DIY Drone: Lesson 5. Assembly.

Content

Introduction

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:

1. Frame (pur­chased or hand­craft­ed)
2. Motors, ESC, pro­pellers, bat­tery, charg­er
3. Pow­er Dis­tri­b­u­tion Board/Connection Har­ness­es
4. Flight con­troller and com­mu­ni­ca­tion device (radio con­trol sug­gest­ed)

Power point

To achieve the goals of this tuto­r­i­al, your UAV pow­er­plant will include the fol­low­ing com­po­nents:

• Motors
• ESC
• 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.

1. 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.
2. 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 (-).
3. 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.
4. 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.

1. See the con­nec­tion dia­gram between the motors/ESC and the flight con­troller in the PC man­u­al.
2. 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.
3. Only one of the RC con­nec­tors will still have a red (pow­er) con­tact.

Connection

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:

• Throt­tle
• Pitch
• Yaw
• Roll
• Aux­il­iary (Aux) switch­es 1, 2, 3, etc.

Now you can make the fol­low­ing con­nec­tions:

1. Read the guide to the flight con­troller to see which input R/C the con­tact is asso­ci­at­ed with which of the above func­tions.
2. Read the guide to the trans­mit­ter to find out which chan­nel is asso­ci­at­ed with each of the func­tions.
3. 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.
4. Con­nect the Throt­tle chan­nel on the receiv­er to the Throt­tle input on the flight con­troller.
5. Con­nect the Pitch chan­nel on the receiv­er to the Pitch input on the flight con­troller.
6. Con­nect the Yaw chan­nel on the receiv­er to the Yaw input on the flight con­troller.
7. Con­nect GND on the flight con­troller (usu­al­ly the third row of con­tacts) to GND at the receiv­er (usu­al­ly the third row of con­tacts).
8. 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.

Frame assembly

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.

Mounting

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:

1. Under the frame (copter will be heavy under­neath, more sta­ble and less acro­bat­ic).
2. Direct­ly under the motors (usu­al­ly inside the frame); per­haps one of the best places.
3. At the same height as the engines or car­ry­ing screws (for exam­ple, installed in the upper part of the frame).
4. 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.

Battery installation

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)
• framed

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.

Charging batteries

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.