How to wire a quadcopter is often assumed to be common knowledge, but when I started to build my quadcopter a few months ago I knew virtually nothing about rc wiring or electricity and had to search around a lot to figure it out. This post is an effort to describe what I have learned and how I wire my quadcopters.
There are lots of good wiring diagrams on the net, but sometimes they can be confusing to read, so I took this picture to describe how I wire my quadcopters:
Continue reading to see my explanation of the above wiring layout…
* For simplicity, I have only shown two ESCs and motors in the picture above, but on my quad, all four of them would be connected.
- The ESCs are connected to the battery in parallel via a wiring harness.
- The other side of the ESCs are connected to the four motors.
- Each ESC’s BEC (battery elimination curcuit) is connected to the appropriate motor pins on the flight control board.
- Connections are made from the flight control board to the receiver for power, pitch, roll, throttle, yaw, etc.
- To monitor the charge level of my battery I connect a little monitor/alarm directly to the battery’s balanced charge connector
I connect my batteries to my wiring harness using an EC5 connectors. Some folks prefer using Deans and XT60 connectors, but I like the EC5s because they are big and easy to solder. To use them, I had to replace the existing battery connectors. When soldering on the new connectors, I was careful to only cut off and work with one battery wire at a time to avoid the two wires ever touching and getting a shock.
A wiring harness is used to connect the battery to the ESCs. There are lots of different wiring harness ideas for quadcopters. Some people use power distribution boards that allow ESCs and batteries to be plugged in directly. This seems like a very elegant solution, but the board has to be connected to your frame and might be unwieldy. Other folks build or buy custom harnesses. Here is a video on how to build a spider harness and here is another good video on building a custom quadcopter harness.
I built my wiring harness to connect to the 8 ESC wires on my quadcopter to the battery in parallel. I ended up using 18 AWG wire for my harness because it was readily available. Each of the motors in this setup pulls a maximum of 10 amps and I use 18 amp ESCs. Larger motors and bigger ESCs may require higher diameter wire. Perhaps, these should be a higher diameter, but I haven’t noticed any problems and the 4 wires fit well into the EC5 connectors I use in my harness.
I made my harness using:
- 8 – 18 AWG wires, 4 red and 4 black.
- A male EC5 connector (two large male bullet connectors and a plastic casing) on the battery side.
- 8 – 3.5mm bullet connectors on the ESC side.
- Heat shrink tubing to cover exposed wires and connectors.
ESC battery and motors wires usually don’t come with connectors. I solder 3.5mm male bullet connectors to the battery side of my ESCs and female 3.5mm bullet connectors to the motor side of my ESCs.
Red battery and harness wires must be connected to the red (+) ESC power wires. Black battery and harness wires must be connected to the black (-) ESC ground wires. Not doing so can destroy the ESC, cause a fire or shock.
The three wires on the motor side of the ESC can be connected in any order. Reversing any two of the three motor wires will cause the direction the propeller spins to reverse.
The ESC BEC has a standard 3 wire servo type connector that is used to power and communicate with the flight control board.
Motors often come with male 3.5mm bullet connectors already soldered on. If not, I solder them on and add heat shrink.
Control Board and Receiver Connections
ESC BECs have three wires, a signal (usually white or orange), a power(usually red), and a ground(usually black or brown). The power wire typically delivers 3 amps of power that can be used to power the flight controller. Most flight control board manufacturers suggest that only one BEC power wire is connected. This can be done by removing the power and ground wires from all but one BEC or removing just the power wire from three of the four BECs. The signal wire must be connected for all four ESC BECs to transmit motor speed commands to the ESC from the flight control board. Here is an excellent post on the OpenPilot forum that discusses all the options.
Custom receiver connectors usually come with the flight control board and provide power to the receiver from the board and have signal wire connector(s) for pitch, roll, throttle, yaw, camera control, etc. A Pulse Position Modulation (PPM) TX/RX may only need 3 wires for power, ground and signal. With PPM all the signals are sent over one wire. A Pulse Width Modulation (PWM) TX/RX uses separate wires for each signal.
American Wire Gauge (AWG) is a standardized wire gauge system based on the diameter of the wire. The diameter of the the wire chosen for rc models is important. Wider diameter wires can handle more current. Unfortunately, I have found that the high strand count, flexible silicon wire that is best for rc applications, is not always available in all AWG diameters. Also, many of the components I buy use different wire gauges. Ideally, I would try to use the appropriate wire diameter throughout my quadcopter based on the maximum amps traveling through the wires. Here is a post from rcgroups that has some suggestions on proper wire sizes.
Unless you plan on buying a bunch of pre-soldered harnesses, motors and ESCs, it is necessary to learn some basic soldering skills to build a diy quadcopter. I don’t have very good eyesight or dexterity, so, if I can do it, anyone can.
I use two types of connectors in all my quadcopters. EC5 connectors to connect my batteries and 3.5mm bullet connectors for everything else. The EC5 is large and can easily hold 4 positive and 4 negative wires coming from the ESCs.
Soldering connectors to wires requires:
- Soldering wire that includes flux. Flux helps the solder flow.
- A soldering iron.
I bought a big spool of solder from Radio Shack. Harbor Freight and WalMart are great places to buy a cheap soldering iron. I have a 30 watt soldering iron from Harbor Freight. It only cost a few bucks and works great.
It helps to:
- “Tin” the tip of the soldering iron (coat it with a little bit of solder).
- Have a good clamp or jig to hold the work.
- Have clean soldering surfaces.
To solder together wire and bullet connectors I follow these steps…
- Strip the wire back to the same as the depth of the bullet connector.
- Tin the wire, which means filling and coating the end of the wire with solder
- Heat the bullet connector.
- Partially fill the bullet connector with solder (too much and it will spill over the side).
- Place the wire into the connector partially filled with hot solder.
- Hold the wire straight until the solder hardens.
Once all of the soldering is done, I connect all the parts to my frame always making sure red is connected to red and black is connected to black to avoid shorting something out.
That is how I do my wiring. It may not be perfect, but hopefully it helps someone. Of course, just because I did it this way doesn’t mean it is necessarily the right way or the only way, but it works for me. Remember that these are not toys (well, they kinda are) and dealing with electricity can be dangerous.