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Archive for July, 2012
Posted by Jack Crossfire | Jul 31, 2012 @ 09:48 PM | 3,718 Views
Years ago, 10V seemed to improve the range of single direction sonar. In reflected mode now, it completely destroyed it. At 10V, the range started to decrease. By 20V, there's no detected reflection at all.

At 20V or 40V peak to peak, the sensor actually seemed to stop receiving. Maybe the diodes broke down. Maybe the sensor heated to a point where it can't receive. The ordinary Radio Shack diode breaks down at 25V. Maybe the diode magic degraded it.

Nothing has worked over carpet. It's hard to believe anyone is using reflected sonar over carpet, unless it's a ridiculously low altitude.

Reflected mode goes at 20Hz, by shortening the pings to the absolute least amount of time. The sensor rings for a fixed amount of time after the voltage is cut off, so the idea of driving it is just to get it started, like a hammer hitting a string. It may work with only a single pulse.

The Maxbotics probably gets shorter ranges by measuring how long the sensor rings, then for distances below 14", it measures the end of the ringing.

There's also the chance reflected & single direction can be combined to produce a more accurate distance. Lots of things to try, with the winner whoever picks the right things 1st.


In other news, the next laptop arrived ahead of schedule, a 2.3Ghz Intel I3 with 4 hyperthreaded & 2 physical cores. When it dies, the super slow EMachines with 1Ghz AMD dual core will finish the rest of its life. Having this upgrade definitely makes the last year with the EMachines look like a simpler, impoverished time.

As with the Intel I2 from 2008, it's much faster & smoother than the AMD at the same clockspeeds, but has only 1/4 the battery life of the AMD. It's much faster than the 1st 2.4Ghz laptop, a super expensive 2.4Ghz AMD single core from 2005.

Hyperthreading has improved drastically, over the years. In 2010, hyperthreading slowed down compilation. Now look at the difference:

4 cores: 48s
2 cores: 1m29s

The Intel requires a 4S battery where the AMD used a 3S battery.
Posted by Jack Crossfire | Jul 29, 2012 @ 10:29 PM | 3,885 Views
Reflected sonar data is required for any 3D sonar system, so it's time to design 1 sensor to transmit & receive. The Maxbotixes are too directional. The Parralaxes are too heavy.

The mane problem with using 1 sensor & probably a mane reason why Parralax uses 2 sensors is 1 of the transducer leads has to be switched to an input to receive, limiting the drive voltage to the microcontroller voltage.

Your best bet is a motor controller which directly passes the input to the H-bridge, so you can generate rapid toggling & high impedance mode on 1 pin while grounding the other pin. None of the existing motor controllers seem to do that.

Another idea is driving it with its full peak-peak voltage in 1 direction only. A boost converter is required either way & it's cheaper. Mechanically, the transducer probably can't produce as much SPL with a half wave.

There is some diode magic which can be applied to op-amps to make them tri-state.

Finally, there is the Leap Motion solution. That seems to use 2 IR cameras to detect distance & oscillating IR leds to separate an object near the sensor from the background. It would have a lot of restrictions on its use in a space larger than immediately above the sensor. The larger the space, the more likely the LEDs can't separate the foreground from the background.

Dual cameras are still an intriguing option for vision. It would still require an expensive gimbal.
Posted by Jack Crossfire | Jul 29, 2012 @ 04:45 AM | 4,030 Views
Because of the lack of jobs, the Marcy class aircraft have tended to shift more towards a product than an open source hobby.

15 years of doing 1 open source project or another have never yielded any career benefits from the open source aspect of it. They might care about the final product or the experience from developing it, but no-one ever offered a job because the source code was free & no-one who copied my source code to advance their job ever offered a pat on the back.

Part of the problem is it takes a lot more support than development for the open source aspect to gain enough popularity that it enhances your career. You have to be more of an organizer & the development has to be more in line with what the masses look for in other products right now, not a science project. Compromises like a 4Hz update when you'd like 30Hz or a clunky touch screen interface when you'd like a bulletproof tactile interface have to be accepted, because the platform has to be what the masses want right now.

In open source RC projects more than web servers, the developers tend to have jobs other than programming. They're competent enough at programming to make a career out of it, yet they're not offered jobs & they don't seem to seek any.

What seems to be happening is people who work on web servers are interested in software for its own sake. People who work on RC projects are using software as a tool to solve another problem that they're more interested in....Continue Reading
Posted by Jack Crossfire | Jul 28, 2012 @ 09:20 PM | 3,944 Views
A lot besides sonar was done in the last 3 years, but the matter of making something bulletproof for an ordinary consumer requires revisiting it. The PCB fabrication has improved, since those days.

