08:46 PM 36 above SW 10 above SSE


Rise of the gyro compasses

U need to determine true North. U make lots of magnetic fields. Wind makes GPS heading unreliable. U need to fly for hours & hours. U need a gyrocompass. Gyrocompasses sense the rotation of the Earth to determine true North. In an IMU, the rotation shows up as a 90' rotation over 6 hours. That's right. If U left a super accurate IMU on a table for 6 hours & it was calibrated for true 0 rate, it would show a 90' turn. It can use this rotation to correct the heading over many hours.

By default, the 0 rate on a typical ADXRS610 is always calibrated 0.00004V off because of the Earth's rotation.
Posted by Jack Crossfire | Jul 24, 2009 @ 01:25 PM | 4,966 Views
Got PPM to a decent level. Still a lot of glitches. Decided to get as much fabrication done as possible & get U some video of the dobson in action before the next commute.

Motorized Dobsonian mount (1 min 35 sec)


If the counterweight looks familiar, that's because

http://www.rcgroups.com/forums/showthread.php?t=984892

It's the landing gear from the pentarotor.

Camera gimbal dreams

The motorized dobson mount made us think more about camera gimbals.

U could probably do a gimbal with 2 of the tiniest servos & the same friction drive mechanism. Instead of directly tracking an attitude, it would only damp motion, relying on hall effect sensors to maintain an average, fixed orientation. The average orientation would be controlled by manually bypassing the loop & resetting the target hall effect values.

Systems that track attitude with servos have been disappointing. The best systems use video tracking, but moving analog video into a computer is super expensive.


DIY servo control dreams

Instead of sending PWM to the yaw servo, you're better off capturing the servo potentiometer directly & controlling the motor with the main computer. That's right. Completely custom servo control just like Heroinesapien. That's how U get virtual flybars on T-Rexes.

Except for an indoor tri-rotor where the servo is really small & basic, the large tri rotor is stable enough to not need any servo hacking. It has enough yaw inertia to fly manually with no damping of any kind.
Posted by Jack Crossfire | Jul 23, 2009 @ 12:20 PM | 4,320 Views
Another commute & it became quite clear we're not going to have a motorized dobson in time for the shuttle/station pass. The MOSFET H bridges interfere with the PPM. To get PPM out of any transmitter, U need amplification.

Servos stall below a minimum RPM as expected & can't go very slow. They can't handle the full 12V of the MOSFETs, so U need to limit the PWM. At least the MOSFETs haven't burned out yet, like they always used to do.

That's 1 commute to get PPM to work, 1 commute to finish structural work, 1 commute for the first field test. How about some news.

THE TRUTH ABOUT CHINA

China is going to forgive US's debt. That's right kids. The central bank of China is going to tell Chinese savers "Sorry suckers. Your money's gone, but it beat unemployment for the last 100 years.". They're going to devalue Yuans to 0, create a new currency, & a big chunk of the world population is going to die off. That's how the world works.

Consider that to get $200 billion in trade surpluses, China now has to buy $500 billion in bonds. That's their commitment to 100% employment overshadowing all desire to make money. The world economy is really China giving everyone money & everyone buying Chinese stuff.

Maybe U thought times changed since ancient Egypt, but slavery has always been fundamental for humans. Fortunately US is now on the receiving end of slave output. Chinese enslave themselves to US to fill their biologically...Continue Reading
Posted by Jack Crossfire | Jul 22, 2009 @ 12:55 PM | 4,866 Views
Even with our draconian component scavenging & reuse, the dobson mount is already up to $58.12. The wood is completely stock we got 5 years ago. The MOSFETS R all from CRT's & 20 year old hard drives. Diodes came from burned out power supplies. The microprocessor is from our strategic free sample stockpile from 5 years ago. The oscillator is from Heroine2200's spare parts 8 years ago.

