Basic Parts of a Do It Yourself Drone
Frame -Like anything that needs a rigid body to hold its weight, a drone (quadcopter) has a frame made from rigid materials to act as a backbone. Then you have other parts (electrical) that are mounted on the frame and connected by wires. We will take a closer look at the frame first.
Quadcopter (or other forms) frames come in various sizes and shapes. They also have a weight rating so you can select the one best suited to your purpose. When flying, weights take away energy so you will normally choose a frame that is light weighted but make sure it is strong enough to withstand crashing.
Most have the same basic appearance – a vague X shape or a + shape. There are two basic types, one for utility and the other for racing or for performance. If you are sourcing from the market, bear in mind the numbers given to them.
Frames are numbered from 150, 200, 500 and this number depicts the diagonal lengths from one motor to the other. Frames are normally made from carbon fibre, alloys (aluminium), plastic and glass fibre. Frames must be strong enough to hold all the components on board as well as to be able to withstand the stress arising from the movement of the drone in the air.
Not forgetting that frames must also withstand the shock from a forced landing or collision. For hobbyists wishing to mount something with additional weight such as a camera, a sturdier frame rated for more weight is recommended.
However, adding a sturdier material typically creates more weight itself, causing you to require longer propellers and a stronger motor to create the lift necessary to pull up the weight. You will definitely need to strike a delicate balance between flight speed, manoeuvrability, and flight time (a normal battery will only afford you at most a twenty minute flight time).
Motors-The next and probably most important component is the motor which will drive the drone. Motors are rated in “Kv” units, which equate to the number of revolutions per minute a motor can achieve when a 1v current is introduced to it unhindered. The higher the Kv, the faster the motor can spin.
However, faster is not always better. A faster motor spin requires much more power from the battery, causing your flight times to decrease. More power also means faster wear as it is referred to as ‘burn out’.
Motors comes in designated numbers like 3310-1000kv where 33 represents diameter size of the stator in 33 millimetres and 10 represents the height of the stator in millimetres. 1000kv represents the revolution per minute when a charge of 1 Volt is applied to it. Motors come with different bolt patterns which must be the same as that on the frame.
Propellers-Propellers largely affect the speed at which the quadcopters fly, the load that they can carry, and the speed at which they can manoeuvre and they all are similarly shaped. To affect these various attributes you can increase or decrease the length of the propellers and the pitch of the propeller
Propellers normally come with a fixed pitch although sophisticated model do have a controllable variable pitch. The pitch is the shape and slant of the propeller. Longer propellers can achieve stronger lift at lower RPM than a shorter propeller, but it does suffers to take longer to speed up and slow down. When you need manoeuvrability then choose a shorter propeller.
But you cannot have too long a propeller otherwise it will be very hard to fly. In the future there may be propellers that change shape to achieve efficiency. Usually if more power is needed, you just add more propellers like hexacopters and octocopters.
Shorter propellers allow the quadcopter to change speed quickly and do tend to produce better maneuveribilities but at the expense of using more power. This will cause excess strain on the motors, which may burn them out.
An efficient quadcopter will have properly sized, low RPM motors with very large props. If you need to race your drone, then you need a more aggressive pitch, but if you need a utility model and since quadrotors need to hover, you want a lower pitch.
Battery – Drones need powering so a battery is needed. And no ordinary battery at that because you need a battery that is able to supply that large amount of power at a flick of a switch and also one that is quick to recharge.
Most drone battery is made from LiPo (Lithium Polymer) combination and they use a C rating, which stands for its capacity to discharge. A LiPo battery have has something like “20C” and if have a 25C 4000mAh LiPo battery, it means that you can get a maximum of 25C * 4 = 100A (A standing for Amps).
The power of the battery is usually dictated by the energy draw required from the electronic speed controller (ESC). For example if you motor’s maximum draw is 20A, at the very least you’ll want a 30A ESC to be safe. Now multiply that by the number of propellers you have (4 in this case) and you’ll get the maximum draw for your entire quad – 4 * 20A = which is 80A. Your 4000mAh 25C LiPo will be able to handle it.
A drone battery should not be fully discharged, and it needs to have a minimum voltage requirement, which if exceeded can cause damage to the battery. A normal case is 3.0 volts, but varies from battery to battery. A hold of 80 – 85% is preferable and once this mark is passed, battery power will drop precipitously. You should need to be landed once you hit this mark
A drone battery charger is specially designed for the particular and you will need to use only that for the charging. Charging a LiPo battery past 100% could actually. You’ll also notice that most quadcopters come with a battery charger specially designed for the battery.
It’s important to use the one they supply you with. It controls how much current is sent to the battery. Charging a LiPo battery past 100% could cause overheating and might trigger a fire near its surrounding so similarly, you are not supposed to charge your phone when you are on a plane
Electronic Speed Control (ESC) Now, you now have a frame, a motor, multiple propellers and also a battery, what else do you need to make it fly? And flying is not a joke. Yes, you will need a speed controller (ESC) so that you can manoeuvre it and a speed controller is a marvel of an electronics gadget! ESC’s also come with a microchip!
There is one ESC for each of the motor as motors can be driven at different speeds. What an ESC does is that it supplies the proper modulated current to the motors, which will in turn perform differently. Nowadays, ESC’s come with a SimonK firmware (also BLHeli), which handles the precise timing of multiple rotors. SimonK is suited to utility type and BLHeli or BLHeli_S is suited for racing and fast manoeuvrability.
Also, new ESCs come with a battery eliminator circuit (or BAC), which allows the flight control and transceiver components to connect to the ESC directly simultaneously draw power
Flight Control Board-Now another component is the Flight Controller Board which is basically the little computer which controls the movement of the drone. The FCB is also a radio signal receiver and a transmitter. This is necessary because it needs to receive commands (where it is not autonomous) as to what to do and also sends out radio signals as to inform what it is doing.
Now, flight controllers also have sensors like accelerometers, gyroscope, compass, barometer, cameras, GPS and inertia measurement units connected to it so that it can sense what’s going on with the drone. If you build your quadcopter then you will need to choose your FCB to suit your purpose especially where customization is required.
Where FCB’s are concerned, we normally talk about how many channels it work with. The minimum is four and it can go up to nine. The more channels mean that it is capable of controlling more sensors or actuators. There are a lot of very versatile receivers which work quite well with drone flight controllers.
Two channels is needed for a single action like move left or right. If you need to upgrade later on it is best to choose an FCB with more channels but do bear in mind that more channels mean more weight and sucks up more power!