Jack Crossfire's blog View Details
Posted by Jack Crossfire | Jun 24, 2009 @ 03:46 AM | 6,742 Views
U know, we don't have a clue what causes most sonar clocking anomalies. They're affected by the value of SONAR_HISTORY.

So in our efforts to shrink the useful flying space to dumpy apartment size, we have a 1ft array. Sonar can certainly detect the copter below 2m but can't keep her in an apartment sized box. Takeoffs R still out of control. Suspect the large airframe has too much inertia & a micro copter might do a better job.

Tried some circuits & it was pretty bad. Without a full 9DOF AHRS & with that confined space, U can't match Vika 1.

So how did microdrones.com get those super tight videos of the nerdy guy pushing the copter? He's got a super expensive RTK GPS system, the airframe is smaller than Vika 2, it's got a full 9DOF AHRS, it's super balanced to not require as much lowpass filtering, & of course super fast feedback on the airframe....Continue Reading
Posted by Jack Crossfire | Jun 23, 2009 @ 12:48 PM | 6,946 Views
As you've probably gathered, an autonomous copter doesn't give U much more pilot bandwidth than a manual copter. If 1 person had to fly one of the commercial UAV's with the super complicated ground stations, how much information would they really get from the ground station? Normally, U have a spotter outside shivering while someone else stares at the screen in a van.

Extremely stable weather in the last 48 hours gave U some extremely good sonar performance. Got some attempts at equilibrium tilt with the 3DOF IMU. It's questionable at best. No other issues with the IMU. Pushed the sonar range again.

You've got a 2x2 meter box at 4m of altitude where sonar is most reliable.

Running PICOC in a fork paid off. Had crashes from the return; keyword not being implemented but the copter didn't...Continue Reading
Posted by Jack Crossfire | Jun 22, 2009 @ 01:32 PM | 6,624 Views
So the oscillations were the sonar clock drift & nothing sinister with 3DOF IMU's. The LISY300AL is indeed more stable than the IDG300. It's not an ADXRS613, mind U.

2 days of hard sonar debugging & she's triple bingo again with the tiny board. Working around clock jitter by checking the ground station & rebooting if it's out of limits, just like we do with the battery, gyros, radios, landing gear, servo, ESC's, propellers, & rubber bands.

PICOC isn't reliable enough to run in a thread. Got PICOC running in a fork instead of a thread & flying a few successful missions from takeoff to landing. Equilibrium tilt for 3DOF IMU's would be nice. U also need takeoff & landing ground station status.

Horizontal range seems to be +/-2m at 8m of altitude. Vertical range is 6-12m. Not sure it would be any better indoors with a micro copter.

Got 8 minutes out of the 4Ah & 7m30s out of the oldest 3.3Ah, so there's a minor improvement from the tiny boards.


The schematic for a home made ESC is here.


Home made ESC's would be nice. Doubt we can get them any smaller than the Castle 9. Combining the ESC's & computer on 1 board may pay off with the indoor copter.

They would allow collecting RPM & current data, which no ESC can do. RPM knowledge would eliminate the hacks for different batteries.

Designing an ESC seems to be pretty simple. Power 1 of 3 circuits at a time with a P & N mosfet. Wait for open circuit voltage on the next circuit to rise above the average voltage. Switch to the next circuit. Shut down if current exceeds a limit.
Posted by Jack Crossfire | Jun 22, 2009 @ 12:37 AM | 6,628 Views
The average RCGroups blog poster lasts 2 years. Most of the content in the Blogs is the same. Human activity doesn't vary much. With less money in circulation & more in treasury notes, there's much less happening in the world.

The internet is a lot slower than it was in 2006. 1 minute page loads R now considered fast on Sunday evening & business hours.


Make the space shuttle fly as low & slow as possible to get a given payload into orbit with the maximum fuel load. For lighter payloads, fly shallower. For heavier payloads, fly steeper. Base maximum payload on the steepest trajectory U can safely abort from, not the amount of fuel.

U want to make it as easy as possible to abort & always drain the tank completely regardless of the payload. Even hauling a feather should drain the tank completely. Any extra fuel means U risked the astronaut's lives needlessly.