Jumper resisters of varying sizes have replaced most vias. Where vias are unavoidable, magnet wire has replaced wrapping wire. Chip capacitors have replaced through hole capacitors. ARM has replaced PIC. Single layer boards have replaced dual layer boards. They're lighter & cheaper when home made. Upside down etching has replaced manually shaking the acid. Leaving bare board has replaced flood filling, to reduce weight. Isolating solder points with small traces has given better solder balls. Having all connection points on the edge of the board has replaced scattering them throughout the board. Soldering molex connectors directly to the board has replaced umbilical wires. 1200dpi has replaced 600dpi. Landscape mode has replaced portrait mode, because the printer warps the long direction.

3D sonar using all 4 transducers for reception is the latest experiment. Surely, all these experiments have been done & given up on, before.
Posted by Jack Crossfire | Jul 27, 2012 @ 03:00 AM | 4,672 Views
Manually flying Marcy 1 in a large room (5 min 18 sec)


Had a rare opportunity to fly her in a large room, at a cost of $100/hour. For the 1st time, could see how stable she really is. She's so stable, manual flight with a keyboard is possible. The hardest part was controlling altitude. The autopilot still does a better job, even compared to a human with proportional sticks. It's a wonder humans still fly airlines.

...Continue Reading
Posted by Jack Crossfire | Jul 26, 2012 @ 01:47 AM | 4,241 Views
Had a rare opportunity to fly Marcy 1 in a large room, at a cost of over $100/hour, revealing for the 1st time that she was extremely stable in every direction except altitude. Horizontal position holds really solid. Vertical position needs constant tweeking. Using a keyboard instead of a proportional stick made it very challenging to control altitude.

Also revealed was that the cyclic phase seemed to be different in the air than on the ground. It may have always been offset, but unnoticeable on the ground.

Horizontal position was super stable, yet translation was very effective. Pull the cyclic & she moved pretty fast. Center the cyclic & she stopped immediately, all without any electronic stabilization. The aerodynamics of Marcy class vehicles have certainly been hashed out.

Where the Picco Z rotor was the breakthrough in cheap cyclic damping which made toy copters popular, the next wave will be cheap altitude stabilization.

Sadly, autopilot in this room was a complete failure. It was certainly no fault of the aerodynamics. Something has gone wrong with the autopilot in the last 6 months.

The memory of being able to guarantee a stable takeoff, hover, & landing with every single autopilot run is still fresh. It was so reliable, I would walk around with a camera while the autopilot took off & hovered, unattended. It would be nice to work on getting back to that state, with the proven machine vision system, but financial reality dictates focusing on a better position sensing system.
Posted by Jack Crossfire | Jul 25, 2012 @ 03:15 AM | 4,437 Views


Without Marcy 1, there would be starvation. The Marcy Mogul is insane, but when you need to pay the rent & she's the only way, there's no more budget for argument.

With rare access to a larger room, these aircraft have done some pretty impressive flying with preprogrammed horizontal translation & ground based vision. There are lots of problems with ground based vision & control, but when it works, it works.

The control problems definitely put you off of ever selling it as a product, but there is hope that the problems are manely with position sensing rather than the airframe design.
Posted by Jack Crossfire | Jul 20, 2012 @ 03:45 AM | 4,313 Views
Quickly bringing the sonar airframe up to a minimal flying condition showed all those extra clockcycles & radios still didn't get sonar over the hill. It may have been marginally better, but already getting a Marcy aircraft to fly indoors showed it took absolutely glitch free, razor accurate altitude data. The problem with ground based sonar is not the range or the directionality, but it glitches.

Horizontal data seems good enough. There's definitely a future for it if it's combined with a straight down sonar for altitude. Straight down sonar would work, if an amplifier was put on the flight board. The processing would have to be done in software, since hardware to detect reflected sonar on 1 sensor has been patented out of existence. It may be patented in software, too.
Posted by Jack Crossfire | Jul 17, 2012 @ 11:42 PM | 4,543 Views
Now there's some hasty soldering. Only now do you remember you don't know the true camera dimensions. Took 8 hours for the fabrication up to this point. It was harder from using the wrong size components. Hand soldering is no way to mass produce it, but if the demand is under 20, hand soldering may be good enough. Having only a single layer makes it big.

Can't remember a board revision this easy to bring up. Having all those luxurious ARM features is a lot easier.
Posted by Jack Crossfire | Jul 17, 2012 @ 04:50 AM | 4,427 Views
So laser printed boards require 2 transparencies to get enough darkness. After having many fine pitch boards come out bridged because the laser printouts on 2 transparencies never lined up, it became clear that the printer couldn't replicate the exact same size on 2 printouts.

After printing out a very long & narrow board, it became clear that the spacing was warped in the vertical direction, because the roller speed wasn't stable. Long & narrow boards have to be printed out with the long side facing sideways. The horizontal dimension was stable.

The next Marcy 2 prototype was a very long & narrow board.



It also became clear, after spending another full day laying out yet another prototype which has no application to a final product, it's going to cost $25,000 to bring this gadget to a final product & it's only expected to generate $2000 in revenue.

There's no way it's going to replace day jobs, which are damn rare. The cost of living needs to decrease or an investment bigger than $25,000 needs to be found, or a way to get blessed during soulmate hell needs to be found.