Introduction: Build Your Own Quadcopter
To build your own quadcopter you will need the following:
Carbon tubing - 10 mil diameter
Fiber glass fabric
Expoxy finishing liquid
Expoxy based glue
4 Brushless Motors
4 ESC's - (Electronic Speed Controllers)
1 Lipo Battery - I used a 3 cell one, think you can get up to 5 cell's
1 UBEC - if ESC's don't come with one (I kind of regulator that doesn't eat up power)
1 Flight Controller circuit board
1 Power distribution board or just make one - (I made one with some strip board and some high gauge wire)
1 Flight controller/transmitter and a receiver
Soldering iron - better to be quite high wattage as fast hot solders are better than slow cold solders
Heat Shrink to cover up electronics
Connectors for power
Connectors for Signal wires etc
Some wire probably
Mounting screws for PCP
Sticky back velcro
A Lipo battery charger
A computer for uploading settings to the flight controller and for flashing the esc's
Step 1: Build the Body of the Frame and Install the Carbon Arms
Cut a peace of bulsa wood to the size you want for your frame. The size is up to you, but I made mine rectangular so that I could mount the flight controller in the centre without needing to drill through the carbon rods. The length of the arms is also up to you but I cut the piece I had into four equal lengths. It important that you ensure that they are the same lengths if you want the thing to fly properly. They also need to be long enough for the propellers to fit the frame without hitting anything.
Mark out 45% angles where you want your arms to fit into the frame. Use a stanley knife to cut along the outer lines 5mm each side of the main diagonals as show then cut an trench out with a small chisel about 10mm deep.
Round the edges slightly with sand paper and glue in the arms with an epoxy based glue as it seems to be quite strong. Turn it over and place on a flat surface, I used an old tile. This is important as we want to ensure that all the arms are level with the base. If one is higher than the others or something expect the copter to spin out of control. Leave it for 20 mins or so for the glue to set.
Step 2: Fibreglass the Frame
Cut the fibreglass sheet to fit the frame ensuring you have a little extra which can be trimmed off later. Take your bottles of finishing epoxy resin and mix equal quantities of the hardener and resin. I used a glass jar to mix in as the heat generated by the chemical reaction can cause plastic containers melt. I used a resin with 20 minute setting time to ensure that it would not set too fast while I was still working on it.
First give the bulsa wood a coat of resin and then lay the fibreglass sheet over it, put a blob more into the centre and spread with a brush to outwards to get a smooth finish. Use a cheap brush you don't mind throwing away afterwards - the resin will make the brush stiff and unusable.
Do a few coats - I did 2, 3 or 4 would make it even stronger.
Leave to stand for 10 mins until it starts to set, trim off the excess and then use a bit more resin to brush it flat and ensure that it wraps the arms slightly to give it extra strength.
Leave it to set for another 10 mins or until it is dry to the touch and do the same other top side.
Leave to dry
Remember that working with resin and fibreglass is a sticky business and can irritate the skin - use rubber gloves.
Step 3: Make and Attach the Motor Mounts
Check your frame arms are level with a spirit level ensuring that the floor is also level. Rotate the frame and place on the top of the two legs at the top as shown in the picture. Use a file to take any excess length off the longer arms until it is level all the way around. We want to ensure that each arm is the right length so the vehicle will be balanced when we attach the motors and propellers.
Cut 4 small rectangular pieces of ply to mount the motors, try to ensure you have space to mount the motor and also some the feet as shown. I found some feet from a hardware store which are probably designed for something else, but improvise how you see fit. They are needed to keep the quadcopter off the floor, try to ensure they are long enough so that you can mount the battery onto the underside of the quadcopter without it hitting the floor.
Drill 4 holes in each piece of ply to mount the motors - you will need to measure the hole spacing carefully and try attaching the motors to make sure the holes are in the right place. Unfortunately, on the motors I had the holes were not squarely placed and I had to drag the drill about a bit making some of the holes oblong rather than round until the motors could be fitted. This is rather annoying, you may have more luck than i did with this.
Drill another hole to mount for the feet as shown, draw around the feet to ensure clearance when attaching to the arms. Remove the feet again.
Find something flat to place the quadcopter on including the arms and feet. I found a top from an old piece of furniture that was just about big enough. Use the epoxy glue to carefully connect the feet and place the entire frame on the flat surface as shown. Carefully align each mount so that it is in line with the arms as best as you can. Leave to let the glue set.
