Now that you have chosen all the main components for your UAV, you can start assembling. This guide will cover common mistakes when assembling a multi-rotor UAV, as well as some helpful tuning tips. This lesson will not cover items such as a camera/FPV system, long-range devices or other accessories (we’ll cover it in lesson 7).
Components you should have at this stage:
- Frame (purchased or handcrafted)
- Motors, ESC, propellers, battery, charger
- Power Distribution Board/Connection Harnesses
- Flight controller and communication device (radio control suggested)
To achieve the goals of this tutorial, your UAV powerplant will include the following components:
- Power distribution (board or wiring harnesses)
- Accumulator battery
- flight controller
Please note that there are no propellers in the list. Do not install propellers at this stage! The rotors will only be connected in lesson 6. Since this is your first drone, we recommend doing a “frameless” electrical connection before putting everything on the frame; in order to check all connections and eliminate the identified malfunctions.
Battery. Power distribution
The connection between the battery and the power distribution system should be relatively simple if they both have the same type of connector. If so, then proceed to the next step. If the connectors are different, then in no case do not cut the battery wires to separate the connector; this can cause a short circuit and a nasty electric shock! Instead, you can pick up an adapter and use it between the battery connector and the power distribution board connector. Another option may be to search for a mating connector to the battery connector, and buy it; then cut the existing connector from the power distributor and solder the purchased replacement, after making sure that there is no connection between the positive and negative contacts.
It is important to note that most multi-rotor UAVs do not have an on/off switch, so power is turned on and off by connecting and disconnecting the main battery from the power distributor connector, so their connectors must be securely fastened and the wires / solder points are well insulated with heat shrink tubing and / or tape.
Disconnect the battery from the power distributor before proceeding.
Motor. ESC. Power distribution
The Power Distribution Board (PDP) or wired distribution primarily serves to distribute power from the main battery to each ESC. The voltage is applied to the ESC “as is”, so there is no need to increase (increase) or decrease (decrease) the voltage. If your drone has four motors, then you must have four ESCs, and therefore your distribution board/wire distribution must eventually split the main battery into four connections. If your PDP has six connections, and you are building a quadcopter, then you simply do not need to connect the last two. If you are building a hexacopter, your HRP must distribute power from the main battery to six connections. ESC includes the following wires:
- One 3‑wire 0.1″ R/C cable, where the black pin is normally ground, the red pin provides 5V output (via BEC*), and yellow/white is the signal input.
- Three separate wires are used to connect to three wires on a brushless DC motor (usually supplied with female bullet connectors that are either already soldered or included).
- Two input connectors for connecting the battery to the PDB (some include soldered connectors with soldering, some are included, and sometimes not included at all).
*ESCs usually have a built-in battery elimination circuit (or BEC) that converts the main battery voltage to 5V to power the receiver and flight controller. 5V is usually supplied through the RC connector from the ESC (usually the center/red pin). You only need one BEC to power the flight controller.
If the power distribution board uses connectors that do not match the connectors on the ESC or battery, then you will need to either purchase adapters (adapters) or purchase new connectors and replace them with the ESC or PRP. The advantage remains with the power distribution board, the connectors of which coincide with the battery and ESC connectors. Most often, a lithium-polymer UAV battery can have a DEANS connector, XT60 or EC3.
If you want to power additional low current electronics (LED lighting system, pendant, etc.) but your power distribution board does not have spare connections, you can use a battery charging cable. The white charging connector usually has one ground pin and one pin for each cell (1S, 2S, 3S, etc.) used in a LiPo battery assembly. Although this connector is really only for battery charging, it can provide 3.7V output from each pin and can be used to power low current electronics such as a grid or LEDs.
- Remove the red lead from each 3‑pin ESC R/C connector except for one. It is recommended to do this in such a way that, if necessary, you can always connect them back. Wrap the end of each excluded wire with electrical tape or use heat shrink tubing for insulation so that later they cannot come into contact with other electronics. The only red wire left untouched will power the flight controller used in the assembly.
- Connect the two power wires of each ESC to the distribution board, making sure the red wire goes to positive (+) and the black wire to negative (-).
- If the power distribution board you are using has its own R/C connectors, then it is up to you to connect the R/C pins of each ESC to the R/C connectors on that board, or connect them directly to the flight controller.
- Connect each of the three motor connectors to the three speed controller (ESC) connectors. At the moment, the order of connecting these connectors is not important (if it affects the direction of rotation, it will be corrected as necessary later).
Please note that if you choose to remove or hide the wiring at this stage, you may later need to access some of the connections following the procedure in Lesson 6, specifically swap the connections between the ESC and the motor so that the motor rotates in the opposite direction. .
