Chasing airplanes is cool

Chasing airplanes with drones is cool. Do not try to argue 🙂 But airplanes are cool too. So here is a short video my friend shoot some time ago:

Drone pilot: Krystian

Flying wing pilot: me (I had no idea I was chased)

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If not HC-SR04 then what? US-100 maybe….

A week ago I wrote that HC-SR04 ultrasonic rangefinder is crap and it is still true. Only around 1m useful range and very jumpy behavior above are at least problematic…

There is a better solution. US-100 ultrasonic rangefinder. Comparing to HC-SR04, it has at least twice the useful range. My preliminary tests gave solid readout over concrete up to 2 meters and something. Let's call it 2 meters. But what more important, US-100 was reporting out-of-range state instead of some random values when being out of range! Huge step forward comparing to HC-SR04.

us-100 is much better than HC-sr04

Unfortunately, better does not mean good. US-100 also has some problems.

us-100 is much better than HC-sr04  ut still not good

Readouts becomes "jumpy" at the edge of useful range and they are far far away from declared. But OK, declared always means "perfect conditions". Still, trust me on this, comparing to this, HC-SR04 is crap…

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Marabou Stork decommissioned

Depron airplanes are easy to build, but also do not last long. Few weeks ago I decommissioned by Marabou Stork. It did not crashed, it was flying almost fine, but it had at least a few problems:

  1. Motor was overheating. Just like that
  2. Wing that I originally designed for something weighting around 450g, now had to work with twice that much weight. Take offs were, at least, problematic
  3. It was big and slow and was not giving enough fun

Marabou Stork Depron FPV airplane

So, to paraphrase Monty Python:

This is a late marabou stork

It's not a complete end of this design. Wing is still in pretty good condition and I have a plan to reuse it in experimental twin-motor design. But that later this year… In a mean time, last video footage.

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DemonRC NOX5 racing quadcopter is done

It took my time with this build, that is sure… Somehow there were always more important things to build. Anyhow, DemonRC NOX5 FPV racing quadcopter is finally up and running. DemonRC NOX5 quadcopter

What is inside? Nothing special:

  • Frame: DemonRC NOX5
  • Flight controller: Airbot Omnibus F4 v4 running Betaflight 3.1.7
  • ESC: DYS XSD30A BLHeli_S
  • Motors: EMAX RS2205S 2300KV
  • Camera: RunCam Swift2 2.1mm lens
  • Video transmitter: TBS Unify Pro v2
  • RX: FrSky X4R-SB
  • Propellers: DAL T5045C Cyclone

DemonRC NOX5 quadcopter

DemonRC NOX5 quadcopter

As a bonus, 3D printed TPU GoPro Session mount. But the bottom line is, it flies!

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INAV 1.7.2 has been released

“Let’s do the news….” and INAV 1.7.2 has been released yesterday. Besides new targets (MATEKF405, Alienflight F7, SP Racing F3 NEO) there are few quite important changes:

  • ADC channel to function mapping is now configurable. Any ADC using function (battery voltage, current, RSSI) can be assigned to any ADC pin. You smoked Current pin? No problem, now you can use RSSI for that. It can be done using vbat_adc_channel, rssi_adc_channel, current_adc_channel, airspeed_adc_channel CLI commands
  • Support for analog pitot tubes, based on MPXV7002DP, known as APM Airspeed Sensor. It requires some hacking, but is pretty simple. I will publish detailed instructions in a next few days
  • Servo handling improvements:
    • servo min and max now do what they are supposed to be doing: output is scaled to reach them on max/min input, not just clip. And that means, that aileron differential is not super simple to archive
    • servo rule speed is now defined as 1 speed = 10 us/s. So, speed 100 means that full servo sweep will be done in 1 second. speed 50 means full servo sweep in 2 seconds and so on
    • smix min and max parameters were removed
  • Support for eLeReS receivers built into KFC flight controllers
  • Total flight statistics via stats, stats_total_time and stats_total_dist CLI commands
  • AnyFC F7 improvements:
    • buzzer on output #9
    • SD card detection is now configurable via sdcard_detect_inverted
    • support for external barometers using ANYFCF7_EXTERNAL_BARO target
  • Fixed wing landing after RTH that I already described here

Full list of changes is available here.

