Shop our Airplanes Products Drone Products Sales
Jack Crossfire's blog View Details
Posted by Jack Crossfire | Jul 14, 2009 @ 01:55 AM | 5,315 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 | 4,869 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 | 4,836 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 | 5,195 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
Posted by Jack Crossfire | Jul 08, 2009 @ 02:51 AM | 4,535 Views
This lens is so powerful, it can see back into the 80's.

Let's get 1 thing clear. It's a piece of junk compared to Canon lenses. It's blurry at 800mm & extremely blurry at 1600mm. At 18oz fully loaded, it's too heavy for the trapezoid mount.

The answer is no. The 2x teleconverter doesn't buy any more resolution. The fact that the 2x teleconverter has no front lens cap shows how valuable its manufacturer thinks it is.

What the 2x teleconverter buys U is sharper focusing. If your goal is focusing bright objects, use the 2x teleconverter & throw away 1/2 the frame to get better focus. It's much easier to focus this way.

It's probably no better than a 400mm L & it's probably no better than a 200mm L + 2x teleconverter for $200 in 2007. Unfortunately the Canon 2x teleconverter jumped 50% since then. It's definitely better than a 200mm L as shown by this award winning blog post.

F/8 is a really narrow depth of field. F/8 & F/16 R not a problem when using a tripod & a modern digital camera. The Canon's focusing squares R useless. It's too blurry & dark. Unfortunately, F/16 brings out all your sensor dirt.

U need to fabricate a lens platform to mount it on a tripod. It's too heavy to hang off the camera body.

Focus guides on T mount lenses R worthless because they always go on the bottom, but it still has a focus guide....Continue Reading
Posted by Jack Crossfire | Jul 07, 2009 @ 01:36 AM | 4,680 Views
debbie gibson someday (4 min 4 sec)

Here it is. A monster of a video from the lost corners of the 80's. Mashed a pristine audio track with the 2 crummy Goo Tube videos to get the best quality possible.

After throwing together a layout for the 915Mhz radios, it became quite clear that any standalone data radio would probably be too heavy for a Picco Z size spin copter. It would need to do the processing + radio on 1 chip. Would also have to use the Maxbotix transducer instead of the Matsushita to minimize weight.

Vika 1 will be 915Mhz & get a new ground station specifically for 915Mhz & sonar. 915Mhz will use SPI & no RS232. Vika 2 will stay 2.4Ghz. Moving the radio to SPI is a pretty big change. We start with the ground station. Just need a USB cable.
Posted by Jack Crossfire | Jul 06, 2009 @ 04:36 AM | 4,499 Views
VikaCopter uses a PID gain for autopilot & a PWM gain for all modes. If U max out the PID gain, U have to increase the PWM gain. PWM gain was low to make it easier for a human pilot, but the human had to go. Here we have the 4 camera angle & nose in orbit with effective rudder & stabilization.

rudder effectiveness regained (7 min 8 sec)

The answer is no. The Castle BEC has no reverse current protection, so we finally fried it. It has a fuse diode which doesn't seem to have been enough. Lineage power makes buck converters which make all BEC's obsolete.

Now 4 your 80's minute.

Low quality audio without dropout, higher quality video.
Deborah Gibson Someday (3 min 52 sec)
...Continue Reading
Posted by Jack Crossfire | Jul 05, 2009 @ 02:52 AM | 4,494 Views
U may have tried to erase it from your memory, but we did dream about a flying flag many years ago. Flew VikaCopter higher & higher with a flag attached until eventually it didn't come down & it reached orbit. Months passed and the orbiting flag became a routine fixture at night, filling more space than the moon. Over time it became more tattered & faded from view because of micrometeorites & entitlement programs....Continue Reading
Posted by Jack Crossfire | Jul 04, 2009 @ 11:33 AM | 4,692 Views
Underslung payloads 4 U (4 min 15 sec)

There it is. All flights have to take off pointing North & turn into the wind because of the 3DOF IMU. Managed to pull off some stiff wind without blowing string into the propellers....Continue Reading
Posted by Jack Crossfire | Jul 02, 2009 @ 01:40 AM | 4,497 Views
Obviously, if U want smooth orbits U need a dedicated orbit command & not 4 waypoints joined by curves. Probably the only way to do it is to have the computer look 1 waypoint ahead. Unfortunately, U can't read 1 waypoint ahead in a C program.

Pretty major software change, & reason to give U the long orbit footage with the current software to keep the blog alive.

pico C programs & wind (7 min 5 sec)

Some hovers demonstrating the latest SCP1000 tuning. Then some pico C programs: a nose-in orbit, nose-out orbit, & some laps. 3DOF IMU, GPS, & SCP1000 of course.

None of these programs move very fast in any wind. Changing heading while moving is real hard. The idea of a curved path & heading changes is pretty hopeless in any wind.

Now some stills 4 those of U who don't have day jobs to spend watching Goo Tube.
Posted by Jack Crossfire | Jul 01, 2009 @ 03:06 AM | 4,721 Views
Tri rotor's first daylight footage (4 min 26 sec)

Pretty tough wind but really clear air. The last time we flew a camera here was this award winning blog post almost 1 year ago.

Had yet to achieve the wealth & power required to etch tiny boards & the software was still 100% embedded.

Today, still don't have enough tail rotor authority to turn against the wind. Spent most of that footage banked over 30deg to stay in place. The 4 turn mission was more like a 2 turn mission. At least she's much more stable than the T-Rex.