Wrap small pieces of fibreglass sheet around each mounting and paste on more finishing epoxy. This is a bit of a messy process and hard to do a nice job of, but just take your time and get each mount nicely bound to the arms.
Leave over night to ensure everything is set.
Step 4: Finnish Off the Frame
Once dry, sand the frame and mount bindings with sand paper, use sanding bits for a power drill for the bigger bumps. Try not to sand too deep as you don't want to cut into the fibreglass sheet. Just sand enough to take off the excess resin.
If you are a perfectionist and you want it perfectly smooth, you can use layers of putty and primer and keep sanding out the bumps, but I didn't bother with all that.
Spray paint a base coat and paint on any design you like. In my case I used an old bit of net curtain to spay a pattern in green over black. I also sprayed the front to arms with the brighter green and then used the stencil in reverse to blend it into the frame. This is really just so that it is easier to tell the front from the back. You might choose a bright red or something to make them stand out even better?
Although rather a lazy paint job, the net curtain left a snake skin like effect which is good enough for me.
Step 5: Mount the Flight Controller
Carefully measure the centre of the frame and the spacing between the screw holes on your flight controller board. Try to get it as square and central as possible because the flight controller has a giro on it that it uses to measure the orientation of the quadcopter during flight. Drill holes and mount with nuts and bolts, I found some nylon nuts and bolts which work well. I used two bolts on each to allow for spacing between the PCB and the frame - fixing the first screw under the PCB and the second above it.
Step 6: Sort Out Power
Normally one would have a power distribution board, but I thought I would just build my own. Not a very tidy solution, but it seems to work ok. You might prefer to buy one, they are quite cheep I think and usually have the same kind of form factor as the flight controller, so you can probably mount it with the flight controller.
I used a piece of strip board and soldered on bits of quite high gauge wire suitable for the kind of amperage required for the motors. I also added extra solder to the board to make thick tracks, which is messy but ensures that more current can pass easily. I'm not sure of the exact spec for the wire, but I would just say thick for power and thin for signals. You might want to use a multimeter to check for shorts before you plug in the battery, I used the beeper function but if you don't have that you can check the ohms. Basically you want to check all the red wires are connected to each other and all the black wires are connected together and finally that the red and black wires are not connected to each other. I soldered on battery connectors - 4 for each motor and 1 for input from the battery. I used used some shrink wrap to protect the wires. You could solder wires directly to the ESC's but I wanted to be able to easily connect and disconnect things.
I also soldered on the UBEC. A UBEC is essentially a regulator that pulls 5 volts from your higher voltage LIPO battery. In my case the battery is about 11.8 volts with a 3 cell LIPO. You can get 4 or 5 cell LIPO batteries depending on your requirements, bigger motors might want more power, but remember you will also be adding extra bulk and weight to your build. The main difference from a normal regulator is that a UBEC uses a clock pulse to pull the required voltage and then smooth out the resulting DC signal. A regular regulator is not recommended as it will hog all the voltage from the battery and waste what it doesn't use in heat - not so bad if you plug things into the mains, but really not a good idea to connect them to your battery. While I was waiting for my UBEC to be delivered I did make a little circuit with a normal regulator on it and a 9v battery to supply the flight controller and receiver with the required 5v voltage - it works for a short time but drains the 9v very fast and is not ideal.
You will also need a charger for your LIPO battery - use should really have a protective fireproof jacket for the battery as they can burst into flames if damaged or faulty. I don't have one, so I just make sure I charge it from an outside socket so it's less likely I'll burn the house down if it does catch fire - not recommended. Another warning would be if you want to take a LIPO on an airplane - make sure that you put it in your hand luggage and that the airline allows you to take them. Putting them in main luggage under the plane would subject them to dangerous pressures and temperature drops that will cause them to explode - be warned!
Step 7: Complete Your Build
The flight controller will have connections for controlling the motors and receiving control channel signals from the receiver. You may have to solder on your own pins to the flight controller and refer to the manual or schematics on the internet if you don't have a manual which is more often the case unfortunately.
There are various new standards for signals, such as multi-shot, d-shot, ppm etc. But the most basic is PWM - pulse width modulation. The basic idea is that the pulse is in the form of a square wave with a specific wavelength. The width of the high vs low signal will dictate how fast each motor should go if it is an output from the flight controller, or the position of the joystick nobs on the controller that are picked up by the receiver. I used PPM which combines PWM signals for all channels into a single line. This just means that you need less wires from your receiver to your flight controller.