Have some pretty serious clocking errors with the tiny boards. Another hand tuning of crystal frequencies for that one, but the jitter problem continues. It may require a hardware solution if USB isn't realtime enough. It takes a lot of tweeking to tune each sonar system.
Posted by Jack Crossfire | Jun 19, 2009 @ 11:31 PM | 6,213 Views

Java was slow. Keystrokes lagged. U couldn't remember the keypresses to navigate the menus. It took a lot of power to render the GUI. The artificial horizon was pretty bad in flight. It took too long to decipher information on it. That had everyone looking at a text interface.

Most people cram a bunch of traditional airplane instruments in a window. How well does that work on a phone? How would U send PICOC commands to the vehicle?

Most important factoids:

gps satellites/sonar SPL
thrust balance
2.4Ghz bitrate
72Mhz bitrate

Not exactly what Goog spits out, but personal experience. Easy to get on a command line, but we want extra optional factoids like gyro bias. Graph format data would be nice. Maybe an EKG machine, because what you're doing is monitoring health & not flying anything. When we're out working, it's easier to navigate with a keyboard than a touch pad.

Wish list:
Easily readable fonts.
White on black for daylight.
Make voltage, GPS satellites, & thrust balance big enough to see from far away.
Graph & numeric options for each factoid.
Automatically partition based on enabled graphs.
Bingo board for IMU state.
Posted by Jack Crossfire | Jun 19, 2009 @ 12:04 PM | 6,028 Views
Payload & engine performance is mostly constant. Sensors capable of detecting the first few feet of altitude R heavy, expensive, & unreliable. It takes a lot of fuel & time to hunt for equilibrium thrust. An adaptive takeoff algorithm gets U on North Korean headlines, but all roads lead to hard coding.

Rocket launches R hard coded. Put the SSME at 104% & go. John Carmack was the first to use a carefully tuned PID controller & burn a lot of fuel to take off. For some reason, rocket hobbyists all copied him.

Maybe we've gotten jaded about physics. Went from a totally adaptive vision to over 200 parameters in configuration files. Some of it is configuring your own GPS system.


Now for the first time ever, it's a graph of neutral pitch vs. neutral yaw on the same IMU. They're coming out consistent on the same day, but not days apart. Suspect there R mechanical instabilities in the gyros which keep any temperature table from getting the last bit of gyro bias. Since we're using another gyro as the thermometer, it squares the error from mechanical instability.

Yaw bias from pitch bias is busted yet again, but hopefully we still can get yaw bias from position, the most cooly deadly looking a piece of calculation as ever U have laid eyes on.


Sonar is killing the budget. It requires flying low & fast over a sea of electronics & quickly damaging something after only a few minutes every commute....Continue Reading
Posted by Jack Crossfire | Jun 18, 2009 @ 12:52 PM | 6,251 Views
Using pitch & roll drift to estimate the yaw drift is a myth you've been busting for years. It didn't work with the IDG300, but that was a much bigger package.

Let's blast the IMU with the heat gun & see what happens. If the temperature changes slowly enough to keep them all matched, U can probably derive yaw drift from tilt drift. In flight, they emit different amounts of heat, they're blasted by prop wash & their heat capacities differ.

If U get tired of reading about 3DOF IMU's, U can give up & install an AK8976A from www.asahi-kasei.co.jp. That's a 3 axis magnetometer & 3 axis accelerometer on 1 chip.

Unfortunately, those single chip 6DOF deals R exclusively for phone companies like Apple. You're stuck with an HMC5843 for $20 & an ADXL320 for $8. That would double the IMU tag.


For Vika 2 automatic takeoff & landing, U don't have a position signal until a minimum altitude is reached & U can't tell when the minimum altitude is reached without a position signal. Ramp collective & fix attitude, hoping the sonar field catches it above a certain level before it flies away. Get the starting position when minimum sonar amplitude is reached & engage position hold.
Posted by Jack Crossfire | Jun 17, 2009 @ 12:29 PM | 6,313 Views
2 days on the Blog page. Either U people R too focused on your day jobs or The Goog changed its algorithm.

