Shop our Airplanes Products Shop our Surface Products
Jack Crossfire's blog View Details
Posted by Jack Crossfire | Mar 06, 2009 @ 01:22 PM | 2,826 Views
Ghetto GPS didn't work on the airframe. Never got a thing in the field, with all other systems disabled, at 100ft AGL, or any of that other stuff. The latest theory is foam touching our beloved upside down pins.

No problem flying ghetto rotor manually, using IDG300's. Just barely enough power to go up, even with the new motor mounts. Slightly tail heavy according to the PWM recording. Ghetto LEDs were probably visible enough.

Now lets get one thing perfectly clear, for everything U know & everything U've done, there are millions of people who know & do the same thing. In a planet of 7 billion people, it can't not happen. They don't all show it on the internet. Even fewer get on The Goog.

There are millions of people with the skills to put VicaCopters together, millions of UAV's of 1 kind or another in the world, & thousands of autonomous tri rotors. There are more UAV's than all the full time soldiers in the world. A world war fought purely by the current UAV fleet would be broader than anything humans could pull off.

1 autonomous tri rotor is produced somewhere in the world by 1 Jack Crossfire every day. All the defense contractors & hobbyists of the world produce at least 1 UAV every second.

Compared to the human birth rate of 2.5/second, humans have probably 2 years before their birthrate is outstripped by UAV's. In 30 years, humans can expect to be outnumbered in total number by UAV's.
Posted by Jack Crossfire | Mar 05, 2009 @ 03:19 AM | 2,786 Views
Got a sheet of copper in the mail last year but only figured out a use 4 it recently. It's now the ground plane of our uBlox 4 ghetto GPS module. The tri rotors don't have enough flight time to lift the Altoids, so it was time to give passive antennas another try.

The passive antenna mounted right above the module actually worked when connected directly to a PC. Now that old uBlox4 was a better investment than AIG.

Does ghetto blox receive anything fully integrated on the airframe? Fuggedaboutit. We have a few more commutes to go with this one.
Posted by Jack Crossfire | Mar 04, 2009 @ 05:12 PM | 2,524 Views
For all your heroine worshipping, it's time U faced facts. Heroines caused great depression II.

In the old days, the media called heroines investing geniuses because they were experts in housing, the CEO of the house. They knew all the housing & domestication stocks & those stocks were doing great. Their stereotypical credit card charging made them richer through the power of housing inflation.

Where are the CNN stories praising heroines for their domesticated genius now? When the unlimited credit disappeared, the CEO of the house was yet another bimbo with a stack of credit cards.

CEO of the house before. Now CEO of the depression. The mortgage bailouts are bailouts for heroines.

Men wanted gadgets. Heroines wanted real estate. How many of your heroine coworkers bragged about how they made their husbands buy a house instead of a model copter back in 2005? The depreciation on average Bakersfield mansions would cover 300 model copters, if taxpayers weren't covering it.

The fact is if heroines thought more like men & wanted gadgets instead of kitchen remodelling, Micron wouldn't have laid off all of Idaho. We'd probably have humans exploring Mars instead of plunging their total economic output into mortgage bailouts.

Heroines caused great depression II (0 min 40 sec)

Posted by Jack Crossfire | Mar 04, 2009 @ 01:02 PM | 2,685 Views
The DT700's R real bricks. Don't be surprised if these bricks don't fly for very long on the current batteries. The battery budget of course went to higher income tax so U could get more equity out of your tree houses, but don't bother selling those tree houses to US. We're sucked dry by higher taxes....Continue Reading
Posted by Jack Crossfire | Mar 03, 2009 @ 02:10 PM | 2,653 Views
There it is. Vika II. She does indeed fly. Can only go 1ft off the dumpy apartment floor until we get a break in the weather. That's not predicted for yet another week. Meanwhile, it's full speed ahead between commutes on upgrading Vika I's propulsion, installing Vika II's GPS, implementing GPS -> heading corrections....Continue Reading
Posted by Jack Crossfire | Mar 02, 2009 @ 12:48 PM | 3,475 Views
No-one is doing PC soundcard sonar, but we feel it's the next step 4 U. There's no way analog circuits & microprocessors R going to do the job. We don't know enough about the ambient noise in audible frequencies to filter it. Some quality time with a PC soundcard can show U exactly what can be extracted from audible noise & how to extract it before investing any more in sonar.

Still think 3D sonar is going to be a good tool because humans have been doing it for years. Humans can filter out ambient noise & localize objects in 3 dimensions. 3 humans could probably fly a copter blindfolded if U got each human aligned in 1 axis. Maybe we should get some Slave 1-B's from India instead of sonar transducers.
Posted by Jack Crossfire | Mar 02, 2009 @ 02:18 AM | 2,669 Views
DVD+R DL doesn't work & it's slightly more expensive than hard drives if it works. You're lucky to get 2 good disks in a pack of 25. A blu-ray burner would be $200. 1TB of Blu-ray media alone is another $200. This is yet another Sony fanboy product. Sony turns $400 into $200.

