marabou depron KFm-2 airplane

Marabou Stork: fixed wing FPV platform

Marabou Stork, my Depron/Carbon/3D Printed FPV airplane is officially done. Although it had first flight a week ago, some technical problems postponed full feature trials until yesterday. I would not call it a "huge success", but it was fine.

Here is a video from some FPV flying:

After around 1 hour in the air, here are some conclusions:

  • Wing is closing to it's limits. Originally it was designed for an airplane that weights around 500g. Marabou Stork weights 900g. Do not get me wrong, it still flies good, I really love KFm-2 profile on it, but you have to start to remember about things like air speed, specially during turns: too much yaw, not enough speed and bam, you have stall. It's easy to recover, no problems there, but last years model (the same wing, less weight) was free of it
  • Neo-6m GPS is, hmm.., crap… I have to update to Ublox Neo-M8 as soon as possible
  • INAV is unable to process GPS altitude and barometer altitude simultaneously: altitude jumps up and down like crazy. For now, the only solution is to disable either baro or GPS altitude component from computations. It's simple and I will try to write few words about it next week
  • Did not tested fixed wing navigation features of INAV yet. Reasons: two points from above
  • Boscam TS-351 200mW 5.8GHz transmitter with crappy clover-leaf antenna behaves much better than expected. I had excellent reception on my Skyzone Sky-01 at 1km and had to return due to RC link RSSI warnings
  • I'm disappointed with FrSky X4R range. Looks like 1km is a safe side limit here. RSSI was dropping to 40 and did not wanted to push it further. Probably it's because crappy antennas. They are equipped with simple whips, not dipoles like X8R for example. Next week I will try connecting 2.4GHz dipole to X4R and will give it another try

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Hand on: DAL (DALprop) TJ5045 propellers

After moving to new, 4S powered, mini-quad based on Reptile X4R 220, EMAX RS2205 2300KV and FVT Littlebee 20A, I’ve discovered that I’m missing some power. DALprop 5040 and DALprop T5040 I’ve been using on 3S did not delivered enough power. So, I’ve gave DALprop TJ5045 a try.

According to specs, they should be most efficient from all DAL 5045 family. Well, efficiency will be determined, one thing is sure: they surely give much more thrust and pitch speed comparing to T5040.

Dalprop TJ5045 top

Dalprop TJ5045

Thrust and speed improved a lot. ATM, hover is at about 32% of throttle and climb rate is impressive. I love it! They also seem to be little quieter that T5040.

Dalprop TJ5045 on Reptile X4R 220

They are also durable. Maybe I’m not crashing as often as before, but when I do, it’s much more spectacular. Today I had two of those spectacular crashes and all propellers survived. Nice.

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Marabou Stork: FPV airplane maiden flight

For the last few week I’ve been little busy building my next fixed wing UAV: “Marabou Stork” Depron/Carbon/3D Printed airplane with pusher prop build for FPV. It’s improved version of “Red Cruiser” model from last year.

marabou stork depron airplane

marabou stork depron airplane 2

It’s equipped with KFm-2 wing, Turnigy D2826-6 2200KV motor, APC-E 7×4″ propeller, 2700mAh Lipo battery, FPV setup with MinimOSD and RunCam PZ0420H camera. And Flip32 running INAV for stabilization and navigation (no GPS yet).

As you can see on a video above, it flies. Even pretty well. It needs some tuning, but have big potential. Unfortunately elevator malfunction grounded it after few minutes in the air.

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How to install and configure Betaflight 3

Latest Betaflight 3.0 is a new quality for flight controller software. It brings many new, cool, features comparing to previous versions. If you fly mini-quad or micro-quad, you have to check what Betaflight 3 has to offer.

This tutorial will show how to install Betaflight 3 and how to configure it so mini-quad can go into the air in under 20 minutes.

To play with Betaflight 3.0 you will need latest Betaflight Configurator! Install or update to latest version.

Flashing

Open Betaflight Configurator

Betaflight Configurator

Continue reading “How to install and configure Betaflight 3” »

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Micro MinimOSD stops overlaying in flight: solution

Both MinimOSD and Micro MinimOSD suffers from irritating technical problem. In some setups, they stops overlaying data during hard maneuvers or even right after arming. Problem is very simple: chip MAX7456 is extremely sensitive in terms of supply voltage quality. Working motors and/or servos, can introduce enough power supply noise to occasionally force MAX7456 to reset.

Luckily, solution is simple: separate LC power filter or big enough capacitor connected in parallel to 5V pads of MinimOSD.

Almost any big enough electrolytic capacitor will do (> 100uF, the bigger the better) but best results can be archived with low ESR > 500uF capacitor.

In my case symptoms were not very strong, usually only very fast flips caused MAX7456 to reset, but I’ve decided to go big: 1000uF low ESR capacitor.

Low ESR 1000uF Capacitor

Micro MinimOSD has 5V pads on a side and they are the best place to attach capacitor.

Micro MinimOSD

As you can see below, capacitor is bigger than MinimOSD itself and I had to think a little how to place it inside my Reptile X4R 220 frame.

Micro MinimOSD with capacitor attached

Results are great: no more MinimOSD problems. OSD stays on all the time, no matter how hard I use the stics.

