The Complete Guide to RC Electronics

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Currently looking for a summer internship in engineering! Interested in everything from djing to...

Hello, my friends.

I have often found hobby RC electronics to be of interest in my projects due to their apparent simplicity and ease of use. However, it took me a while to figure out how to put together all the different components, figure out where to get all of the stuff, and read all of the (rather peculiar) ratings when I was trying to build something. Therefore, I hope that this guide will speed things up for you and lead to successful projects.

Quick reference:
1 - Where to obtain parts
2 - Transmitter
3 - Reciever
4 - Servos
5 - Motor controllers
6 - Motors, Propellers and Gears
7 - Batteries

Step 1: Where to Procure Components

After much research, i have found the following to be reliable, have a reasonable price, and have good selection:
 - Hobbyking: A Chinese-based distributor with a huge selection of motors, controllers, and everything else. mostly flying things. Shipping takes forever.
 - Horizon Hobby: Based in the USA, also have a large selection of items, but mostly ground-based vehicles.

There are other, cheaper websites, (like GoodLuckBuy) however I have heard that the reliability and customer service of these is often compromised.

Step 2: Transmitter

Also often abbreviated as Tx, this is the thing that actually takes your commands and sends your receiver the commands for the servos and the motors.

There are many Transmitters available on the market nowadays, and the low-cost ones start around $30. However, remotes for RC airplane or helicopter pilots, with programmable features, model memory, and computer simulators can start around $150 and go to nearly $3000.

All RC Remotes have a certain frequency that they operate on. Older, analog remotes operate on lower frequencies, which were determined by a crystal. Modern, digital, remotes usually operate in the Gigahertz Range, often at 2.4GHZ.

RC airplane and helicopter remotes have control sticks, which are mostly self explanatory. Usually, one of the two control sticks on an airplane remote is the throttle control stick, and is not spring loaded in the vertical direction, which means it will not spring back when you let go. Remotes are usually available with this stick on either the left or the right side, and are sold as mode 1 or mode 2. RC car remotes have a trigger and a knob to control different things.

Most RC remotes have something next to the Control sticks called the trim. this basically slightly alters the position of your control sticks, and is useful for finely altering the position of the servos, or the starting point of a motor controller. Transmitters also often have reversing, which reverses the output signal of the control sticks. this is usually controlled by a series of switches at the bottom of the transmitter.

The number of channels a remote has shows how many things it can control. For example a three channel remote could control three things, such as three servos, three motors, or a combination of any of those. Motor controllers and servos receive the same type of signal.

Expo, Telemetry, Limited travel and Model memory are all things seen on better, more expensive transmitters, but are not necessary for the average project. Expo stands for exponential rates, so that linear movement of your control sticks will result in an exponential output signal curve. Telemetry transmits information from the vehicle (such as battery voltage, altitude, motor temperature, etc.) back to the transmitter and displays these on the transmitter. Limited travel means that by moving your control sticks to their maximum will only send out a 30% signal, or whatever you set it to. both of these features are beneficial to sensitive mechanisms and airplanes, so that one can maintain better control over them. Model memory simply allows you to store your trim settings in the transmitter, so that you can recall them for later use, or eliminate the need of having to readjust with every time if you have multiple devices. RC car remotes are often equipped with dual rates, expo, memory, and even telemetry.

Most Transmitters need to bind to your Receiver to ensure proper communications. How to do this depends on your Transmitter/receiver.

Many transmitters need 12v to operate, usually supplied by 8AA batteries. this is 8 batteries too many for me, so i got a small, 0.8Ah battery and hooked it up to my remote, so that i only have one battery to worry about, instead of 8 small ones.

A cheap, beginner-level Transmitter that i can recommend from personal experience is the HobbyKing 6S.

Step 3: The Reciever

The receiver, abbreviated as Rx, receives the signals of the transmitter, and sends them out to the individual channels through PPM, or Pulse Position Modulation commands.

The Receiver must operate on the same frequency as the transmitter, and the two will usually be sold together.  Replacement or extra receivers are commonly available, so that they do not need to be switched out if one has more than one devices requiring a receiver.

The receiver usually receives power from a motor controller, simply by plugging it into one of the signal ports. Servos receive power from the receiver.