Also, optical storage is inefficient. You can never divide files up exactly into 25GB disks. Back in the old days, we used to divide files into exact 1.44MB floppies using the dd command. Then we would spend 10 minutes walking a box of floppies from Heritage to Crabtree to transfer a sound file. Nowadays, we need to free up 10 hours a week for commuting in a car to pay for an internet connection. Progress.

Optical drives wear out rapidly. Once U commit to optical storage, U forever have to buy new drives. We average 1 drive burnout every year.

What about the perpetual need for optical drives to watch movies? P2P is the most efficient way to watch movies. You can't win against progress, no matter how tough you are, how high you raise taxes, how many people you enslave, or how large your market cap is. P2P is the way it's going to be done.

The only conceivable reason for optical storage is to avoid depreciation. The depreciation on hard drives costs you. You have to throw down $200 to get 2TB, but you won't use the last of it until it's $20. You can buy DVD's in increments. By the time you reach 1TB, you pay the current price for those last bytes instead of what they cost initially.

heroine2200 long version (3 min 31 sec)


Not sure what to do with Heroine 2200. Spent 3 years building DVD robots of one kind or another because a robot that organises disks seemed perpetually valuable & she never forgets. She could be modified to organise any slotted medium. Most likely, 20GB flash drives will become $5 & she'll end up organising hundreds of flash drives.

There is a chance of getting rid of her loading tower & just having 2 storage towers.
Posted by Jack Crossfire | Feb 28, 2009 @ 11:38 PM | 3,247 Views
4 a good time, go to

http://www.wa4dsy.net/robot/six-channel-sonar

Sonar transducers were $1.50 back then.

He could afford dozens of transducers to make it omnidirectional. He didn't have to copy a Maxbotix reference design. He used straight amplifiers & manual gain.

That inspired us & sure enough allelectronics.com has $1 transducers. No more Maxbotix for transducers.

A bit more playing with audible sonar pings & clearly it's a disaster. It's so sensitive to ambient noise, there's no way it would work with noisy fans.

Nothing left but to finish ghetto rotor using GPS.
Posted by Jack Crossfire | Feb 27, 2009 @ 12:25 PM | 3,389 Views
The answer is no. U couldn't survive audible sonar pings 4 more than a few minutes, not even the mighty Ubuubu.

Now what if there was an audible sonar ping you humans could stand. Adding small amounts of noise to the waveform definitely improves it. Receiving musical pings would require huge amounts of electronics.

Noisy 3khz could be close to a jet engine if U concentrate. At 3khz, accuracy drops to 4" but it's a frequency U could filter purely in software, given a 3 channel sound card & perfect realtime capturing which doesn't exist.

U only need 6khz to capture 3khz. 18khz to capture 3 channels of 3khz. 1 output pin to control AGC by PWM. It could probably handle musical pings. If only information traveled slower through air.

There R only 2 speeds information can travel through air:

740mph
300,000,000m/s

That's it. No matter how hard U try, U can't go at any other speed. 100mph would be good for sonar. 1mph would be good for taxes. 600,000,000m/s would be good for paychecks. It's not going to happen. Taxes always go 300,000,000m/s & paychecks always go 740mph.

No matter how much U worship & sacrifice to the god Ububuu, he can never wake up & say, "For renewable sonar, I command the congress to make soundwaves go 100mph. Paid for by just the top 0.00001% of earners! Yay!" even though most of U think he can.
Posted by Jack Crossfire | Feb 26, 2009 @ 01:42 PM | 3,619 Views
Did indeed capture some Maxbotix output using ADC's at 1800Hz & the pings showed up nicely. U could use that for an AGC which defeated reflections, but we're done with sonar. Unfortunately the screenshots R lost, just like the memories of 7.25% sales tax, $1 gas, & $7.50 movies.

Also, before we give up sonar, the optimum frequency for the Maxbotix's was somewhere around 55khz, not the 40khz advertised. The transducers probably need manual tweeking, another reason 3D sonar would have problems.

Finally, tried capturing 10Hz sound with our best condensor microphone. Remember back when U actually bothered with decent microphones & watched home movies on giant screens instead of tiny Goo Tube windows?

Forget about 10Hz sonar. It would take kilowatts of power & ginormous transducers. With a few hundred watts & 30lbs of wood, U can get the condensor to pick up 30Hz.

There are delusions of audible sonar. It would drive people away from the blades. It would be omnidirectional & low powered. The main problem is interference, so what if instead of a sine wave, U spanned several frequencies. The output would be a fixed pink noise pattern U can sense the phase of & a real expensive filter to capture it.
Posted by Jack Crossfire | Feb 25, 2009 @ 01:36 PM | 3,814 Views
Finally got a 1 way sonar test in the air. It was pretty horrible.