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Preview: cheap APM Power Module for Cleanflight

Recently I’ve got my hands on a pair of cheap APM Power Modules from eBay with integrated 5V BEC and current meter (90A max). Although they are APM designed and will not work stright away with STM32 flight controllers like Naze/CC3D/SPRacingF3 (or rather would work only once since they are 5V scaled and those flight controllers require max 3.3V input) I have an intention to make them work!

So far, I’ve concluded that:

  • current measurement is done with Texas Instruments INA169 and 0.5Ohm shunt resistor
  • analog current out is 5V scaled, so probably 90A current flow results in 5V on meter output
  • voltage sensor output has 1/2 voltage divider. We can ignore it, most SMT32 flight controllers have voltage dividers (CC3D does not, but 1/2 is not enough in this case)
  • It more less works with a 1/2 voltage divider between current sensor and flight controller. Requires some tweaking, but something is measured. Will require scaling!
  • Integrated BEC works, and this is all I can tell about it I’m affraid

cheap apm power module for cleanflight

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blackbox_header

How to measure gyro noise frequency with Blackbox

Cleanflight / Betaflight / INAV lowpass filter tuning can be a hard thing to do if you have not idea what is noise frequency you want to cancel. Sure, you can blind test or read tutorials. But what if I tell you, you can measure it quite precisely using only Blackbox logs? Or measure rotation speed of motors? That would be nice, isn’t it? The only requirement are few seconds of Blackbox log with visible gyro (it can be also motor output or Pterm or even ACC reading) noise.

blackbox measure frequency 1

Continue reading “How to measure gyro noise frequency with Blackbox” »

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Air Crash Investigation: gone in 6 seconds

“What goes up, must come down”. I had an opportunity to face this old truth 2 weeks ago, when my 600mm quadcopter felt from 30 meters straight into water.

It was supposed to be a simple flight:

  1. take off
  2. fly few hundred meters away with GPS assist
  3. engage Return To Home and land

Dozens of missions like this in last few months, so really, nothing special. Unfortunately, like I mentioned above, not everything went as planned. 2 minutes after take off, UAV lost stability and went down with screaming motors. Continue reading “Air Crash Investigation: gone in 6 seconds” »

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3D Printing: rubber launched glider

3D Printers give almost endless possibilities and 3D printed gliders can be a great weekend project. Last week I’ve printed a small fleet of Monarch XL gliders from Thingieverse. Single glider takes around 45 minutes to print at 50mm/s and few additional minutes to glue all the parts together. Add an hour for a rubber launcher and done. Great fun for a small price. It flies surprisingly well and my daughters loves them.

3d printed glider airplane

3d printed gliders

Flight characteristics improves when dihedral is added. Also elevator can be adjusted, so glider can do loops! Great fun for a very low price!

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PWM, OneShot125, OneShot42 and Multishot comparison

Two years ago it was simple: you wanted to connect ESC to Flight Controller or radio receiver, you were just doing it. There was only one (maybe 2) protocols that allowed to pass information to ESC. It was standard PWM protocol. And it was enough. No, with faster hardware, mini or even micro quads, this one protocol is not enough. So, we also have OneShot125, OneShot42, and Multishot. Should we care? A little.

  • Legacy ‘Analog’ PWM signal – this protocol is not used in multirotor world. It is supported only by extremely limited number of ESCs and radio receivers. 0% PWM duty cycle means ‘Stop’ and 100% PWM duty cycle means ‘Full power’. Modern UAV pilots/builders should not take about it at all. Interesting fact is that BLHeli supports it as PWM Input option that is disabled by default.
  • ‘Standard’ PWM signal – I’ve previously described this protocol here. To recall: protocol encodes requested output as a length of a pulse. Pulse length of 1ms means ‘Stop’ and pulse length of 2ms means ‘Full power’. Because of this, maximal theoretical update frequency is 500Hz (490Hz in practical applications). Signal delay in case of PWM protocol is 2ms. It means, that ESC can start to update output 2ms after flight controller started to send this information. All of that makes PWM rater slow, and using looptimes below 2000us (refresh rate 500Hz) makes no sense.
  • ‘OneShot125’ protocol – this protocol uses 8 times shorter pulses than standard PWM protocol: from 125us (stop) to 250us (full power). That means 2 things: it allows for 8 times faster PID control loop update rate (looptime 250us / 4kHz update rate). It also has 8 times shorter signal delay: only 250us instead of 2000us. Currently, OneShot125 is the minimum for mini quads. Even bigger machines will appreciate smaller delay. Supported by most flight controllers and ESC (SimonK, BLHeli, KISS, other). If both Flight Controller firmware and ESC supports OneShot125, it should be used.
  • OneShot42 is 3 times faster version of OneShot125. Max 12kHz update rate and 42us signal delay. It was developed by Flyduino as part of KISS FC and ESC ‘program’. Not widely supported yet.
  • Multishot – the fastest ESC protocol in this comparison, developed by RaceFlight, allows for 32kHz update rate. It is almost 10 times faster than OneShot125 (80 times faster than PWM). Requires both fast FC (preferably STM32F4) and fast ESC (Silabls F390 preferably). Not widely supported mainly because of limited number of ‘Multishot ready’ ESCs. And it has fancy startup melody too… man….

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