GPS Racer: worklog #2

I’m once again realizing, that doing multiple things at once is not a way to work. Something like that happened to my GPS Racer project. According do original plans, week ago I was only supposed to wait for FPV camera.

Instead of that, only yesterday I finished ESC and motor assembly. But OK, it was a little trickier than I expected originally:

  1. Since I wanted to reuse onboard current meter of Airbot Omnibus F4 (v2) Pro and use Matek XT60 PDB at the same time, I had to do some creative wiring between XT60 plug and PDB. Instead of directly connecting XT60 plug to PDB, + first goes to current meter on Omnibus F4 Pro and then goes back to PDB. Not pretty, but works. I still have to design some kind for power plug holder, but this topic can wait. I still have no FPV camera
  2. I had some problems with ESCs. Not only I’ve destroyed Motor1 soldering pad, but failed to flash FVT Littlebee 30A with latest BLHelli. Bootloader survived, but BLHeli was gone. I have to connect ESC to other FC and then reflash. I wonder if it was hardware or software issue…
    Right now, apart from FPV gear, FrSky receiver, GPS mount, SmartPort inverter and final assembly GPS Racer is few steps closer to being finished. With upcoming Easter, it should be functional in April. Can’t wait…

Mini Flying Wing: MiniWing v2

Miniquads are fun, right? After all, there is a reasons most uf us flies 210-250 quadcopters. If so, small flying wings should be fun too! I tried that already in late 2015 and failed miserably! My design did not survived maiden flight. Well, things like that happens from time to time, so few months ago, after learning few new things, I’ve made a second attempt. And this time I’ve succeeded.

Continue reading “Mini Flying Wing: MiniWing v2” »

Project “GPS Racer” – worklog #1

I know that I should not start new project when old one are still in progress. I really, really know that. But since I’ve somehow lost my interest in Project Dualcopter and I have a real need for a new quadcopter, Project “GPS Racer” has finally started.

What is GPS Racer? During my work as INAV developer, I’ve realized that I do not have a good platform for it. The only GPS enabled multirotor I own is Sparrow Hawk. And it has a gimbal, weight 2kg and is hard to transport. When Sparrow Hawk crashes, there is always something broken.

So, to be able to test navigation related features of INAV, and not have to rebuild every single crash, I’ve decided to build dedicated UAV. For most elements I will be using parts that I already have. I only had to order frame, propellers and GPS module. Continue reading “Project “GPS Racer” – worklog #1” »

Project Dualcopter – worklog #2

3 weeks after my first post on Project Dualcopter, it's time for small update. The plan was to install servos and control surfaces. Instead, I've done:

  • Basic electrical wiring for motors and ESCs. They have power now and are ready to be connected to flight controller
  • To level shelf (above propellers) designed to hold flight controller and radio receiver
  • Think for a moment about landing gear. Yeap, there will be some sort of shock absorbers
  • Think for a moment where battery will be placed: as low as possible to keep center of gravity below center of thrust
  • Decide which propeller should run clockwise and which should run counterclockwise: top should go clockwise, bottom should go counterclockwise

dualcopter esc soldering

dualcopter esc

ATtiny85 Light Sensor – I2C slave device

I love AVR ATtinyx5 series microcontrollers. They are cheap, easy to use, they can be programmed just like Arduinos and comparing to their size they offer great features. For example, they can be used as a remote analog to digital converters connected to a master device using an I2C bus.

Background: A few years ago I've built a weather station based on Raspberry Pi. It collects various data and displays them on a dedicated web page and Android app. Every few months I try to add a new sensor to it. Last time it was a daylight sensor. Raspberry Pi does not offer ADC inputs and I had a few ATtiny85 on hand tat hand. One to another, a few hours later: a photoresistor based daylight meter sensor connected via the I2C bus.

ATtiny85 as light sensor with I2C bus

Electric assembly is pretty simple: ATtiny85 directly connected to Raspberry Pi via I2C, photoresistor with 10kOhm pull down connected to ATtiny85 and signal LED.

attiny85 i2c slave light sensor with photoresistor

Code driving this rig is also pretty simple: watchdog timer wakes up ATtiny85 every few minutes, measures voltage, filters it and stores in memory. Every time read operation is requested, last filtered ADC value (10 bits as 2 bytes).

I2C support is provided by TinyWireS library that configures USI as an I2C slave.

/**
 * This function is executed when there is a request to read sensor
 * To get data, 2 reads of 8 bits are required
 * First requests send 8 older bits of 16bit unsigned int
 * The second request sends 8 lower bytes
 * Measurement is executed when a request for the first batch of data is requested
 */
void requestEvent()
{  
  TinyWireS.send(i2c_regs[reg_position]);

  reg_position++;
  if (reg_position >= reg_size)
  {
      reg_position = 0;
  }
}

/*
 * Setup I2C
 */
TinyWireS.begin(I2C_SLAVE_ADDRESS);
TinyWireS.onRequest(requestEvent); //Set I2C read event handler
`</pre>

Example code to read from device might look like this:

<pre>`Wire.requestFrom(0x13, 2);    // request 2 bytes from slave device #0x13

int i =0;
unsigned int readout = 0;

while (Wire.available()) { // slave may send less than requested
byte c = Wire.read(); // receive a byte as character

if (i == 0) {
    readout = c;
} else {
    readout = readout &lt;&lt; 8;
    readout = readout + c;
}

i++;
}

Serial.print(readout);

Full source code is available on GitHub and my Weather Station with almost a year of light level history is available here.