Forget about 1 way sonar for large copters, camera stabilization, or any of that other stuff. It's too directional. U would need dozens of the Maxbotix's to cover the full area. It would cost more to make Maxbotix transducers work than to buy an RTK GPS system.

For a large copter, it only works if you're directly over the sensor. No problems with reflections outside. U can go to 15ft before the signal dies. Below 3ft U could fly sideways for some distance. The only explanation is signals bouncing off the ground & off the propellers.

For an indoor micro copter, there's a chance U could fly it in a small box over the transducers.

Your only hope is to find a truly omnidirectional & super powerful transducer other than the Maxbotix. Good luck with that. Don't U know the world is based on mortgages & cars?

Serial port multiplexing was a failure. The XBee packet timing is not predictable enough to stuff data between packets. RTS doesn't work either. It splits packets. Time to go back to 50Hz with dual serial ports.

Anyone serious about commercializing VicaCopter would use bluetooth or a direct USB connection & skip the serial ports.

What about reflected sonar for position sensing? U ask. You'd have to always fly 1 meter away from & perpendicular to 2 walls. It's a $75 tag just for 1 down & 2 sideways sonars. You'd single handedly bail out Minnesota's mortgages.

What about 10Hz sonar? 10Hz would be omnidirectional but requires a very heavy magnet.
Posted by Jack Crossfire | Feb 24, 2009 @ 01:37 PM | 3,846 Views
Another amplifier stage & the dual sonar receivers started working. Anything can be fixed with more op-amps. This circuit is now over 1000000 gain. The receivers worked with all our op-amps, but old problems returned.

12" sensor spacing was pretty good at sensing 2 dimensions in a 4' line 5' above the sensors. Most of the time it got within 1". Distance readings R pretty stable throughout the week, as we increase the sensor count.

Forget about any lower. There's no way a full sized airframe is going to hold its position accurately enough for this to work. We're down to finishing ghetto rotor & flying to higher altitudes with the sonar to get full ranges with engine noise & without reflections.

With all its problems, patents, & high prices, custom sonar is very depressing. Who knows what would happen if the sonar banging was combined with the eternal blizzards of Minnesota.
Posted by Jack Crossfire | Feb 23, 2009 @ 01:26 PM | 3,382 Views
Maxbotix gives no rights for the reference design so you couldn't use it in a product unless you moved to China.

Building your own sonar transmitter, writing your own firmware, & removing all the shrouds produces the best results so far. We have 1/4" precision in the best circumstances & a much wider cone.

The range is still very limited before reflections overwhelm the original signal. Eventually the AGC adapts to the reflections instead of the incident signal.

If the sonar modules point straight at each other, you can get 10ft indoors before they start falling over. Looks like ghetto copter is going to fly in a straight line from the ground station & have a fixed heading.

Being experts in 1 dimensional sonar, you're now ready for 2 dimensional sonar. After fabricating module #2, no op-amp would work besides the 1 we tested all week. Back to the commute.
Posted by Jack Crossfire | Feb 21, 2009 @ 08:58 PM | 4,288 Views
With all the timer issues found, the results are pretty dissapointing. Accuracy is 1", deteriorating as distance increases.

Removing the shroud doesn't make any difference for the receiver but greatly reduces the transmitter power. Suspect it's supposed to amplify the sound by resonating.

The useful range is only in a small cone.

You can improve the range by angling the transmitter & always aiming the aircraft at the receivers but this costs you altitude readings.

Keeping the ground station far away from the amplifier improves results.

The automatic gain control works. It gets as much information out of the transducer as you can get.

The update rate is 15Hz because the Maxbotix firmware can't go any higher.

The Maxbotix firmware is so limited & expensive, probably going to forget about reflected altitude readings & shoot for 3 receivers & 1 transmitter.
Posted by Jack Crossfire | Feb 20, 2009 @ 12:44 PM | 3,423 Views
After another 2 hours in the traffic jams, got all the way to the first unidirectional sonar ranging. Only got it to work by pointing the modules straight at each other. The maximum range was only 5ft. We have broken synchronization, broken XBee multiplexing, broken clock synchronization, broken gain. The number of systems which have to be upgraded for this to work is nihilistic. It definitely has 50 more hours of commuting to go.

XBees are a complete waste of time for an indoor micro copter. Multiplexing XBees with 72Mhz is freakishly wasteful, maybe even more than raising taxes to fund prime Bakersfield mortgages. We only do it to reuse the same equipment with the full sized copters. You'd ideally use bluetooth.
Posted by Jack Crossfire | Feb 19, 2009 @ 02:17 AM | 5,488 Views
There it is. The Jack Crossfire version of the Maxbotix amplifier. No matter how much money your boss makes by copying reference designs, we hate copying reference designs. So after several hours of trying components, made a slightly simpler version of the Maxbotix amplifier. It isn't as stable as the Maxbotix, but it has longer range & you can fix the output in software.

