TX: Turnigy 9XR or FrSky Taranis (more expensive, but a good investment since you probably won't crash this one...)
Frame: any 330 size frame will do. This one for instance: https://www.banggood.com/DJI-F330-4-Axis-RC-Quadcopter-Frame...
Motors: 2212, ca 1000kv will make it pretty sporty
ESC: 30A
This combo set is only 19 bucks: https://www.banggood.com/XXD-2212-MotorZTW-AL30A-Brushless-E...
Flight controller: Naze32 or CCD3. Doesn't really matter. This one is fine (it's in my latest quad) and is only 11 bucks: https://www.banggood.com/DALRC-NAZE32-REV6-MPU6050-32-bit-6-...
You'll need extra props, wire and nuts and bolts. 400 dollars is totally achievable!
Not a lot of success on the big one - before FPV it was notoriously hard to fly, and after FPV it turned out it was unstable on sharp turns (see crash videos). Haven't gotten around building a next iteration. Latest one is a aluminium-plastic frame, 2825-1100 motors, 3.5Ah 3S battery, about 1.5Kg weight. Nicknamed flying guillotine due to it's bush-chopping 10x3.8 props.
The small one ("Acro") performs very well as an indoors/training quad. 3D printed frame, 800mAh battery, 1811-2000 motors, about 300g weight. Held together with zip ties across stress points, with connections angled as to be flexible on impact but lock solid under static load. So, you can crash it all day long and only need to replace the zip ties or props occasionally.
All had custom flight controllers and software, no ideas on that front. Not sure about the prices, since all the core parts were bought years ago.
If you think it'll help you decide on beginner-friendly parts, here's the kit we use. This is in no way intended for racing, but this will put someone in the air that wants to get into the hobby.
For a flight controller, we use KK.2s [2] and CC3Ds [3]. The KK.2 board is programmed through a built-in screen, so it's useful if you want to make changes on the fly (no pun intended). The CC3D is tuned by plugging it into a computer running LibrePilot [4][5]. The advantage to that is that LibrePilot gives you much more features/customization options than the KK.2's tiny screen does. I've also found the CC3D to be a little more reliable.
Our transmitter/receiver combo is the FS-i6 w/ the FS-iA6B [6]. Nothing special, should give you about a half-kilometer of range. If you're willing to spend a bit more, I highly recommend the Turnigy Evolution [7]. It has much nicer gimbals, and feels a lot more comfortable in the hand. The only disadvantage you'd have with this one is that switches/knobs are limited, so if you want to make cool peripherals you'll have less options (fun fact- if you hook up directly to a channel output on a receiver, and bind that channel to a switch on a transmitter, the servo will move in either direction! Lots of cool things you can do with that)
For motors/ESCs, this MultiStar motor/Afro ESC combo pack [8] is pretty nice. The motors can break if crash hard, but the hardware you get for the price is excellent. If you get them, heads up: the axle that rotates with the motor sticks out to be lower than the base of the motor, so when you mount it, make sure that it won't drag on anything when it spins. Most frames have a hole for this purpose, but I've had issues with this in the past.
When you're not racing, propellers aren't something you can go wrong with (well, at least compared to other parts). With your price range and the assumption that you're just building a simple multicopter for flying in a field somewhere, 6-inch props (Example [9]) are really all you need.
Batteries are something that really depend on what kind of flying you're doing. You can go from tiny 1-cells for brushed micro quads [10] to high-discharge 4-cells for racing [11], all the way to massive 30,000 mAh LiPos for, I don't know, agriculture or something? [12] I'll have to make guesses about what kind of drone you want to build, but unless you're doing something extreme, a simple 3-cell 1500 mAh LiPo should work fine [13].
As for a frame, I recommend you 3D print one if you're not racing or trying to do acro flying. There are a million on Thingiverse, but there's one called the Crossfire that I really like [14].
Again, I have no idea what kind of multicopter you're trying to build, and there are so many ways that the parts list would change if you were trying to get into racing or full autonomy or something else. Other than the frame, this is what we start kids off with, and it's proven to be an effective way to get people into the hobby.
[1] https://www.g3robotics.com/dfg [2] https://hobbyking.com/en_us/hobbyking-kk2-1-5-multi-rotor-lc... [3] http://www.getfpv.com/openpilot-cc3d-flight-controller-strai... [4] https://www.librepilot.org [5] https://github.com/librepilot [6] https://www.getfpv.com/flysky-fs-i6-afhds-6ch-transmitter-an... [7] https://hobbyking.com/en_us/fpv-racer-radio-mode-2-white.htm... [8] https://hobbyking.com/en_us/multistar-afro-combo-pack-2206-b... [9] https://hobbyking.com/en_us/gemfan-propeller-6x4-5-black-cw-... [10] https://www.getfpv.com/tattu-220mah-3-7v-45c-1s1p-lipo-batte... [11] https://www.getfpv.com/lumenier-1300mah-4s-60c-lipo-battery-... [12] https://www.genstattu.com/tattu-30000mah-22-2v-25c-6s1p-lipo... [13] https://hobbyking.com/en_us/zippy-compact-1500mah-3s-25c-lip...
Side note, this is my first post to HN. I have no idea what I'm doing, and if I'm breaking any unwritten rules or something please tell me! Thanks
The first iteration of the flight controller consisted of an Arduino nano, MPU9250 breakout board and ESP8266 for WiFi communication (I've intended to use an Android app for control): http://imgur.com/NyHABh7 (the Arduino nano and the MPU9250 breakout board are missing because I'm using them in the new board)
This setup never took off because of two main things: 1. The Arduino proved to be very slow. (8 bit without FPU) 2. The Android controllers on the touch screen made it very to control the drone.
So, I decided to "gut" a toy drone controller put an Arudino + nRF24 in it. And since I now needed to replace ESP8266 with an nRF24 and replace the Arduino nano with something more powerful, I built a new flight controller with both the nRF24 and a Teensy 3.5 (which is an ARM with Ardunio compatible libraries): http://imgur.com/XtaDUPi The controller: http://imgur.com/8Br1cMs http://imgur.com/cY1FupV http://imgur.com/sJyS0EJ
And this time the drone actually took off! And after a lot of PID tuning and messing around with the algorithms it actually stayed in the air! (I'll upload a video later, I can't take one now because it's 1am...)
But the controlls were still pretty bad. They we're very sensitive and noisy. Since I enjoyed this project (both building/coding and flying) so much, I decided to take it to the next level. I bought a real flight controller (Taranis X9D) with a compatible receiver, and instead of building another new flight-controller on a proto-board again, I made a PCB: http://imgur.com/08oFkGW
Here's the PCB actually sitting on the drone right now: http://imgur.com/KqvGPd5 http://imgur.com/Svjz61w http://imgur.com/jerlNHB
Currently I'm working on the next version of the PCB with a few fixes, and additional magnetomter and a barometer: http://imgur.com/nqLHzKc
If there's an interest I'll make the source code and PCB layout+schematic open source. Sorry for the poor quality of the pictures, and a lack of video of the thing actually flying :). I'll take some more pictures and videos tommorow hopefully :)