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HC-SR04 is crap and there is nothing you can do about it…

Only few days ago I mentioned that I started to reintroduce sonar support to INAV. When DigitalEntity told me that popular HC-SR04 is crap I did not belived him. I expected that “official” 4m range on a noise-machine aka quadcopter is unrealistic, but data I recorded today clearly shows: HC-SR04 is crap and is absolutely not suited for quadcopters and probably other UAVs. Why? Because it goes nuts and starts to pick background noise instead of surface.

Let’s take a look here:

Bottom trace shows pseudo Signal-to-Noise-Ratio (SNR) while top one shows raw HC-SR04 altitude and INAV position estimator altitude (GPS, barometer and accelerometer combined). As you can see, it’s not that bad. There is a correlation between both of altitudes and SNR is pretty low.

Same thing is happening here. Quadcopter descended to land, both altitudes went down to finally meet at zero. SNR is low too. Nice.

But, very bad things starts to happen as soon as altitude crosses 1.5m. Not only SNR goes up, but HC-SR04 starts to report completely unreliable data! If it was reporting out-of-range state, it would be fine. But no, it keeps reporting something between 1 and 2 meters while real altitude is much higher. Total crap.

Conclusion is simple: HC-SR04 can be used on multirotors but only on very low altitudes. Something like 0.75m over concrete. Or 0.5m above short grass. Or even less over long grass. Definitely not good enough for terrain following flight mode.

Next week I will test US-100 ultrasonic rangefinder. It is supposed to give much better results. I hope so…

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Flight Controller Soft Mount – is it worth it?

Is it worth to soft mount flight controller? Are gyro pads I recommended here better than rubber stand offs? I feel that they are better, but I do not have any solid data to prove it. So I can only tell, that I find them better and that is all. But, I can answer the question is it worth to soft mount flight controller at all. The answer is YES and here is a proof…

The problem of twitching motors

After I updated my 5″ racer to stronger motors (EMAX RS2205S 2300KV over RS2205 2300KV) I noticed something very very irritating: twitching motors. When throttle was in more less middle position or after rapid throttle change, twitching from motors was very audible. Quad was flyable, but performance was very low. I had to reduce yaw P gain by more than 50% not to see those twitches in FPV footage!

Blackbox log revealed the truth: from time to time, strong vibration was getting into yaw gyro traces. I also localized the source of those twitches: stronger motors with more torque and higher radial acceleration were able to shake whole machine when frequency was close to the resonance frequency of the frame.

hard mount twitch example

Continue reading “Flight Controller Soft Mount – is it worth it?” »

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And the most popular flight controller for INAV is…

Did you ever wondered what is the most popular flight controller? Hardware I mean. I can tell you 🙂 OK, maybe it will not be a full truth, since I have data only from INAV, but assuming that distribution for Betaflight and Cleanflight is similar, we might know what is happening…

Important, this is not the number of boards flashed with INAV, but rather number of times a board was connected to Configurator!

This counts TARGET software name, not retail name. For example, all clones of Naze32 will be counted as Naze32

Data was taken in June 2017, multiple connections during single user session are stored as single entry. Continue reading “And the most popular flight controller for INAV is…” »

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GPS Racer: worklog #8 – sonar test platform

I honestly admit, that my 6″ quad (codename GPS Racer) was never very pretty. It was just ugly with that GPS tower on the front. Today it got even uglier: I’ve equipped it with HC-SR04 sonar connected via I2C bus (ATtiny85 to the rescue).

Why, you might ask, have I done something so useless? Answer is simple: to make it less useless. There are at least few problems with sonar and modern flight controllers. First of all, most new boards does not have connections for it. Second of all, it does not work reliably.

HC-SR04 test platform for INAV

It just don’t. It was no unreliable that INAV, for example, disabled it for some time completely. Right now it is back, but used only during landing on multirotors. No terrain following or anything like that. Continue reading “GPS Racer: worklog #8 – sonar test platform” »

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