The Polarity of the plugs is usually found out by trial and error, in one way it will work, and the other way it probably will show a flashing light or something similar. Make sure to never connect one wire one way and another with opposite polarity to that wire, because depending on what those two things are, they will most likely be damaged, because one is going to be reverse polarity.

Some servo or motor controller connectors have a small plastic tab on them, and can therefore only be used with RC car receivers that can easily be removed with wire cutters.

Be careful with the antennae of digital receivers, because they are rather difficult to reattach.

Step 4: Servos

Servos are geared motors connected to potentiometers that are usually capable of 180 degree rotation, but with RC control usually only rotate 90 degrees. They take the receiver's commands in PPM form and rotate to a set position. they will attempt to hold this position if f force is applied. Although normal servos have a limited range, there are extended range servos, which rotate 360 degrees or more, and even continuous rotation servos, which have no control electronics and function as a normal gear motor.

They all have the standard three pin connectors, with ground (black), +4.8 to 7.4v (red), and signal (white).

Servo s are usually classified by weight, and also have a torque rating. This rating is usually given in Kg.
What this means is that the servo has x Kg force one centimeter out from the axis of rotation. So a 50Kg servo could supply 50Kg of force 1cm out from the axis (or 25kg 2cm out from the axis, etc...).

Some Large servos need a separate power supply because of their current demands, and would most likely just burn through your speed controller's power supply or your receiver's PCB traces. Use an UBEC with these. this is basically just a step down voltage regulator that provides a constant voltage to your servos.

Step 5: Motor Controllers

Motor controllers, also known as ESC's (Electronic Speed Controller) are very simple to use. Their purpose is to take a low power input signal in the form of ppm, and the battery voltage, and convert it into something useful for the motor. They also have a voltage output through the signal wire, and are often used to power the receiver.

There are essentially two types of motor controllers: brushless and brushed controllers. Brushed motor controllers only work with brushed motors, and send them a PWM, a Pulse Width Modulated (not PPM, Pulse Position Modulated) power input. These are simple and cheap, and can also be used to control lights and anything else that requires DC power. Brushless motor controllers are quite different. They switch power between the three combinations of two of the three poles of a brushless motor, and modulate the speed of this according to the PPM signal.

The difference between Car ESC's and Airplane ESC's is that car ESC's usually come with a power switch, heat sink and a reversing ability, while airplane ESC's have no reversing capability (Switch any two of the motor wires to reverse spin of the motor), no power switch and usually only a minimal heat sink.

ESC's are also programmable, usually through a programming card or through the reciever and transmitter. This will vary depending on the ESC, but usually they have programmable braking, starting, and battery voltage cutoff settings.

Step 6: Motors, Propellers and Gears

Motors come in two variants: Brushed motors, which have small brushes that switch the power through the coils, and brushless motors, which need an external controller to do the switching for them.

Brushless motors are usually more efficient, can handle higher speeds and torques, can handle huge amounts of power, and are longer lasting because they do not have brushes to wear out. they usually come in out-runner or in-runner styles. Outrunners have the permanent magnets on the outside, and their housing spins with the axle. Inrunners have the permanent magnets on the inside and have a non-rotating housing. Outrunners have more torque, but less speed, and are usually used with larger propellers. Inrunners have less torque, but can reach very high speed, and are therefore used in geared applications, such as RC cars, or with small propellers.

Motors in the RC world often have an interesting rating called Kv. Although one would expect this to mean Kilovolts, it actually means rotations per minute per volt. A 300Kv motor would, in theory, rotate at 900rpm at 3 volts. the lower the Kv rating, the more torque but the less speed a motor has, and the higher, the more speed but less torque a motor would have.


When looking for a suitable propeller, the prospective buyer may be confronted with such things as "1247" or "12x4.7". These define the propeller's size and pitch. in this instance, one would be looking at a 12 inch diameter, 4.7 inch pitch propeller. Pitch is defined as the distance a propeller would move in the air under ideal conditions in one full rotation. Propellers are also often classified into "slow fly" and normal propellers. Slow fly propellers are usually for geared applications or low speed applications, and have a curved leading edge for more efficiency. Normal Propellers have a straight leading edge for better efficiency, and are usually used with faster motors.

