Connectors are electromechanical devices which link two different circuits together through conductive contacts. There are a broad variety of connector types which serve different purposes in an electric circuit. Choosing the correct one is essential.
For any form of quick prototyping and testing, DuPont connectors are the way to go for communications. They are versatile and can be assembled/disassembled relatively quickly. For components which draw large amounts of power, a combination of alligator clips, banana connectors, and 12AWG wire (or whichever gauge is proficent) should suffice, provided that the power is DC and <50V, and proper safety precautions are being taken to prevent shorts (i.e. power supply is current-limiting or has a fuse, wiring is secured and not prone to being "yanked apart," exposed wire is taped or heatshrinked, no conductive surfaces have a chance at touching any part of a live circuit, etc).
For final builds/flight hardware, these connectors should be used for supplying large (>2A) amounts of current/power from a battery/power source, or supplying to power-intensive hardware:
Final builds implementing sensor communication or supplying smaller amounts of power (<2A) should use these connectors:
In rocketry, there are only a few types of connectors which we will regularly use. Minimizing the number of different connectors in a project will greatly reduce the effort necessary to source and properly assemble connectors. Therefore, teams should put effort in standardizing connector use across different projects and components.
"Header pins," also referred to as DuPont connectors, are some of the most commonly used pins for beginner projects. A male DuPont pin can be easily inserted into a breadboard, and a female DuPont connector can be inserted into the GPIO pins on the Raspberry Pi and other microcontrollers. Many other beginner electronics components come with header pins presoldered onto them, allowing new users to "plug and play."
Header pin rows generally have a spacing (more formally, a pitch) of 2.54mm, or 0.1 inches apart when measured from the pin's center. Some electronics may use a narrower pitch due to their size, such as XBee radios.
These pins are excellent for prototyping, but not ideal for final builds. The pins do not have any locking mechanism and are prone to coming loose when not making good contact. The quality of these connectors vary, making it very common to find connectors which simply "slide off" the header pin. Flight hardware should make use of more robust connectors, or at the very least secure the connections with tape or hot glue.
A VGA cable is an example of a common D-Subminiature connector. These connectors have varying numbers of pins and can be screwed together for a secure fit.
There are many variants of D-Sub connectors, with the most common being the DE-9 connector (more colloquially and incorrectly known as the DB-9 connector). DE-9 connectors contain 9 pins, and many variants of D-Sub connectors with varying housing sizes/pin spacing and pin count are available.
These connectors have the disadvantage of being very bulky. They may not fit nicely into flight hardware, but can be excellent for prototyping.
Japan Solderless Terminal Connectors, or JSTs, are small pcb-mountable connectors. They are very commonly used in many electronics, notably stepper motor connectors and small RC-batteries.
A very commonly used model of JST connector for stepper motors are the JST-PH-2.00mm series. Many LiPo batteries use the JST-RCY-2.50mm series connectors.
The JST-PA-2.00mm is a connector with a built-in lock mechanism, which helps reduce the likelihood of it breaking free under vibrational loads.
These connectors are an excellent choice for routing signals due to their compactness. They are fairly simple to connect/disconnect, which makes integration easier. These connectors have relatively low current limitations, so they may not be suitable for supplying power to larger components.
XT-60 connectors are commonly used in larger LiPo batteries. They are relatively robust and commonly used on drones and RC cars. They are rated for up to 30 Amps and 500V, making them ideal for use in a system battery/power supply.
This standard describes a circularly-shaped connector which is commonly used in many orbital launch vehicles and other military applications. These connectors are extremely robust and were designed specifically for flight hardware, but they are also extremely expensive to obtain.