Project Dualcopter – worklog #1

Flying season 2016 is slowly coming to an end on northern hemisphere. That means less time spent on an airfield and more time spent behind a desk. For this autumn I've found a very interesting, small project: Dualcopter.

Dualcopter is an UAV with two coaxial contra-rotating propellers and 2 control surfaces driven by servos. Lift and yaw are controlled by propellers, while pitch and roll by ailerons placed below motors. This video illustrates how it looks like:

My Dualcopter will be slightly different. Instead of foam and wood I will use 3D printed parts connected together CA glue and zip ties. Maybe it will not be super strong and probably will not survive any crash, but should be enough to make it fly for a minute or so. Almost all parts would be either 3D printed or taken from spare box. I'm not planning any new purchases.

Planned specs:

  • Motors: Turnigy MT2213 935KV
  • Props: APC 1045 MR
  • ESC: Afro 20A
  • FC: Flip32 probably with INAV inside
  • Battery: 1300mAh 3S
  • Weight: around 800g with battery

dualcopter 1

So far, after 2 evenings I have this:

dualcopter 2

Two motors mounted on a frame.

Next step would be to build bottom section with ailerons and battery compartment.

RedCruiser – DIY Depron airplane for FPV

Few months ago I’ve wrote about my first handmade Depron airplane. It was cool design. Super simple, with KFm-2 airfoil, durable and easy to fly. But it had few serious flaws:

  • motor mounted in front of fuselage is great for flight characteristics, but propellers breaks all the time. Even with prop savers,
  • big fuselage is not the same as fuselage with a lot of space inside.

Depron KFm-2 airplane with pusher propeller

That’s why, I have build a second Depron airplane. This time with pusher propeller mounted on a tower behind wing. Wing is almost the same design as in my first airplane. It is still an KFm-2 (Kline-Folgeman, modified) airfoil, 150mm chord, 12mm thick. But is a little shorter: 1200mm instead of 1250mm. The main difference is inside wing. Instead of carbon fiber spars I’ve used two carbon fiber 6mm pipes. That gives plenty of stiffness. Wing almost does not bend in flight, even during hard maneuvers. And generates more than enough lift to give nice, slow flying experience without danger of heavy stall. You really have to want to stall it. And event when it stalls, it recovers nicely: drops a nose, dives for a second or two, and you have lift again. No need to work with rudder, just let it dive and gain speed and then level.  Continue reading “RedCruiser – DIY Depron airplane for FPV” »

Dead Rat, wooden quadcopter, maiden flight

Last week I was, finally, able to perform a maiden flight of my DIY wooden quadcopter (here and here). I will not say it was huge success, but it was a success alright. What went like expected? Well, quite alot. First of all, it flies and has enough thrust to weight ratio to do flips and rolls. And is pretty stable in hover. What went not like expected? It is highly unstable on yaw. Really, really unstable. Probably rear propellers are too close to each other and I have to work on PID settings. As soon as I will have enough spare time…

In a mean time, here is a short video from DeadRat’s maiden flight:

Final configuration goes as follows:

  • Motor to motor diagonal: 500mm,
  • Motor to motor front arms: 370mm,
  • Motor to motor rear arms: 300mm,
  • Materials: 3mm plywood and 15mm wood spars
  • Motors: Suppo A2212/13 1000KV
  • ESC: XT-Xinte 30A
  • Flight Controller: OpenPilot CC3D (clone)
  • Battery: Turnigy 5000mAh 3S 25C
  • Propellers: Gemfan 1045
  • Start weight: 1212g
  • Hover time: 21 minutes

Next steps: tune it up and move battery to top. Somehow I do not want to construct a landing gear for it…

Wooden quadcopter, work continues

Work on wooden quadcopter from this post continues. This weeken I’ve been able to almost finish. Almost. Frame itself is done, motors and ESC are in place, electric cables soldered, but this wooden multirotor is grounded. The reason is flight controller Thunder QQ Super. Why? Because it is crap. Really. The first unit was broken and 2 motor channels were not working. Fine, it happens. Seller has sent me second unit. It arrived few weeks ago, but I never had time to check it.

Yesterday I finally connected second Thunder QQ Super to radio receiver and motors. And what? One of the motors is not spinning. ESC is only beeping and this is all. After connecting this ESC to radio RX directly, motor spins just fine. There are also no problems with this ESC when used with different flight controller (OpenPilot CC3D). It only does not work with QQ Super. Why? No idea.

OK, this time it’s not 100% Thunder QQ Super fault. It is more like incompability. But very frustrating incompability. Either way, new flight controller should be on its way and in 2 weeks my quadcopter from wood should be fully operational.

Wooded quadcopter almost done

wooden quad frame on scale

wooden quad frame on scale

wooden frame

plywood central platform

ESC on wooden arm

I must say I’m happy with results. Frame is lighter than I expected and itself it weights only 256g. With motors and propellers, weight goes up to 615g and 1100g with ESC and battery. So, it’s not light, but not so heavy after all. And it’s very rigid.

Dimensions:

  • motor to motor diagonal: 500mm,
  • motor to motor front arms: 370mm,
  • motor to motor rear arms: 300mm,
  • frame weight: 256g

And it finally has an official name: DeadRat.Why DeadRat? Because it’s a dead cat frame type and we have a pet rat. And my older daughter likes the name very much.