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!

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 :).

Spare parts has arrived!

 

A spare HobbyKing X550 frame, which I'm going to do some DIY'ing to use to add another level/layer of stuff to my current frame. You'll see how it works out soonish.

Battery for the Turnigy transmitter and a li-po low voltage alarm. I must have misplaced my other alarm I ordered a while ago because I can't find it. This alarm does both show the level of charge and also sound an alarm when the charge drops below 3.3V. My ESC's are currently programmed to cut-off at 3V to not harm the battery. This will hopefully prevent any fatal crashes that could happen if the motors are cut in mid-air. Luckily, this hasn't happened yet. The only times I've encountered cut-offs are just after takeoff which resulted in a one meter free fall.

Maiden flight flipped over

Today I flew my quad for the first time. It left the ground and within less then one second flipped over..

It seems as if one of my motors isn't running correctly. Each electric motor, as most people know, consists of a number of magnets that are energised in sequence in order to turn the propeller. However, if one or more of these magnets are faulty, the propeller will not turn as intended. This is something that the motor early on indicated as the propeller seemed as if it didn't start up as early as with the other motors. I choose to ignore that and drove up the throttle, which then made the propeller turn and accelerate as the others. This then made the quad to flip over each time I tried to fly.

As this blog states, I tried to keep my budget low and to buy cheap parts. The motors I'm using are branded Turnigy. That brand is a cheap Chinese pirated copy of another brand, which also makes it less reliable. I was then also early on recommended to buy a few extra motors while ordering to be able to coupe with one of them to be broken on delivery. That I never did. So, today, I've ordered two extra motors plus two ESC's as I actually don't know if they may be faulty as well.

Another thing, I tried to mount the prop savers to the engines today to be able to save the propellers if I'd crash only to figure out that I'd ordered prop savers with the wrong dimension of the propeller shaft. Ordered 4mm prop savers now also instead of the old 3mm.

One wire too short

I've been assembling the quad today and it turns out that I'm one wrote too short, or actually a few too short. The wires from the ESC's that are to connect to the power distribution board are a few centimeters too short... This means I need to solve that before there will be any flying :(

No success without a little ooops!

Progress! I've got both radio modules talking to each other after flashing with the openLRSng firmware. I actually didn't do any changes to the default settings and it compiled without any issues. The upload of the firmware however was a bit complicated.

As I mentioned in a previous blog post, I bought a USB serial converter called CP2102. What I probably should have bought was a FTDI adapter. This adapter has a pin called DST, which is needed to auto reset the target board when the new firmware has been transferred. The CP2102 however does not provide easy access to the DST pin. The solution was, as many others have done is to do a make shift soldering on the USB adapter in order to provide access to the DST.


And, first off, I cannot take credits for this tiny soldering. It's been done by a another guy who is far better than me. The solution consists basically of connecting pin 28 from the chip in the middle to output on the RST pin. A resistor was also removed to break the RST connection to not get double signals. I actually removed the resistor and made the other soldering, which probably was way easier. Soldering the wire to the 28th pin of the chip had to be done under a microscope :).



So, now we've got a working radio link that I've verified to provide signals that work as intended. The picture below shows how I've connected the radio receiver to the power distribution board, which also connects to one of the ESC's that connects to one of the motors. I'm now in the process of programming and calibrating the ESC's. This is needed to ensure that all motors behave in the same way and provide the correct amount of power given the throttle.

Todays ooops! happened when I by accident short circuited the battery and left some ugly marks. I should have put shrink tube on the soldered connectors of the power distribution board before playing with it, but I didn't :[.

Sub projects and more

Notice the sub projects link to the right, it contains identified sub projects that need to be completed to finish the quad.

Yesterday I finished soldering all four ESC's. I've also secretly assembled the quad frame and attached it's motors. Behold for future pictures ;).

What's needed to get the radio running is 3.3v. It's specification specifies that it can receive 3.3-12v, which apparently isn't entirely true. Incidents according to forum posts where people have used one of the 5.5v outputs the radio have resulted in burnt circuits. Some people have recommended using a separate battery pack consisting of 6x AA batteries, which would provide 3.7v. Other than that, there is a 3.3v uBEC available from HobbyKing. I think I'll also arrange for a separate battery pack and maybe order the uBEC sometime in the future.

First soldering ever!

This is my first soldiering I've done as far as I know and I've done five bullet connectors without any disasters!

What I'm actually doing is soldering 3.5mm gold connectors onto one of the ESC's. This is because these ESC's as most others are delivered without any connectors. The other way would have been to solder the ESC right on to engines and power distribution board but as both those were equipped with bullet connectors, I thought it'd be wise to keep that standard. I also want to keep my model in modules so that each part is replaceable without any heavy soldering.

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.

Packages!

This is what I fetched from the post office just now. As far as I know this should be more or less it and I don't miss any vital parts.

 

About the transmitter which I thought to be less than complete, actually is complete. I've been in contract with HobbyKing and got it all cleared out. 

Now it's just to start putting things together. The first task will be soldering connectors to the electronic speed controllers (ESC). Will be back with progress..

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.