Our first 9 years of H bridges have been extremely inefficient BJT monsters, using op-amps to boost base voltages. They were cheap & simple. They never burned out. In the interest of dumping op-amps, we now have MOSFET H bridges on the dobson. They're very complicated & expensive. They need reverse current protection diodes. They're very efficient....Continue Reading
Posted by Jack Crossfire | Jul 21, 2009 @ 12:05 PM | 4,349 Views
India is going to make July 20 a national holiday. That's right kids. The Apollo program is that important to them. They all worked on aerospace & only came here to work on cat mortgaging software because of the free houses.

US won't make the moon landing a holiday obviously, but it may make October 4, 2018 a national holiday. That's when universal healthcare gets bailed out.

Now a repeat of our Apollo videos 4 those of U who didn't get the memo.

neil armstrong reborn (2 min 57 sec)


NASA said these were restored segments from the 1969 broadcast, but we can't see any difference compared to the other Goo Tube uploads.

...Continue Reading
Posted by Jack Crossfire | Jul 18, 2009 @ 01:32 AM | 4,462 Views
The answer is no. U can't drive a 915Mhz front end using a USART. U can't change clock polarity as required for fake full duplex. So even with a dirt cheap, bare front end, the options for 915Mhz R expensive & more expensive.

Radio breakout boards would now be the same size, have the same hardware & cost as much as completely new autopilot boards. Having the radio on the same board as the autopilot would greatly increase bandwidth. Switching between 2.4Ghz & 915Mhz would involve switching the entire autopilot. U can devote the accelerometer & magnetometer pins to the radio.

Groundstation is probably better off with a breakout board, but want to maximize the bandwidth.

There R now a bunch of processors which can probably make spin copter a reality & greatly reduce the cost of a VikaCopter.

915Mhz Vika1 airframe:
PIC18F23K20 28 pin $2.40

915Mhz Vika2 & Vika3 airframe:
PIC18F13K50 20 pin $2.42

915Mhz groundstation with sonar:
PIC18F14K50 768 bytes RAM $2.66

Everything U order has to come with backups, so the $9 in Vika 1 really killed us.

But U don't know if 915Mhz will work with GPS & the Walmart video transmitter. It may be a complete disaster, which has U leaning towards another basic, through hole test setup.
Posted by Jack Crossfire | Jul 17, 2009 @ 04:53 AM | 4,234 Views
So U think you're going to be the last American when everyone flees to China.

You're going to have all the roads to yourself & drive around at 200mph. You're going to loot all the stores & make yourself a solar powered Winnebego.

But realistically, all the stores in US sell are mortgages. Forget about any electronic parts without global shipping & who's going to bother shipping to 1 person? The roads are going to disintegrate long before U get your fling. So who is captain America gonna be?

The last American is probably going to be someone who never did anything they were told, never got a PhD, saw themself as their own provider, saved gold instead of dollars, avoided professional advancement, never got a Palm Pilot/iPod/Razr/iPhone/gPhone/netbook, knows how to vacuum pack food in glass jars & make their own fry sauce.
Posted by Jack Crossfire | Jul 16, 2009 @ 02:25 AM | 4,445 Views
It was sunny in Fl*rida but raining foam in the upper atmosphere.

Shedding on sts-127 (0 min 18 sec)


We expected the 6 tank refills to make quite a shedding & sure enough, the tank shed like a snowstorm. NASA predictably insisted foam shedding was not a problem, the debris looked doubled because of shadows, & it only caused small scuffs.

The voters predictably did exactly what they were told & shut up.

http://forum.nasaspaceflight.com/ind...opic=17825.525

Oh yeah. NASA tested it to 6 thermal cycles without seeing any shedding. Didn't U get the memo about those tests? Why wouldn't NASA be perfect?

The smallest copter in the world was the

http://www.proxflyer.com

It flew for 30 seconds on a charge. 4 years after the Wowwee flytech, ornithopters R a no brainer. People build insect sized ornithopters all the time. U might as well go for something bigger & longer flying.

The mane problem with shrinking a tri rotor by overlapping blades is blades hitting shafts in a crash. With EDF40's, U need a lot more room for the ducts & they're real expensive to crash. The smallest tri rotor would be 7".

