As I said in my previous post, I’m going to chronicle my quadcopter build. I’ve never done this before so I expect to make some mistakes. Hopefully I can learn from others and keep those to a minimum while learning lots of things along the way.
The first quad I’ve decided to build is going to be focused on photography. I’m looking for still and video pictures taken from the perspective of the quad. I want to try to keep the weight below 1000g total and I think this will do it. Here is the quad I’ve designed so far and what I’ve purchased:
Frame: Turnigy Talon v2, Carbon Fiber, 550mm, 280g, $50
Why: I wanted a decent size frame to maximize stability. I’m not interested in aerobatics with this quad, so a big frame is the way to go. I also wanted to minimize the weight of the frame. I’ve read the stories of many others making frames from aluminum, wood, etc. and finding they were just too heavy. Hopefully this will do the trick.
Where: I purchased this frame from hobbyking because they had a great price for a carbon fiber frame ($50) and because I was ordering some other items from them at the same time.
Flight Controller: ArduPilot Mega 2.5+ with , 21g, $180
Why: Ultimately I want a craft that can handle autonomous flight. While I’m sure I’ll have fun manually controlling the copter I am most interested in building a drone. I’m looking for a device that can fly itself and take photos/video. In Jan 2013, this is the controller to use if you’re interested in that. While there are other controllers that are cheaper, I don’t think any of them possessed the software and community that this does. The ArduPilot Mega contains an ATMEGA2560 Arduino Mega. It also includes a ton of useful modules including a 3-axis gyro, accelerometer, high resolution altimeter, magnetometer (aka digital compass), and an off-board Mediatek GPS. There is an option to deliver telemetry data via an XBee radio module to a laptop but I didn’t choose to buy that yet. I figure that if I want it later, I can always order it as an add-on ($40).
Where: I ordered this from the source – 3drobotics.com. There is a way to order it for less if you’re willing to do more work in terms of soldering and buying the connectors yourself – rctimer.com has one for $140.
Flight Controller-add on: LV-MaxSonar-EZ0, 4.3g, $30.
Why: I decided to add on the sonar module after reading about how you can use it to let the craft land itself. The ArduPilot contains an altimeter that allows it to detect its height, however that device is unusable below 10 feet. In order to fly and land safely a sonar module is used to get accurate height data and allow ‘nap of the earth’ style flight. That said, I also read plenty of posts about these things not working right all the time. It seems the device can be noisy in that its data feed contains some bad data while flying over uneven terrain like grass (versus smooth pavement.) We’ll see!
Where: I got this when I purchased the flight controller from 3drobotics.com.
Motor: 4 x NTM 28-30A 750kv / 140w, 67g each, $15 each
Why: I wanted motors that were proven but could be had for a reasonable price. After the props, these parts are the ones that are most likely to break in a crash. And while I hope I can keep that to a minimum, I know this is going to crash. I picked these after reading some people being happy with them and using a tool to determine if 4 750kv motors would provide enough lift. I want to have room to spare in case I wan to put on a relatively heavy camera.
Where: I ordered these from hobbyking.com while ordering most of the other parts. Luckily these parts were in the US warehouse in Seattle meaning I could keep the shipping costs down (shipping from China is more expensive than I expected.) I ordered 6 in order to have a couple as backups. I also ordered the accessory kit which includes the prop adapter (a collet to hold the propeller in place) and mounting brackets and screws. I don’t have data on the weight of these parts unfortunately.
Electronic Speed Controller: 4x Turnigy Plush 25A, 22g each, $13 each
Why: An RC aircraft requires a speed controller per motor that allows the flight controller to change the speed of the propeller when it needs to. The idea is simple, but apparently these little controllers are the source of much frustration. They can overheat and fail and when they do, a quadcopter is going to crash. While a fixed wing aircraft can glide down if the speed controller fails, a quadcopter can’t, obviously. The prevailing wisdom is to place these controllers out on the arm of the quad away from the heat-generating devices like the battery and flight controller. I see that many people like to ensure they are being hit by the propwash in order to cool them. There is one interesting feature to these little controllers I didn’t expect, and that is because of what they do already they include a regulated voltage output (in this case, 5V 2A) that can be used to power something else (that’s the little plug in the photo.) For fixed-wing aircraft this is normally a server to control the flaps or rudder, but on a quadcopter this isn’t that useful. I’m not sure if I’ll use this feature or not.
Where: I ordered these from hobbyking.com but they had to come from China. They were highly rated by the enthusiast community and also really cheap at $13 from hobbyking so I ordered 5 in order to have a spare. Even when I factored in the shipping cost, these units were still about 3/4 what you could buy domestically for similar quality.
Propeller: Slow Fly 10×4.5 ABS propellers, $0.77 ea
Why: Supposedly these propellers are strong plastic designed for use on electric motors. Of all the things on my quadcopter design this is the one area where I can’t tell much about strength versus weight versus balance in terms of value. I do know that I will be balancing them when they arrive but given how cheap they are I might also get some locally at a hobby shop rather than order them online in the future. Obviously the quadcopter needs 4 and I ordered a set of black and a set of red (with extras) so that I can see the orientation of the quad by putting 2 red in front and 2 black in back.
Where: I ordered these with the other parts from hobbyking.com.
Battery: Turnigy nano-tech 2200mah 3S1P LiPo, 187g, $19
Why: I read good things about these batteries and the run time some are getting from a single 3 cell battery. I also learned to purchase the nano-tech variety due to the limited swelling during use. According to one report, a traditional lithium ion batteries can increase in size by 15% due to heat during discharge. I’m not sure if I will use one battery or two during flight so I ordered 3 while I figure that up.
Where: I ordered these from hobbyking.com because it was in the US warehouse. If it had not been, I would have been looking for a local source.