Connectors and plugs for quadcopter newbies
Articles
Turnigy 460mAH battery with male JST BEC / RCY connector, and female JST BEC / RCY to female XT60 adapter cable
The first time I looked at a DIY quadcopter, I was fascinated… but also quite intimidated. Look at all those exposed wires and connectors! I quickly realized that there aren’t actually very many parts to a quadcopter. It’s a pretty simple thing to build, actually, and doing a quick Google search for “how to build a quadcopter” yields numerous step-by-step tutorials on how to build one for as little as $140. You should go to those articles if you are interested in learning how to build them. The builds themselves are relatively straightforward, if you can do a bit of soldering, but for me, it was the connectors that were confusing, and took time to sort out.
There are dozens, of not hundreds, of connector types, and if you don’t know what someone is called, it is really hard to find it online. I did many searches for things like “little red connector with 2 wires,” with varying amounts of success. Finally, after reading for hours, I chose a few connectors I like, and standardized around them. Here is my list of connectors, which comprise the vast majority of power and control connections I have been using in my builds:
- XT60 2-pin power connector. Used for high-current battery connections. I like this connector so much that it has its own post.
- JST BEC / RCY 2-pin power connector. Tiny and red. If you need low-current connections, these are fine.
- 3.5mm bullet connector. Single connections. Typically, 3 are used to connect a motor to an electronic speed control (ESC).
- JR universal servo plug (same as Hitec “S” connector)
1. The XT60 connector
XT60 female connector, soldered onto a LiPo battery
Again, this connector has its own post. If you have an existing battery or power connector, don’t be afraid to cut it off and solder a new connector on. Remember not to short batteries out when you’re working on them. You can get a nasty shock and, if you’re unlucky, start a fire.
2. The JST (BEC / RCY) 2-pin connector
JST BEC / RCY male and female connectors on 22 AWG wire
This is a great little connector for low-current usage. Some people use them for as much as 20A, but that makes me nervous. This guide suggests that 22 AWG wire (~0.65mm) shouldn’t be used for more than 7A.
I like to buy these things with pigtails already soldered on (male, female) . The female ones from HobbyKing have been out of stock forever, so I just ordered the connectors, separately (male, female). They require soldering and/or a crimp tool to connect to wires.
These connectors are a bit strange, since the one sold as “male” is actually female, and the one sold as “female” is actually male. I decided to use the one sold as “male” on the power side, and the one sold as “female” on the receiving side. Don’t judge me.
I have a male connector on the auxiliary power wires provided on my DJI Phantom. I use it to power my FPV setup. I’m also using as a power connector on a Rotorpixel brushless gimbal.
Turnigy 460mAH battery with male JST connector, and female JST to female XT60 adapter cable
Speaking of gimbals, sometimes I want to test the gimbal without powering up the quad, so I hacked the Deans connector (boo!) off of a small 3S battery and put a JST BEC / RCY connector on it. This battery is rated to 40C at 460mA (18.4A), so I am just careful not to connect it to power-hungry circuits.
I have to charge this little battery, and instead of making a banana plug to female JST BEC / RCY charging cable, I made a female JST BEC / RCY to female XT60 adapter cable. To charge this battery up, I plug the adapter cable in, and it now can be charged just like one of my normal batteries.
Oh, yeah. Sometimes, you want to split power in parallel (so both leads get the same voltage). You can choose to solder your own (YouTube has great tutorials), or buy them. I couldn’t find these cheaply, but Horizon Hobby has them for $3.99, each (update, May 24, 2013: The Horizon Hobby y-cable I bought had polarity reversed, and I had to re-wire it. I would not purchase one from them. Instead, buy the $5.99 version from ReadyMadeRC).
3. The 3.5mm bullet connector
3.5mm bullet connector (source: HobbyKing)
3.5mm bullet connectors are often used to connect motors to ESCs. I decided to standardize around the PolyMax 3.5mm Gold Bullet Connector, sold by HobbyKing (a backup is this 3.5mm bullet connector, if that one is backordered), which costs $1.81 for 10 pairs. If you decide not to solder your motor wires directly to your ESC, you will use 3 pairs per motor, or 12 pairs per quadcopter. You will use a bunch of these, if you have multiple copters. I bought a crapload in a single order, since shipping from Asia is expensive. I tend to heat shrink them instead of using the plastic insulators (4.0-4.5mm heat shrink works well). The internets say that you can use 8 AWG wire in these, but I use thinner wire. I’m only working with 20-40A per connector, so 12-16 AWG is fine.
4. The JR universal servo plug
JR servo plug being used to talk to a motor on a Rotorpixel brushless gimbal
There are at least 5 different servo connector types. The DJI Phantom uses the universal JR servo plug, and so I decided to standardize around it. The Futaba “J” type connector is exactly the same, except that it has an orientation tab. If you cut the tab off with an XACTO knife, they can be used interchangeably with JR plugs.
Again, I prefer to buy these cables ready made. 10-45cm leads (and a bunch of extensions) are available on HobbyKing, using 32AWG wire. They are inexpensive (e.g., 10 x 20cm servo leads cost $2.75 plus shipping). Note that to find these leads on HobbyKing, you have to search for “jr servo lead”. I did a lot of searching with “cable” and “wire,” and couldn’t find anything on the site.
Other things to buy
When you’re ready for an order, buy more connectors than you think you’ll need and load up on wire (I bought a bunch of wire from 10AWG to 22 AWG) and heat shrink of all sizes. The worse thing is to halt a build for a day or more because you’re missing 1 little part!
Also, considering getting a soldering aid for connectors. There is Mr JIG, an aluminum soldering aid that uses a clamp ($8.23, HobbyKing USA Warehouse) and Mr Grippy , a carbon-fiber model that uses a spring ($8.11, HobbyKing USA Warehouse). I bought Mr Grippy because I like springs, and it has vertical posts for clamping wires in place.
DJI Phantom with Rotorpixel Gimbal Lite and GoPro HERO3 camera… and a bunch of connectors
I hope this little article has helped you, especially if you are new to the hobby. There is a ton of incredible information out there about the hobby from experts, but it can be time consuming to mine forums for the data. Also, I find that I’m already starting to take some of this knowledge for granted, so it’s important to get as much of it out of my head as possible, while it’s all fresh. 🙂