ESC. flight controller.
Now you can connect the R/C inputs of the ESCs to the flight controller. The flight controller you choose should have a diagram that shows which controller pins your multirotor assembly’s motors are connected to. Also in this diagram, the direction of rotation of each motor should be shown, but again, you do not need to consider the direction for now.
- See the connection diagram between the motors/ESC and the flight controller in the PC manual.
- Connect the R/C connectors of each ESC to the corresponding pins on the flight controller, make sure the ground wire (usually black) is connected to the ground pin on the flight controller, and the signal pin (white or yellow) is connected to the signal pin on the flight controller.
- Only one of the RC connectors will still have a red (power) contact.
Receiver. flight controller.
Let’s assume that in this lesson you have chosen radio control as your input device. If you want to use WiFi, Bluetooth, or other input method, please read the flight controller manual and find the serial input; this section will describe how/where to connect a serial input device to the flight controller. Most likely, you will need to find and connect the transmit (Tx), receive (Rx), voltage (5V) and GND pins from the wireless device to the transmitter, providing Rx from one to the Tx of the other, and vice versa.
Your RC transmitter must come with a matching RC receiver. The receiver must be bound to the transmitter so that you can remove the bind jumper from the receiver (if present). The kit may also include the AA Battery holder, which is designed to power the receiver, but we will not use it, since the BeC will feed both the receiver and the flight controller. To find out which RC receiver channels are connected to which contacts on the flight controller, you need to look at the user management of both the flight controller and the RC system.
The flight controller manual will list the locations of the following pins, which must be matched and connected to the receiver:
- Auxiliary (Aux) switches 1, 2, 3, etc.
Now you can make the following connections:
- Read the guide to the flight controller to see which input R/C the contact is associated with which of the above functions.
- Read the guide to the transmitter to find out which channel is associated with each of the functions.
- Some RC transmitters can be reprogrammed to change the functions of each contact. If you decide to change any entrance (joystick or switch), do this only after you know that you know which channel on the receiver corresponds to what function. Throttle, Pitch, Yaw, and Roll should always be associated with two sticks/joysticks, and not with switches or buttons.
- Connect the Throttle channel on the receiver to the Throttle input on the flight controller.
- Connect the Pitch channel on the receiver to the Pitch input on the flight controller.
- Connect the Yaw channel on the receiver to the Yaw input on the flight controller.
- Connect GND on the flight controller (usually the third row of contacts) to GND at the receiver (usually the third row of contacts).
- If an auxiliary entrance is used, connect AUX 1 on the receiver to the AUX 1 on the flight controller and so on.
You can use 3‑pin servo wires for each of the channels, but only one of the channels (maybe any) should have voltage and grounding; the rest only need a signal wire. All connections can be GND to GND, although only one is required. Once again, the receiver does not need a separate battery, since it will receive food from the flight controller, which receives food from the BEC from one of the ESC.
If you are building your own frame, you can assemble it at this stage. If you purchased a frame kit, follow the assembly instructions. Please note that you may need to disassemble certain areas to facilitate the connection or remove (hide) electrics. The goal is to guarantee that nothing is weakened, all wires are reliably fixed, and nothing can fall out of the frame or get confused.
Accommodation of the battery.
The battery used for power is often the most severe element on the UAV and can be from 1/4 to 1/2 of its total weight. Therefore, the place of its installation is very important. The ideal location for the main battery should be in the center of the aircraft so that all motors can handle approximately the same load. If the battery is located closer to the rear of the aircraft, the rear motors will need to provide more thrust than the motors in the front, and thus the maximum total thrust will be limited (when the rear motors are at full power, there will be no thrust on the motors in the front). Whereas the usual approach in a multi-rotor design is for the quad to be symmetrical about a central axis (or at least one axis), so the battery should be placed along that center line, rather than offset to one side or the other. .
Next, you will need to decide at what height to place the battery. There are several places where the battery can be installed:
- Under the frame (copter will be heavy underneath, more stable and less acrobatic).
- Directly under the motors (usually inside the frame); perhaps one of the best places.
- At the same height as the engines or carrying screws (for example, installed in the upper part of the frame).
- Above the propellers (UAV will be top heavy and more prone to flip).
For best performance, the battery should ideally be located in position 3 above. Position 4 creates an inverted pendulum effect, and if the UAV tilts beyond a certain angle, the drone will tend to flip. Position 1 will create a fairly stable platform that tends to stay level by nature, but is highly unsuitable for acrobatics. Therefore, most designers choose position 2 and place the battery either directly under the frame or inside it. This approach frees up space under the frame for the payload, such as the gimbal system, and space above for the flight controller and other electronics to be as accessible as possible.