Gears in the RC world are usually only sold as a replacement for RC car gearboxes. they are never sold by diameter, but only by the pitch (spacing of the teeth) and the number of the teeth. A Spur gear is usually a large gear, that is turned by the pinion, a smaller gear directly attached to the motor. 

Step 7: Batteries and Chargers

Batteries come in many different Shapes and sizes, chemistries, and ratings.

The two most common chemistries for RC applications are NiMH or NiCd and Lithium polymer batteries.

NiMH (Nickel metal hydride) and NiCd  (Nickel-Cadmium) batteries are heavy, weak and outdated. the only benefit is that they may be marginally cheaper, and less sensitive to shock, vibration, overcharging, and deep discharge.

Lithium Polymer Batteries are lighter, smaller, can deliver huge currents, and have a very large capacity for their size. A 5000mAh Lipo battery is about as big and heavy as 2500mah worth of NiMH batteries. however, if pierced, discharged too far, or charged too far, they will "puff", or expand. This means that the battery is close to exploding. do not use this battery anymore, and dispose of it safely. If you keep going, it will most likely erupt in a large ball of flame and launch chemicals and burning things everywhere. Never short these batteries, they will most likely explode.

Charging: get yourself a good charger, I can recommend the Turnigy Accucell-6. Most chargers do not come with a built in power supply, so make sure you have an adequate power supply for your charger. Follow all the charging instructions that come with the charger, and place your battery in a fireproof container or bag. Never leave it unattended while charging.

Batteries have a number of different ratings:

mAh or Ah:  Stand for milliamp hour or Amp hour. this is the capacity of the battery. 1Ah=1000mAh, which means a battery can supply one amp for one hour (or 1000milliamps for an hour)
S and P:       Stand for number of Series cells and number of parallel cells. the number of cells in series determines voltage, parallel determines capacity.
C ratings:     This is how much current the battery can give you. Multiply the battery's capacity in amp hours by this rating to get the current in amps.  There are usually two specified. the lower one is the continuous rating, and the higher one is the pulse discharge rating.

I usually use one standardized connector for all of my batteries, so that I can use any battery with any device, and can interchange them easily. It doesn't matter what you use, I use the XT60 connectors, just make sure that you have one type of connector for all of your batteries.

Get some silicone wire for your power connections, because it is a flexible, multi-stranded wire that will in general make your life many times easier.

Step 8: Final Comments

Thanks for taking the time to look at this guide. I hope you enjoyed it and that i could be of some help. I am by no means an expert in this area, and would love to get some tips on how to improve this guide, things to add, questions or comments. 

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    118 Discussions

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    Borg101

    6 years ago on Step 8

    For a complete RC noob, like myself - This guide was very helpfull.

    1 reply
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    DuaneN5

    10 days ago on Step 8

    I would like to thank you as a newcomer to the hobby I found your article to be very informative .
    I am a retired mechanic and as such I was thinking of things I might have mentioned but then I thought about where would a person draw the line as to what information you would share. After thinking about that I think it was almost perfect.It is not like you were writing a manual but simply sharing some of the basics(although if you were to write a manual I think you would do a great job) I was thinking I would warn of loose connections or changing wire gauge could cause resistance & or heat but you gave just the amount of info as you intended without specializing on a particular perspective.
    Thank you for the hard work & keep it up.

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    ijeee

    Question 25 days ago

    Hey bro? can i ask you a question? I have a esc here bought from lazada a 20A esc with brake the thing is after testing it on channel 1 and channel 2 the motor works fine and the esc but aftwe changing it to. channel 3 as soon as i throtle the tx the motor starts spinning and when i stop throttlingmotor wont stop so i remove the source and when trying again on channel 1 the esc malfunction constantly flicking red light do you know what caused this problem?

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    Fatfreddyscat70

    Question 5 months ago on Introduction

    What 2 sites for people that want to purchase in the USA.