Using Fry's ripoff parts, this circuit + the transducer cost 1/2 as much as buying a full Maxbotix for reception. If you want the full measuring device, you're better off paying full price.

This circuit is extremely powerful. Indoors, it senses the transmitter from 10ft away, mostly omnidirectionally. It can sense the transmitter 20ft away if they're pointed at each other or there is a reflection. The trick with indoor operation is reflections from indoor objects. It won't do as well outdoors. It's sensitive to ambient noise, clapping, & probably aircraft.

Since we caved in & threw in tons of op-amps, we might as well run the transmitter off a 20V op-amp & see how far that reaches. You can also try putting a diffuser under the transmitter. That would require losing altitude sensing by reflection & building 3 of those reference designs, so forget about it until the system actually flies on 5V.
Posted by Jack Crossfire | Feb 18, 2009 @ 12:34 PM | 5,337 Views
So after 7 days, the unidirectional sonar test kit finally made it out of the wasteland. Put a simple 1000:1 high pass amplifier on it. Sadly, it's very directional. The more you amplify it in hardware, the more directional it is. In software, you can do all kinds of things to it, but we don't have the luxury of a 40Mhz sound card.

Running it on 5V definitely improves the range. Unfortunately you're stuck with a very small cone of visibility in front & above the transducer. The range is stuck under 5ft. You'd have to use takeoff tricks again, just like with GPS. Running it over 5V would require a matched impedance power amplifier. You can't just plug it into a BJT.

With the constant rain & all you job seekers pouring in from the wasteland, we're spending hours & hours on the freeway. Only got a couple tests in with the Maxbotix's.

Future options:

Build the reference design.

Grind up the Maxbotix's to try to make them more omnidirectional & forget about using bounce mode for altitude.

You can keep spending money on this until you're up to http://www.evolution.com/products/northstar/works.masn this $1300 positioning system. The web pages have no information & he's got no advertising, but it's machine vision.
Posted by Jack Crossfire | Feb 17, 2009 @ 12:55 PM | 4,591 Views
You can get the worst case drift from the datasheet. They all have a null drift over temperature or zero rate vs temperature parameter. If it's in volts, you divide the volts by the volts per deg/sec parameter. This is the key parameter 4 U.

IDG300: 150 deg/sec
IDG500: 25 deg/sec
ADXRS150: 26 deg/sec
MLX90609 - 150: 7.5 deg/sec
LISY300AL: 5 deg/sec

So we got the 2 worst gyros in the world. 2007 was the dividing line where they got a lot more accurate, except for the Silicon Valley ones. No-one is anxious to spend $100 on LISY300AL prototyping boards, so the idea of accurately predicting the outcome of cheap gyros without buying a PC board is dead.

The days of magnetometers & accelerometers are over. If they're really down to 5 deg/sec, modern IMU's can go for over 20 minutes without any corrections.

FYI, polulu.com has the same breakout boards as $parkfun for slightly less money. The polulu LISY300AL can take 5V & lowpass filters the output. You need a 3.3V reference either way because A/D converters are nonlinear.
Posted by Jack Crossfire | Feb 16, 2009 @ 07:25 PM | 4,037 Views
Still having delusions that 2 years of experience could somehow salvage some use from the IDG300's, put them back in an IMU. Also, if U can get the IDG300's to work, you guarantee any other gyro will work.

They're still pretty awful. The body heat from sitting next to them or the radiated heat of a heatsink throws them off, but they are stable at constant temperature. They would make good thermometers. Can't believe $parkfun still sells them for $75. No Silicon Valley startup is ever going to make good gyros because all the aerospace engineers are in LA.

Thermisters suck. Thermisters require 2 more analog channels. They can't measure temperature inside the gyro package. Without a proven cheap gyro solution, the sonar doesn't have much of a future either.
Posted by Jack Crossfire | Feb 15, 2009 @ 05:12 PM | 4,092 Views
Since the ground station is getting major rework to support sonar, decided to get rid of a serial port.

The answer is yes. You can multiplex a 2.4Ghz & 72Mhz on the same serial port. The trick is to use lots of diodes & carefully time the incomming 72Mhz packets to fall where the incomming 2.4Ghz is normally idle. The outgoing packets are received by everyone. The maximum feedback rate drops to 40Hz & the 2.4Ghz bandwidth drops to 20kbits. The 2.4Ghz has an RTS pin to make it stop sending, but you can't split the 2.4Ghz packets so RTS is useless.

The dual serial port ground station could have been used for anything, but money & complexity is more important. Now it's only for controlling copters, but it's much simpler to set up & cheaper.