There are many generally accepted ways to attach the battery to the frame, which include:
- Velcro belts
- Self-adhesive Velcro (one side is glued to the battery, and the other to the frame)
Velcro straps are most common on mid-size “standard” sized custom drones, while framing is most common on commercial drones, the frames of these drones are often injection-molded and leave space inside specifically for a particular battery. Velcro should ideally only be used if the battery is relatively light; instead of one short section in the center, it is recommended to glue one strip along the entire length of the battery. If you are using Velcro straps and find that the battery is prone to pop out due to lack of grip, it is recommended to add rubber strips where the battery contacts the straps. It is not recommended to use glue to attach the battery to the frame. If you are not using the UAV, remove the battery and store it in a LiPo safe bag or ceramic tank.
It is very likely that you have chosen a lithium polymer (LiPo) or other lithium battery. Most LiPo batteries over 3.7V have a separate cable with a multi-pin connector for charging, while the power cable can be identified by the presence of a two-pin connector with larger wires that can withstand a large discharge current. The charging connector usually has one pin for each battery cell, as well as a common ground pin.
Due to the dangers associated with LiPo batteries (hydrogen and electricity), it is common practice to completely remove the battery from the drone when not in use and place it in a “LiPo Safe” bag. The same bag is used when charging the battery (connect the battery to the charger, place the battery in the bag (leaving the charger out of the bag) and close it (usually it has a velcro flap).
Placement and installation of the flight controller
Ideally, the flight controller should be located in the center of the drone at the same height as the motors. If this is not possible, then the controller can be placed a little higher or lower. Do not mount the flight controller more towards the left or right side, and avoid mounting it forward or backward. If you purchased a frame for an UAV, these often have mounting holes for the flight controller, which are in the optimal location. The flight controller can be secured in any of the following basic ways:
- Screws/Nuts/Stands (basic)
- Double-sided adhesive tape (make sure it’s strong enough)
- Double-sided adhesive foam (to achieve a damping effect)
- Rubber damping bushings (for significant damping)
Some flight controllers either have, or may optionally have, a protective case. This case protects the circuit board from dust and a few drops of rain and can take the hit in the event of a crash. In some cases, rubber dampers/grommets are used to reduce vibration caused by unbalanced motors/propellers. The perfect assembly is Max. a rigid frame with a perfectly balanced power plant and a well-isolated flight controller from vibrations.
Placement and installation ESC
ESCs are connected between motors, distribution board/cable and flight controller. The standard length of the ESC wires and motors generally do not need to be lengthened during the assembly of the multirotor. ESCs must provide high current and, accordingly, can become very hot during operation. The ideal regulator location is directly below the main rotor blades on the reference beam; this approach will provide him with good cooling. The ESC can be attached to the pole with zip ties (one on each side of the ESC), tape, or just about any other method that won’t interfere with heat dissipation. ESCs should not be installed in a location that limits heat dissipation (such as in an enclosed metal box) and should be located away from sensitive electronics such as a flight controller or receiver.
RC receiver and antenna
The RC receiver itself can be placed almost anywhere on the drone. The exceptions are places located in close proximity to power wires (away from the battery and ESC). The receivers that come with RC systems usually don’t have any particular mounting method, so a good quality double-sided adhesive is the best option.
The antenna attached to the receiver is usually a flexible wire. This wire must be located in such a way that nothing interferes with signal reception. It can be fixed either along the reference beam (on the opposite side of the ESC) or along the landing leg. In Lesson 6, we’ll talk more about range testing, which must be done to find out the maximum distance at which a receiver can receive a signal from a transmitter. Range testing may require you to experiment with different receiver and antenna locations.
Positioning and Mounting the GPS Antenna
Unlike a wired receiver antenna, the GPS receiver antenna tends to be either a “Duck” antenna (hard plastic fixed pole, 90 degree or hinged) or rectangular and relatively flat. Some GPS devices have a built-in antenna (i.e. the antenna is part of the printed circuit board). In any case, the GPS antenna must be mounted on top of the UAV so that satellite signals are not blocked. Mounting a rectangular antenna is usually done with double-sided tape, while mounting a “duck” antenna usually involves drilling mounting holes. If the “Duck” antenna is connected directly to the flight controller, then no additional wiring is required.
At this point, you should have a fully assembled and connected UAV, minus the propellers. Lesson 6 includes setting up and testing the transmitter, flight controller software, pre-flight checkout, and first flight.