Each output PWM signal from the flight controller goes to the signal wires of the electronics speed controllers - ESC's. You may also like to wire up the ground pins, some people say you don't need to as the common ground is already provided from the motor power wires. But if you are trying to configure your ESC's from your computer without plugging in the battery, then it I think you should probably have the ground signals as well.
The ESC's have inputs for the higher voltage to drive the motor coils and also a signal wire for the PWM signal, the job of the ESC is to translate the input PWM signal into a set of pulses for the motor coils. The motors have 3 motor wires each 120 degrees out of phase. The ESC is a clever piece of hardware that also reads the back EMF (electro motive force) from the coils that are not active in order to determine the direction and position of the motor. Usually you need to set up the ESC's with the relevant firmware depending on the manufacturer and associated software - most use B-Helli or SimonK to configure the firmware, but mine was by Gemfan who have their own software package. You will need to research your particular ESC. Many allow you to set the direction of each motor in the firmware as well, but if not you just need to switch any two of the three motor wires and solder it again to change the motor direction.
Unfortunately most of the ESC firmware configurators only run on windows - which wasn't ideal for me as a Mac owner, I had to install a virtual machine with windows on it just to set the ESC's up - really annoying, but at least it worked in the end.
For more advance flight controller settings there are various choices including betaflight, baseflight, cleanflight and raceflight. The software for these are open source so you can look at how they work if you like or even contribute and make changes - if you are that way inclined. Personally I've not tried to change anything but I've learned quite a bit about STM32 micro-controllers from reading the source code. The software usually comes in two parts one part is the firmware for the flight controller the other part is the configurator, which mostly run as chrome extensions and so are platform independent so long as you have Google Chrome installed. The configurator is used to set up your various settings for the flight controller and install them on the flight controller. Before you configure your motors - please - please - make sure you remove the propellers to save yourself from a nasty propeller in the face accident. The best way to learn about configuring your flight controller is really just to install one of the configuration tools as a chrome extension and read around it as much as possible on the internet.
The basic steps are to set up your ESC's and make sure all the motors are turning in the correct direction. Two clockwise and two anticlockwise alternately on a quadcopter but the configuration tools have diagrams with the correct directions for each motor - the same goes for the propellors, two clockwise, two anticlockwise props.
You want ensure you are getting signals from your receiver for the joysticks and for the switches - you can set ranges on the multi-select switches for different operations, I just use one to arm the quad at the moment, but you can set up different flight modes etc.
Another thing I set was a dead band range for the centre positions of the sticks, primary because I had a problem with yaw on a previous build where it span out of control - although I think it was more likely to do with a wonky/twisted arms - hence the reason for this tutorial - a few failed attempts. The dead band is just a range from the middle position that the controller will ignore and treat as centre, this means a slight inaccuracy in the signal from the receiver wont make the controller think you are trying to turn left or right when in fact your sticks are in the middle position.
Also set the min and max throttle ranges for the motors - A good rule of thumb is to set the lowest level so that your motors will be spinning slightly but very slowly at the min range rather than not moving at all, then bring up the speed - (without the props on!), when it sounds like the motors are at max speed and it won't go any faster even with higher throttle, then bring down the max accordingly - this way your sticks will match the full range of speeds of the motors rather than have dead space either side that doesn't have any effect.
To attach the receivers and batteries I used combinations of sticky back velcro tape, cable-ties, and insulation tape. You may want to make a special holder for the battery? Probably a good idea if you don't want to bash it when landing hard - try to mount it centrally so that the weight of your copter is balanced.
Step 8: Fly It
Here are some test flight video's. The first is my partner having a go at flying it and doing much better than me. Then my attempt where I lose track of it and manage to lose it somewhere in the wilderness never to be found again. As you can see I cannot offer any advice on how to fly a quadcopter and you should ignore all the advice I offer my partner. I suppose in retrospect I would advice adding come kind of tracking device or adding GPS with a ground station of some sort to track it's movements. Also try to make sure the battery is better housed so that if it does crash you have a chance of it still working enough to receive a signal, perhaps giving it a little throttle to see if it pops up or if you can hear it? Oh well you live and learn, this was rather an expensive experiment but I still enjoyed the process of building it and actually getting it to work - if only for a short period.