Ghetto blimp

Another idea is ghetto blimp. Instead of those gigantic envelopes U multi billion dollar home owers stuff away in your 1,000 sq ft mansions, ghetto blimp would be an 11" party balloon. It would offset some of the weight of the computer, sonar, & Xbee. The electronics + $20 Walmart power system would hang under it & it would spin around like spin copter. It would use the same throttle phasing & unbalanced payload to get translation, but solve the weight problem with heleman.

It would be completely impractical, but it would prove indoor sonar flight & eliminate the risk of spin copter.

The minimal sonar autopilot is coming in at 10g. The balloon reduces it to 5g. U could probably get the autopilot to 5g by using a 900Mhz radio chip, no sonar amplifier, & eliminating the Walmart computer.

Unfortunately, any time U introduce blimps, it turns into a toy.

Atmel vs Microchip 900Mhz

fully powered antenna output
smaller package

needs RF choked antenna power
bigger package
not at digikey

Everything from Atmel is newer. We would interface the chips with SPI & forget about extra microcontrollers. Probably couldn't fit GPS in Vika 2's RAM with that method.

More Vika 2 4 U

Whew. Vika 2 is definitely a crash prone wreck. The Super Cheap ESC's don't cut off. She's too...Continue Reading
Posted by Jack Crossfire | Jun 16, 2009 @ 03:24 AM | 6,843 Views
So there's no way to get the full power out of Super Cheap ESC's if there's any noise in the PWM at all. 1 glitch over the maximum pushes the automatic throttle calibration lower & causes U to have not enough power. To get maximum power out of the Super Cheap, U need PWM with no noise or ESC's that allow fixed throttle range.

Worked around noise on Vika 1 by having extra PWM table entries, but took the entries out for spin copter, then ported spin copter back to Vika 2 & it didn't work. U need the extra table entries.

> West winds 10 to 20 mph...becoming 5 to 10 mph after midnight.

Your government still labors under the delusion that cold fronts bring lighter winds. Sonar guidance got another attempt in the wind anyway.

4 today's movie, John Carmack had another hit with Human vs. Rocket. Man with balls of steel pulls Methane/LOX rocket.

Human vs. Rocket (2 min 38 sec)

Posted by Jack Crossfire | Jun 14, 2009 @ 05:33 AM | 5,245 Views
Now that you're $90 bankrupt on etching, there's no need to use XBees anymore. The XBee is the weight limiting part for spin copter. U can get bare XBee chips for $3. No UART, only SPI. Indeed, you'd need your own radio for any commercially viable UAV.

For 900Mhz you'd now skip the XBeePRO 900 & build your own out of an MRF49XA & a bag of parts. 7dBm output power compared to 17dBm for the XBee. With the $200 still blown on 2.4Ghz video, upgrading at least 1 copter to 900Mhz radios is a good idea.

Weight comparison:
Bare through hole Vika 1: 3.8oz
Surface mount Vika 1 with dongles: 1oz

Mind U, extra voltage regulators R required for lighting & GPS on the SMT board.

Wish list:
2 scratch built 900Mhz modules
Switchable 900Mhz ground station mode
$20 spin copter test
Mirror lens
Posted by Jack Crossfire | Jun 13, 2009 @ 03:49 AM | 5,340 Views
Whew. That was murder. No way this would ever be economically viable. You're definitely better off from a weight, size, & cost standpoint to have every sensor on the board. Our $parkfun breakout board collection doesn't leave many options in that regard. Built 3 autopilots with those & they're always a mess.

Someone still had to discover it was a mess & that's what the Jack Crossfire blog is 4.
Posted by Jack Crossfire | Jun 11, 2009 @ 12:33 PM | 5,309 Views
Going over the Walmart specials again, a spin copter would take buying lots of toy copters & finding out if any have enough power. There's no other way. $100 was the price of finding out 12mm brushless motors R too heavy to land.

The Havoc Cyclone looks like it might work if chopped up. Lift junk hardware first. Etch a single sided board with no voltage regulator. Single sided is lighter than double sided. That's July's budget.

Our double sided boards cost 2x as much & weigh 2x as much because they need 2x the etching board & the vias R too big. Their only advantage is the form factor & the wow factor for our Iranian readers.

