HC-12 433MHz RF serial module range test

As I mentioned in my first post about HC-12 433MHz radio modules, I’ve put my interest in them for telemetry purposes. While S.Port telemetry I’m using in FrSky Taranis radio might have higher range than HC-12, it is closed environment. Since $10 for a pair of HC-12 is not much, I’ve decided for more open DIY solution.

Setup on a quadcopter consist of one HC-12 configured for FU3 mode and baud rate 9600bps connected to SPRacingF3 UART3 port and “air cooled” (shortened with a coil) 433MHz whip antenna. Well, to be precise, it’s 450MHz since I changed working frequency. Antenna is not tuned or scientifically computed. Just 433MHz version shortened a little using proportions. Antenna is mounted on GPS mast. In next version I will probably replace whip antenna with Vee antenna.

HC-12 Rf 433MHz module in quadcopter

"Air cooled" antenna on quadcopter

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The best way to mount LiPo on a drone: 3M Dual Lock

LiPo battery, as the heaviest single element of any racer quadcopter, is mostly the first one to fell off during crash. Or displace in high-g maneuvers. Or simple fell off in flight. Like on this picture below I’ve found on Reddit. Grrrr… for sure this is something I would like not to see personally again. And I’ve seen it on my first build based on X525 frame.

battery fell off

So, solid and strong battery mount is a must. Battery strap for sure. Even few in case of heavier ones. But battery strap is not enough. LiPo can always slip out. To prohibit that, I’ve been using velcro strips and it worked fine. But velcro has a few drawbacks: it is not very strong connection, allows some movement, and looses strength after some time. Few weeks ago I’ve discovered something that is way way better than regular velcro: 3M SJ3550 Dual Lock Reclosable Fastener. Read More

Drone vs. passenger airplane

Let’s be honest here: some drone pilots are stupid and fly very close to airfields. Big commercial airfields with tons of passenger traffic. Why? Ignorance, lack of knowledge, craziness, lack of imagination or just plain stupidity. On the other hand, commercial airplane pilots see drones everywhere. Few weeks ago grand hysteria: drone hit a plane at Heathrow. Who did it? Why? Laws should be more restrictive! Two days later: do, drone did not hit anything. So, what pilot reported? Probably it was white plastic bag. Eh…

The main problem with drones and commercial air traffic is that nobody know what would happen if for example DJI Phantom would hit Boeing 747. We more less know what happens when a goose hits one. It happens quite often. We also know when happens when a turtle hit and airplane on runway. Yes, it happens too. Hey, we even knows what happens when frozen chicken hits windshield. But drone? “Keine Ahnung” like Germans would say.

Now there is chance our knowledge on that topic would improve. EASA, European Aviation Safety Agency, decided to create a task force that will investigate potential results of drone-airplane collision. It will:

  • investigate incidents
  • analyze existing research
  • investigate weak points of airplanes: windshields, wings, engines in context of UAV collision
  • consider the possibility to do further research and perform actual tests

First results should be available at the end of July.

Make your drone stands out with insulating tape

Everybody knows that red is the fastest color. Ferrari has proven that years ago. With red Turnigy Graphene LiPos I’ve bought recently, I’ve decided to make my ZMR250 quadcopter stands out a little. In a cheap and dirty way: if I have red battery on top of ZMR250 and I can buy a propellers in almost any basic color, why not to go one step further?

Idea of making the whole drone red was in my head for a second, but it died a sudden death. Paint would not do. Too fragile and too effortful. Instead I’ve visited a hardware store and purchased color insulating tape. They come in different prices, sizes, qualities and of course colors. Classical black, green, blue, yellow, red, etc.

At home I’ve applied red tape around arms and ESCs. That also allowed to get rid of zip ties that I used to hold ESCs in place before. They were not good. Insulating tape is not only stronger by also protects ESCs better from dirt and water.

Red is the fastest color on 250 quad

Effect? Quite nice, I like it very much. Red props (DAL T5040 that I will review soon), red arms, black carbon and Turnigy Graphene are looking nice together. And this ZMR250 for sure no longer looks like regular ZMR250. All for just a few cents worth of insulating tape!

