Quad Copter UAV Project

In late June I was finally convinced by a friend to get involved with his RC (Radio Controlled) helicopter hobby. He had been involved on and off since we were kids, while I’d always been much more interested in programming computers. Now the technology of the two hobbies has come together and he’s finally convinced me to get involved.

He recommended I buy four items, to have a good starter system. I bought the first item, and spent a month trying to figure things out, and then bought the rest of the items. I would have been better off to have simply spent all the money he suggested up front, as I didn’t like trying to fly the original UAV at all. If I had more experience flying RC airplanes my experience might have been different, but without the computer controlled stabilization, I really did not like the experience of flying the quadcopter at all.

• AeroSky Radio Remote Control RC Quadcopter  4 Channel RTF w/ LED (Red)
• 915Mhz ArduFlyer-UAV GPS Flight Control System
• APM 2.5 Case (Cables enter from side)
• APM Power Module with Deans Connectors Kit

The first item is described as Ready To Fly (RTF.) It is delivered with everything needed to fly except for 8 AA Batteries for the RC Transmitter.

• Pre-assembled Four Arm Flight Frame
• 4 Propellers
• MWC Flight Control Board
• ESC: Four 40A Brushless Hobbywing SkyWalker Electronic Speed Controllers
• Motor: Four 2212 OutRunner Brushless 920KV Motors
• 2.4ghz 6ch TX and RX
• Battery 11.1v 2200mah 20C Li-Po
• 3cell Balance Charger

There are also kits described as ARTF, which means Almost Ready to Fly.  The ARTF kits cost around $40 less and don’t include the RC receiver, transmitter (RX, TX), LiPo battery or battery charger. Since I didn’t already have a RX/TX pair, having the entire package together was certainly worth the $40 price difference. An average price for a similar LiPo battery alone would be $15.

A significant portion of time in researching what I wanted to do was spent in learning the terminology and acronyms. Actually having the device in my hands has helped me to understand what each part is and what it does.

AeroSky Radio Remote Control RC Quadcopter 4 Channel RTF

The first thing is that the assembly instructions were extremely sparse. An experienced pilot might have no problems, but I certainly didn’t know what I was doing. The second thing is that while it ships with a Balanced Battery Charger, the only way of supplying power to the charger is a cable with a set of alligator clips.

There was no mention of what the extra wires in the bag were for. I later learned that it’s a special wire to be used for calibrating the four Electronic Speed Controllers (ESCs.) When I opened the box I had no idea what an ESC was, or that it might need calibration.

There are two bags of colored propellers. Each one is a set of two, that are designed to provide lift when rotating in opposite directions. The props need to be installed in a specific orientation for the device to have any stability. Forward Right rotates Counter Clockwise, Forward Left Clockwise, Rear Left Counter Clockwise, Rear Right Clockwise.  The propellers come with a set of nylon washers to fit various sized shafts. Using the washers that fit the tightest is important. Tightening the nuts and using so sort of lock tight solution is also recommended, especially because with the counter rotating shafts the nuts naturally want to spin free.

The radio controller transmitter that was shipped to me is branded Aerosky Digital Proportional Radio System 2.4 GHz FHSS Airplane System. The only unique labeling on the back was: Model MC6S and the FCC ID: ZMKMC4DFMCD6DF.

Aerosky Digital Proportional Radio System 2.4 GHz FHSS Airplane System

Aerosky Digital Proportional Radio System 2.4 GHz FHSS Airplane System

Aerosky Digital Proportional Radio System 2.4 GHz FHSS Airplane System

The rear view shows an audio style plug labeled D.S.C. and the side view has an unlabeled power plug. There is a small wire wrapped around the top handle of the transmitter. I have learned that this wire is a Bind Plug that can be used if my transmitter and receiver are not correctly talking with each other.  The receiver has a seventh set of pins that I’m supposed to plug this into and then I can bind the receiver to this transmitter. I’ve not found instructions for this radio anywhere on the web that confirm exactly what I’m supposed to do, but I’ve at least learned what binding is from other pages on the web.

The battery charger is labeled BC-3S10 2S/3S Balance Charger. It lists DC 9V-16V with center pin positive on the input side, and has two outputs, labeled 3S(11.1V) and 2S(7.4V). I had a AC Adapter from an old computer with a compatible plug and an output description 12-14V 5-4.28A that I was able to use to power the charger. When plugged in, the charger has two LEDs labeled Power and Charge. The Charge LED appears to blink until the battery is fully charged, and then goes solid.

When a battery is plugged into the UAV there are a series of beeps that happen. Three ascending tones, a pause, and then a pair of tones. The LEDs that are installed completely wrapping each of the arms also light up immediately when the power is supplied. I’ve learned that the tones are generated by the ESCs, so when you hear the tones, you are hearing four separate devices chirping at the same time, not related to signals from the central controller board. In this ready to fly package, the ESCs are presoldered to a control board, so there is no way to power them separately. If the boards need to be re calibrated for some reason, the beep tones may be different, and recognizing which arm is doing the beeping can be incredibly difficult.

My first day flying the unit in the RTF configuration I never felt comfortable flying, and I ran it into a stone retaining wall. When I ran it into the wall and crashed, I only chipped the end of a propeller blade slightly and broke the continuity on one of the LED strips, making one of the arms have an intermittent set of LED lights. The unit itself seems to be extremely durable.

After a couple weeks of not feeling happy with the stability and my flying ability I ordered the other items in the parts list. The flight control system I am using is produced in China by RCTimer and is a third party imitation of the ArduPilot Mega 2.5 Auto Pilot. The RCTimer package includes the GPS and Ground Control Telemetry Set that bring the 3DRobotics price up to $250. By buying the RCTimer package I had to buy the APM Power module and Case separately, and solder a huge number of header pins onto a circut board. I save $75 but I spent a huge amount of effort getting the soldering done. I’m not certain which way I’d go if I was doing it again.

I will generally refer to the flight control board as APM because that’s the term it is easiest to refer to it as when searching support forums. The original control board was referred to as MWC, which I’ve learned stands for Multi-Wii-Controller. It’s original heritage came from hobbyists reverse engineering the Nintendo Wii game console controller to learn how to use its accelerators.

The MWC that was the heart of the original RTF package was completely removed and the APM replaced it. The control wires from the RC RX unit connect to the APM inputs and the control wires to the ESCs connect to the outputs.  The APM has three other sets of external connections, Power, GPS, and Telemetry.

The two largest features of the APM that I currently use over the MWC are LOITER and RTL. I have switch 5 on my transmitter set to switch between Stabilized Flight Mode, and Loiter Mode. In Loiter mode, the UAV will will hold position in the air solidly.  I have switch 6 set to RTL, Return To Launch. RTL will rise to a set altitude, move to the GPS location the UAV took off, and then descend to the ground. Having these two features available has allowed me to learn how to manually fly the unit without constantly crashing.

I did not know anything about arming or disarming the ESCs when I started this process. Now it seems intuitive, but it was just one more thing I had to learn when I started. The motors will not turn under power until the ESCs have been armed. This is a protective feature because the blades will easily harm you if you are in their path. To arm the motors, you hold the throttle down to zero, and the stick to the right for a period of time. To disarm hold down and to the left for a period.  With my APM controller I need to hold it for ten seconds to arm, and 3 seconds to disarm, I don’t know if the APM is managing that detail or if it’s simply passing the signals directly to the individual ESCs.

Successful Evening Flying