SSME nugget 4 U

The answer is yes, the SSME has 1000 tiny tubes on the inside of the nozzle, not the hatbands U see on all the media photos. The outside rings R called hatbands & just keep it from falling apart. Didn't know this, so didn't get a high resolution photo of the tubes. Only got a wide angle photo of the nozzle.

The tubes R 1/4" in diameter on the aft end & shrink to pin size as they approach the forward end. Liquid hydrogen flows from the aft end to the forward end to keep the nozzle from melting. The tubes R braze welded to the nozzle wall. Finding leaks is real hard.
Posted by Jack Crossfire | Jun 10, 2009 @ 03:30 AM | 3,231 Views
The answer is yes, etched boards can fly a copter. Her only major problem is a nasty throttle falloff which happens between every ESC reboot. It doesn't matter what max throttle is set to. The only explanations R PWM glitching high, rate damping not clamped.

In case U don't know what standby power on a sonar guided copter is for, the IDG300's normally don't initialize properly, so once U get them going, U need to keep them on. The IDG300's also put out a lot of heat, so it stabilizes the IMU temperature.

Flying on sonar again is a perfect time to remember Jim Anglesey who died of Leukemia in 2005. We wouldn't know as much about audio if it wasn't for Jim. We would know something, but the whole sonar navigation idea may not have happened. So when you're watching Vikacopter flying by soundwave sensing, there's a bit of Anglesey in there.
Posted by Jack Crossfire | Jun 09, 2009 @ 04:19 AM | 3,240 Views
The answer is yes. U can etch a PCI card if U have enough money & R obsessed enough. There's a pale fat guy in Thousand Oaks who probably did it. Not sure what U would do on PCI anymore. It's not portable enough for videography. No video U get in the apartment is uncompressed.

Board etching would allow sonar samplerates in the 500khz range instead of the current 180khz. Not sure there's any more data to extract from the transducers.

Future Vikacopter autopilots will be double sided. Vika 2 will get extra 12V pads. Standby power is a mess because of the lighting. The solution is to power lighting from the main plug instead of the autopilot pads. Main diode can't handle the Vika 2 load either.

gEDA can do double sided components. The trick is to toggle the "far side" layer before picking components from the library. They're always placed face up on whatever side is visible.

It's day 3 of Vika 2 configuration but month #3 of sustained 20mph winds in the midnight hours.

The IMU needs more padding & another round of rate damping configuration. That's why we don't mount them on main boards, U all in one freaks.

Choked up tail horn seems to be a disaster. Go back to outer hole & throw in more right rudder.

Throttle range needs calibration.

Nose mounted sonar is getting destroyed by landings but range seems improved.
Posted by Jack Crossfire | Jun 08, 2009 @ 12:05 AM | 3,614 Views
So the board gets too hot with the padding. U couldn't have the IMU on the same board. The PIC locks up again. PWM doesn't work again. U need a full radio test. All the telemetry is coming in at least.

Every time U build a new computer, U think it can fly in 1 day when in reality 40,000 lines of code & dozens of systems have to be calibrated & work perfectly.
Posted by Jack Crossfire | Jun 06, 2009 @ 04:43 AM | 3,325 Views
Just when U thought U had a temporary through hole aircraft to fill the blog posts from now until Monday, the miniature parts arrive early. So that means you're ripping up yesterday's work & installing new electronics again.

Now look at the damage:

4 gyros: $53.92
More fleet upgrade parts: $66.74
Gyro & fleet upgrade parts: $44.21

That's surface mount commitment.

Now the etching consumables:

Etch board #2 & flux remover: $21.93
Transparencies: $32.76
FeCl: $10.96
Draino: $6
Etch board #1: $13.16
Black light disaster: $5.67

$255.35 in total for fleet modernization & Vika3. It better have an advantage over any Arduino or gyro breakout board U could buy.

Arduinos: 3 * $33.95
LISY300AL board: $30
IDG500 board (1x1 in): $75
No-one sells a 3D sonar board yet.

The IDG500 board doesn't meet the size requirement for Vika 3. This number doesn't include tax & shipping. We're probably breaking even by etching.