QAV250 Xmas build a'la banggood.com

Long time no post as usual but this fall hasn't yielded a lot of building worth posting. This however is a complete QAV250 build with most parts from the cheap Chinese online shop banggood.com.
Parts needed are the usual suspects starting with the frame. This is a carbon fiber/plastic frame with a robust X shape for $16.99. Just be careful and use lock-tight to keep screws in place.

This combo package consists of an ESC, a brush-less motor with a 5x3 propeller. The ESC is programmed with a SimonK firmware, which is something to aim for as his firmware usually does a better job than the stock firmware. Motors are 1804-2400kv from ZMR. This package goes for $16.08.

One motor was broken on delivery. It felt like one of the magnets had come loose and I've heard from others that they have had similar problems too. Luckily, I bought one spare package.

As flight controller, I'm using a Naze32 copy called Flip32. It's based on a 32-bit ARM Cortex-M3 processor (STM32F103CB). It can be used with both Baseflight and Cleanflight, which are both open source projects. I'm using Cleanflight as it feels newer and seems to have a more active development. It also has a few more features, such as Autotune. PID configuration can be used right out of the box.
Note: One issue I experienced is how to arm the flight controller. After some research, I figured that you absolutely need to calibrate both magnetometer and accelerator in order to get it to arm. $24.59.

I'm using a generic 1300mAh battery, which is common with QAV250 models. I have had no issues with these batteries so far. $20.45 each, I bought two but I think that I'm going to order a couple more.

Radio receiver is actually bought from Hobby King rather than from banggood, simply because I fancy the OrangeRX brand. It's a seven channel RX with fail-safe functionality. When used properly, if the RX detects a loss or radio connectivity, it'll automatically pull down the throttle channel to a minimum. This will prevent your model from flying away. If you're interested in the "fly away" topic, do query YouTube with the keywords "quadcopter fly away". $17.99.


Merry Christmas and fly safe!

A new era, a new beginning

It's been a while since my last post. The main cause is that I felt the energy drain as the fall gets more visible with worse weather, not too encouraging for quad flights. The darkness is also upon us, which makes flight difficult if it's not during day time.

As I've previously written, I ordered the radio telemetry, which I now got working. No hassle, it worked instantly. The only fault I did was to not turn down the COM-port speed from 115k to 57k, there after it worked as a charm :). The picture displays how the flight controller is connected to the laptop and Mission Planner using the radios. The radios are basically a wireless serial port.

 

Next, I focused on the darkness or rather how to fly when it's not full day light. Dusk has previously also been a hassle but these lights should mitigate that obstacle. Looking close at the picture below you can see how I wired the break out wire directly to the power distribution board. The board has tiny connectors all over, which allows soldering and therefore can provide extra connectivity as these lights require 11V.

 

Now to the final product, I started putting the quad back together, putting the lights in place. Hope this can light up any future winter flights.

I decided to go with green on the front and red on the back. Traditionally you should have green to the left and red to the right, but that doesn't help me when I usually see the quad from behind. Therefore I went with red to back and green up front.

 

MegapirateNG vs. MultiWii

I've been reading up on forums on the progress of future releases for the MegaPirateNG code base. To my astonishment I soon found out that the main maintainer behind MegaPirateNG left the project to join the ArduPilot team. This means that currently MegaPirateNG isn't developed. A small project fork all tho seem to have been done by some enthusiasts. This is called megapirateng-add-ons ( https://code.google.com/p/megapirateng-add-ons/ ) and is a beta into MegaPirateNG 2.9.1. Some folks claim its superb while some clam it has serious bugs. Others tell to look into the MultiWii code base instead.

Today I tried out the MultiWii 2.2 code, which is the latest in it's branch. From the first look and feel, it feels like the quad is handling a lot more stable. This is before touching any PID parameter configurations. I've done some level flights and it feels really stable. I haven't figured out if it's possible to configure the controller to decelerate the quad on releasing any of the pitch or roll controls, which MegaPirate did by default. That behavior is very helpful for beginners.

The guide I used to get going with MultiWii can be obtained from this forum thread:
http://www.multi-rotor.co.uk/index.php?topic=411.0

This is my current configuration and a look at the MultiWii configuration program.