    I’m dealing with planes. Ele planes

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    CHEFBOYAUBOY

    Question 6 months ago on Introduction

    I am having problems with the hook up of my MiniBipe with a FlySky 10 channel 2.4 GHZ transmitter and receiver. It is bound, the brushless motor works fine, but when I plug in the two servos for the rudder and elevator they make a noise and rotate in one direction only and do not respond to the transmitter

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    raghu4414

    1 year ago

    Hi,

    Guys I am not into electronics, and I have bought a RC car running with batteries from hobby king,, and the problem I am facing is without going for the on bottom which is below the car, and plug in the battery with car ,,the wheels are moving,, and a kind of spark comes as soon as the battery connector is joined to car,, and all this is happening with the car in off condition..

    Please help.

    1 reply
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    biolethalraghu4414

    Reply 1 year ago

    Sounds like your motor controller might be burnt out - try replacing it with a different one. Make sure you get the right one (brushed vs. brushless motor controller).

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    tjt1957

    1 year ago

    Very concise simple guide, however I'm looking for a more detailed guide in order to make custom units, mostly amphibious boats, etc..Like how to water proof in case of tipping or a shaft, how to run two different motors at different speeds off one Tx, etc...

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    tpace3

    2 years ago

    I'm trying to add a motor, battery esc, and receiver (Not using steering for now) onto an existing build.

    Do you know if there are any cheap kits I can buy and drop into it? I'm looking around $50 - $70

    A very high torque motor, rechargeable battery is the only real important parts.

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    ThomasY19

    2 years ago

    I am in the process of wiring three Turgery motors three electronic speed controles to a vosper torpedo boat , some where i found a link on doing this with two motors is to cut the white wire from the second motor so your receiver does not conflict and uses only the one motor to start and the other will start at the same time i tried this on my vosper and i can only get the center motor working tho it only runs for a few seconds could this be the speed controler over heating as they are water cooled so i am just sorting these problems out the way i have wired the motors in three lives three neutrals into one of each from the battery 30 amp fuse on the live each speed controler is 30 amp rated the motors are 25 amp rated these are inrunners (motors) , regarding the white wires is it possible that to get all three motors running cutting the outer two white wires from the reciver was wrong is it possible either the red or black is the wires to cut ? i should be able to sort this out as i am an electrical enineer working on large electric motors and small single phase and three phase units , the only thing that i can think is that each motor is going to need its own power sorce ?right now three power leads from one battery ,three receiver leads from speed controlers to receiver, can you point me why i cant get the two outter motors to run with the center motor , tom yarwood

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    banerjeesaby

    2 years ago

    My first read up on RC Components and it all made sense. Thanks for keeping it simple.

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    JeffR110

    2 years ago

    ok guys, stupid question, I want to install a two step on my gas rc car, can this be done?

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    jemats02

    2 years ago

    need help with my electronics.. I have a 30A esc, flysky 6channel transmitter and reciever, and a 3s 11.1 v 30c batt. I successfully bound the reciever and controller, but the motor won't turn, just making a continous beep, heeellllppppp please!!

    1 reply
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    biolethaljemats02

    Reply 2 years ago

    Hmm, it is difficult to troubleshoot from afar! Check that the transmitter ranges/trim is set to the middle, or try moving the trim up or down - sometimes if you have the stick on your transmitter all the way down, the transmitter transmits a low value but not 0 - some ESCs won't initialize until they get a signal of 0, to prevent the motor from turning unexpectedly. Other than that, make sure you have your esc plugged in to the correct channel.

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    Neonherz

    2 years ago

    Very nice guide! Any reccommodations on a budget Friendly, brushed (ha learned something!) ESC? Needed for 3 DC Motors - thank you!

    1 reply
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    biolethalNeonherz

    Reply 2 years ago

    What ESC to get mostly depends on how big your motors are and what battery you are running them off of - Make sure to get a motor controller with the Current rating you need and that is compatible with the S number of your battery.

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    jemats02

    2 years ago

    all my servos are working by the way, just the motor. the month is a 2200kv A2212/6T

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    Insha-789

    2 years ago

    Want to buy arduino for rc car and RX and TX set, please suggest some cheap and good website

    is it normal for me to buy 2 (8 gram)servos,1 motor 720 kv,a esc,and a 2200 mah lipo battery for 120$?if itsn't i just got fooled(i live in indonesia so it should include a 10%tax)