TAIL ROTOR FAILURE (0 min 34 sec)
...Continue Reading
Posted by Jack Crossfire | Jun 30, 2009 @ 04:25 AM | 7,301 Views
Autonomous camcopter takes flight (0 min 37 sec)

There it is. The first video from Vika 1 with the tiny boards & DT700 motors. Finally got the automatic takeoff, turn, shoot, & land mission to work, but since it was dark, U get only 1 angle. Drew the battery all the way down to 9.3V. Who knows where the Super Simple ESC's shut off.

Magnetometer was useless because of the payload balancing requirement, but the ADXRS gyros pulled off a solid flight in 3DOF IMU mode.

Vika 1 in rate gyro mode with the SCP1000 is still the Jesus copter. The tiny board interferes less with GPS. Her magnetometer needs another calibration. Newer magnetometers advertise automatic degaussing, but the Micromag3 is free.

After spending 3 hours waiting for web pages to load, VicaCopter 4 is finally available for download. If U ever succeeded in downloading the source code & building your own VicaCopter, U still probably wouldn't know half of what she can do.

It's amazing after all these years, VicaCopter is still the only English language source code for a fully functional helicopter autopilot that you can download without paying for.

Still undecided about going for a micro tri rotor or another spin copter. Vika 2 has some more sonar algorithms ahead. An EDF based spin copter might work if the EDF can survive crash landings. All roads lead to moving the LCROSS budget up to July.
Posted by Jack Crossfire | Jun 29, 2009 @ 12:54 PM | 6,654 Views

Previous work on heading hold algorithms showed the commercial gyros U see on making snap turns probably don't use closed loops, but until yesterday, no-one knew if it was true or just our super low feedback rate.

When the pilot moves the stick, it bypasses the heading hold part & passes the stick directly to the servo. When the pilot releases the stick, the feedback loop regains control & locks whatever the new heading is.

There's no way a heading hold gyro based on totally closed loops would give the connected sensation an RC pilot wants. So what happens if U use a heading hold gyro for cyclic? The constant cyclic inputs all bypass the heading hold part, making it useless. For manual flight, a heading hold gyro for yaw would work, but in autopilot the yaw has constant inputs too.

Now U could convert the target orientation to microcontroller units & have the microcontroller track attitude in its own frame of reference directly. None of this could be easily converted to an embedded computer & the goal with ground based autopilot was easy porting back to embedded computers.

No, if U want 200Hz feedback, there's no way around a realtime embedded computer. Yet another myth busted.
Posted by Jack Crossfire | Jun 28, 2009 @ 08:22 PM | 6,712 Views
Heading hold mode takes flight (1 min 22 sec)

So this was heading hold mode on the airframe & full quaternion feedback on the ground in 105F weather. The ground computer commands cyclic at 50Hz to achieve a target attitude & the airborne computer commands cyclic again at 200Hz to achieve the desired change in attitude.

Unfortunately, there was too much lag between position feedback & attitude. The heading hold software isn't tuned for the optimum response. Any time U command changes in attitude instead of absolute attitude, you're heading for serious lag, but heading hold gyros can do snap turns so U still have a few more blog posts 2 go.

Vika 1 heading hold implementation (1 min 43 sec)
...Continue Reading
Posted by Jack Crossfire | Jun 27, 2009 @ 05:29 PM | 6,792 Views
Like a lost tribe worshipping a 40 year old plane wreck in the jungle,

every anti-US day, North Koreans gather around a rusted US spy ship they seized 41 years ago & chant some kind of hate speech. It makes U wonder what they worship on Ford Pinto day.

The answer is yes. N. Korea can get a nuke to Calif* & kill a lot of U. It doesn't need 2 B accurate. A missile hitting the remotest part of Calif* would wipe out a billion people. At least there R plenty of low paid flat broke programmers & unemployed missile defense workers they can hire.

The answer is no. They can't shower nukes on U. Long range missiles R going 2 B a once annual event because they don't have enough money to build any more. N. Korea's best move would be selling missiles to someone else, but Kim Ill the IIIrd doesn't want to be a mere peon for the Iatolla.
Posted by Jack Crossfire | Jun 26, 2009 @ 12:24 PM | 6,850 Views
So you're going to get heading hold on all the gyros with the 200Hz feedback, another round of test stand runs, probably another week before anything flies again. Now some notes.


Equilibrium tilt seems to work in a 3DOF IMU.

To make Vika 1 turn on a dime, she has a fixed neutral tilt hard coded for the body frame & changes a second, variable tilt in the world frame to respond to position. No matter where she's pointing, the variable world frame tilt is converted to body frame & added to the constant neutral body frame tilt to get the target attitude.

The variable tilt in world frame is contained in the integrals of the PID equations. Because we add the neutral body frame tilt after position feedback, the integral limits for position feedback don't need to encapsulate the neutral body frame tilt.

What happens in a 3DOF IMU where the current body frame tilt is constantly reset to 0? This IMU assumes whatever it senses is always the neutral body frame tilt after a reset. Instead of resetting to 0, you reset to the hard coded neutral body frame tilt.
Posted by Jack Crossfire | Jun 25, 2009 @ 12:26 PM | 6,959 Views
Originally VikaCopter had a small integral on the airframe to give her some heading stability. When rate feedback went to 200Hz, that went away.

Face it, ground based autopilot is no match for the copters with 200Hz onboard feedback. U only thought 50Hz was enough because used 25Hz. Given the need to fly in smaller spaces, maybe it's time to put orientation feedback back on the airframe.

The cheapest method is to stick with ground based autopilot & implement heading hold for all the gyros. While U debate that, how about another photo run.