One detail I found very useful is the fully configurable mode selector. This can be used to combine several features to build your own flight modes instead of having to use any vendor supplied modes.

My configuration states that not using AUX1 should result in a level (angle) flight. Using AUX1, level, barometer to hold altitude, magnetometer to hold heading and GPS to hold position should be used. AUX3 is used in a similar fashion but invoking GPS return to home instead.

It's thereby possible to combine any of these features in any desired way. Further explanation can be obtained at the MultiWii wiki page.

Stay tuned for more information as I go along. I will try to test out the GPS return to home function rather soon.

Whats broken

 

Today's casualties:

• Bottom right boom was bent
• Propellers spent as you can see
• One motor with strange sounds
• Ultrasonic range finder is MIA
• Few nuts and buts are spent

I found all electronics including flight controller, GPS, radio and ESC's to seem to work as usual.

Next thing I'll buy is the telemetry radio :).

More electronics

Doing some further research found that HobbyKing also features the 433MHz telemetry kit I found at GLB (GoodLuckBuy.com). Link to mentioned kit.

However, this kit comes with antennas that are optimized for 900MHz rather than 433MHz according to comments. Seem to be the same transmitter and receiver anyhow so if I choose to buy these, it will be from GLB.

Further browsing, I found a flight controller resembling the MultiWii/MegaPirate controller I previously used. This controller claims to be version 3 and seem to have improvements in the way the serial ports are made. Version 2 had three serial ports in the same physical port when this controller has separate physical ports for each serial port. I can't see any other differences looking at chip specifications.

MultiWii & MegaPirate v2.0

MWC Mega 3.0

If I can find that these are compatible, I'd rather choose the version 3 as soldering small wires are a pain when breaking out the serial ports.

Ultrasonic range finder part II: how it works

The now famous URF (ultrasonic range finder) has a bit more to tell than I wrote in my last post. One of my big questions was how it would interact with the on-board barometer. As any technical person would understand, is that at some point there will be some kind of conflict as these sensors will indicate different measures.

The URF is rather exact but only has a range of five meters. The barometer on the other hand has unlimited range but isn't that exact. In fact, its quite noisy and differ +/- 1-2 meters.

My experience is that the flight controller handles this in the way that, if the URF indicates different than last measurement then, it's the current height. Otherwise, the barometer is used. This way the URF is disregarded if it's too far from any object and the barometer takes over but also acts as an anti-collision sensor when coming in proximity to the ground.

What I'm still to experience is: What happens if the quad flies over trees? The barometer may indicate 20 meters, while the URF suddenly indicates 3 meters. What happens if it's programmed to hold at 20 meters? Does the quad bounce up 17 meters further? Interesting question.

Issues that I've experienced installing the sensor is that on my device, the Echo and Trigger labels are the wrong way around. On the flight controller that I'm using, the Multiwii MegaPirate board I'm supposed to connect echo to pin 9 and trigger to pin 10. That didn't work unless I connected them the other way around ;).

It became self aware

Someone once said: -"Pictures or it didn't happen".

This is how to get prepared for flight. In addition to the quad and the transmitter, you need a laptop.

Everything is by this time wired. That's why you see the green light on the flight controller. It indicates that the GPS reports that it is locked on to a fixed position. The sonar is also connected and reports correctly.

 

Another picture..

So, you wanna see how it flies :) ? The video is rather short due to two factors.

• The battery of my mobile was at this time drained to 4%, hence keeping it short.
• The left down motor gets seriously overheated due to some fault. It may break down if its magnets gets loose. This could happen due to heat as they are glued on...

 Note that I show no hands as the quad loiters :)

Cirus All-In-One Multiwii and MegaPirage flight controller

Today I made my first firmware build and fired up the Multiwii flight controller for the first timer. Here is a small sample of the feedback I got when I tried it out.

Only a short update today as I haven't been up to a lot yet other than this. I need to buy some "helping hands" in to start soldering connectors onto those ESC's. It's a common tool used when soldering as you often need a pair of extra hands. You can buy them online at Banggood but I think I'll buy them at a local hardware store as they don't cost much more over here.

Schematic drawing

This is the way that I see that my quad will be hooked up. As I'm new at this, I will keep this drawing up to date as well over time.