Any spin copter would be brushed, over 5", & use a custom 900Mhz radio on the same board.
Posted by Jack Crossfire | Jul 14, 2009 @ 11:43 PM | 4,515 Views
Getting a direct radio interface + flight computer out of a $3 microcontroller is not easy. Those 915Mhz front ends need full duplex SPI. U'd need some diabolical analog circuitry. U can afford a much more substantial microcontroller since you're dropping the $45 for an Xbee. Going with the analog solution lets U keep the existing XBee support. 915Mhz probably has shorter range, so U want to keep the XBees around. Despite the analog circuit, neither solution is any easier in the software.

The good news is the USB bit banger works. We can program & verify a PIC without a bootloader & in a humane amount of time. The advantage to running without a bootloader is of course, faster interrupts & less software to get working on every board.

The trick with the bit banger is U need to write 31 samples before U can read the 1st sample value. The workaround is to only set input enable when U intend to read & during the read pass, skip to the 1st input enable bit.
Posted by Jack Crossfire | Jul 14, 2009 @ 01:55 AM | 4,367 Views
It's cheaper than any purpose built BEC. It does work. It gets hot when converting 12V to 3.3V for a digicam, so no shrink wrapping. It's designed to be soldered on a board like a BGA, with airflow under the inductor. It needs odd resistors to determine the output voltage & can't use resistor dividers like the LM317. Sparkfun doesn't have the odd resistors, but digikey does, in addition to having the DC-DC converter.
Posted by Jack Crossfire | Jul 11, 2009 @ 10:08 PM | 3,915 Views
So many of U flood the blogs on weekends, writing blogs on weekends is almost as much of a waste of time as writing them on weekdays.

The reason Calif* is getting rain in July is Mt Sarychev. Ash plumes in the East Pacific always bring cold, rainy Summers to Calif*.
Posted by Jack Crossfire | Jul 10, 2009 @ 12:27 PM | 3,867 Views
LCROSS is heading towards a very large, motorized, Dobson mount, which can be bolted together in the field & stored for a human amount of rent. The mane problem is finding suitable bearings.

There it is. Our 2nd USB gadget is the bitbanger. It converts USB to 7 logic signals. Its purpose is a universal PIC, Atmel, JTAG programmer. For the PIC, U need a glue circuit to get 9V. For Atmel, U need a bag of resistors to lower the voltage.

We've been using the parallel port programmer since 2005. After 1 year banging on TTL chips, 3 years banging on 68HC11's, our first PIC gadget was HeroineClock using a PIC16f877. It now grinds away for 10 minutes on VikaCopter's firmware & more gadget needs keep coming.

Most of U implement USB or XBee bootloaders. With the number of gadgets & different communication methods we're using, that would mean implementing a new bootloader for every gadget....Continue Reading
Posted by Jack Crossfire | Jul 09, 2009 @ 01:47 PM | 4,168 Views
As U celebrate National Geriatrics Day, think about this.

U've outlived Karen Carpenter, Kurt Cobain, Brandon Lee, Heath Ledger, River Phoenix, John Belushi, & Chris Farley. They were all flat broke, account balance 0, & nobody by your age. Stick that on your scalp & grow it.

Now from the blog file, it's

How to win at red light cameras

Green lights R timed so everyone next to the solid white line when the light turns green can get across. At least in Fl*rida, yellow lights R timed so if you're going at the speed limit & you're in the solid white line, you'll make it. It's probably 1/2 the white line in bankrupt Calif*.

If the light is green when you're before the white line, slow down as U approach the white line. If it's still green when you're at the white line, floor it & keep going as fast as possible if it turns yellow. If you're behind someone real slow, get right up against their bumper so the cameras can't see your license plate. Don't worry about rear ending people. It's cheaper than a red light fine.

The whole idea with the cameras is to increase rear end collisions & create demand for higher medicare taxes which can then be diverted to mortgage bailouts.

Now some 1600mm shots....Continue Reading