HC-12 433MHz wireless serial communication module configuration


HC-12 are cheap 433MHz wireless serial port communication modules with a range up to 1800m in open space. They are SI4463 based. Each costs about $5 when bought from China, and 2 of them can create wireless UART link that can be used, for example, to transfer telemetry data from UAV. Or drive IoT device. Or connect sensors. Or whatever else one can think of.

HC-12 433MHz wireless serial communication module

It is based on SI4463 RF chip, has built in microcontroller, can be configured using AT commands and allows to use an external antenna. Working frequency is divided into 100 channels starting from 433,4MHz up to 473,0MHz with 400kHz channel separation. Maximum output power is 100mW (20dBm) and receiver sensitivity differs from -117dBm to -100dBm, depending on transmission speed. It accepts 3,2V-5,5V power supply and can be used with 3.3V and 5V UART voltage devices (5V safe). Read More

Setting up iNav on 250 class racer

Although iNav (iNavFlight) with advanced GPS and navigation support is best suited for larger, GPS equipped drones, there is absolutely no reason not to use it on something smaller like 250 racer. Why? Well, why not? Basic flight mechanics is the same like in Cleanflight or Betaflight. FP-PID is brand new PID controller, not very popular and not very well documented, but in many ways superior to LuxFloat. The way it handles D term is just outstanding. It can be pushed very, very high without introducing noise.

OK, it has a drawback. High computational requirements and floating point logic causes users of STM32F1 based flight controllers like Naze32 or CC3D can forget about looptime 1000us. 1400us is all those boards can do. On the other hand, looptime 1000us (or even 500) is quite new thing introduced and made popular only about half year ago. And people were racing before that somehow… So, 2000 is not that bad after all. Good thing SMT32F3 board are strong enough not to have to worry about this issue. So, let’s go! Read More

Three flying weekends with Turnigy Graphene batteries

It is still too early to decide if new Turnigy Graphene are worth the money, but after 3 flying weekends with them I do have some thoughts about them already.

Turnigy Graphene LiPo Battery

  1. They discharge differently than Turnigy Nano-Tech I’m using in parallel. Discharge curve seems to be flatter
  2. Voltage drop on high load is much smaller comparing to Nano-Tech. Also, they do not regain voltage when disconnected. I usually try to fly until voltage goes below 3.5V per cell. More less 4:30 up to 5 minutes of flight with my regular style. Before charge Nano-tech’s voltage usually goes up to 3.7V. With Graphene, it’s different story. Before charge voltage per cell is around 3.65V. Maybe it’s only half volt, but does tell something about discharge curve and general battery performance
  3. Althought they behave different than Nano-techs, they both accept more less the same charge during load
  4. My Graphenes are new, while Nano-techs not, but Graphenes seems to balance faster. Looks like cells are a better match. I still would have to confirm this
  5. They are indeed quite heavy, but I did not noticed lower flight times or worse performance

Requested: iNav CLI dump

Because I’ve received few requests to share iNav configuration that allowed performance like showed here and here, below you can find most important parts of my configuration. I’ve removed some parts like AUX, serial configuration, MAG and ACC calibration. They are mostly iNav defaults, no special tweaking was made. I hope this will help.

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iNav: Waypoint Mission

This video was taken few weeks ago during my tests of Waypoint Mission implemented in iNav.

Hardware setup:

  • Transporter Q7.6 600mm quadcopter frame
  • SPRacingF3 Acro with BMP085 external barometer
  • Beitian BN-880 (ublox Neo-M8M)
  • 10×4.5″ APC props
  • EMAX GT2218/08 1100KV motors
  • 5000mAh 3S battery

Software setup:

  • iNav pre 1.1
  • Default navigation PIDs
  • Slightly tuned FP-PID, quite close to default values
  • GPS nav model: HIGH_G set gps_nav_model=HIGH_G
  • Velocity calculation done by GPS module set inav_use_gps_velned=ON

Mission plan:

  1. Take off in Angle model
  2. Follow 3 waypoints on total distance of about 300m, constant altitude of 10m
  3. At last waypoint goto Position Hold mode
  4. Manually engage Return To Home mode
  5. Automatic RTH and land