Connectors are found in almost every single electronic item. By definition, it is a device used to join electrical conductors to create a circuit. A connector is usually used non-permanently where there are plans to disconnect it in the future.
Almost everyone uses at least one electrical item every day, therefore it is good to know the different types of connectors available for your product for future replacement or tinkering. If you’re into tinkering with IoT products such as Raspberry Pis or Arduinos, it will be even more desirable to have this knowledge. We will not go into details about the nerdy specifications of each connector in this article, but we’ll introduce you to most of the basic common connectors and some articles to read more about them if you are interested.
Note: This article will be focused more on connectors used for IoT projects.
In this guide, we will be going through:
- Basic Jargons
- Various connectors and their categories
- Explanation of each connector
- Which connectors to choose for your application
- Recommended sites for further reading.
Let’s get started.
Basic Connectors Jargons
Here are some of the commonly used jargons that are used to describe connectors. It will be good to know them as we will be using these jargons to explain the connectors as well.
Female (left) and Male (right)
The gender refers to the part of the connector where its plugs in or are plugged into. Similar to the gender we’re familiar with, it is typically male or female. The male refers to the connector that plugs and the female refers to the connectors that are plugged into. However, there are instances where a connector would appear to be female but referred to as “male”. In the explanations section later, we’ll point it out and explain why.
Ref: Connector Supplier
Contacts refer to the metal parts of connectors that come into contact with each other to form a connection. Contacts may become soiled (stained) or oxidized (rust) that will make them unable to function anymore. The springiness required to hold the contact may also fade with time causing malfunction as well.
Ref: AC Works
Electric Plug connectors are divided into polarity-sensitive and polarity-insensitive. Polarity-sensitive connectors are designed to be plugged in a specific orientation while polarity-insensitive connectors can be plugged and unplugged in any direction. Electrical plug connectors come in three main forms: Two identical plug blades, Two non-identical plug blades, and Three plug blades. The Two non-identical plug blades and three plug blades variations can only be plugged in one orientation, meaning they are polarized. The Two identical plug blades variation can be plugged in two different orientation, meaning they are non-polarized. Plugs are polarized for added safety by ensuring the hot wired-pin will always be plugged in the hot-wired side of the outlet and vice-versa for the neutral side and pin.
Mating cycles refers to how many times a connector can be connected and disconnected until it wears out. Connectors have finite lives. The mating cycles can usually be found in datasheets. The mating cycles vary for different connectors.
Most connectors consist of an array of contacts in a repeated pattern. The pitch refers to the distance of the centre of one contact to the centre of another. This is important to know as many connectors has similar contacts but are different. Knowing the pitch will ensure you are purchasing the right one.
“Mount” can refer to several things for this case. How the connector is mounted in use: free-hanging mount, board mount, panel mount, etc. What the angle of the connector is relative to the attachment: straight or right-angle. How it is mechanically attached: surface mount, through-hole, solder tab. More examples will be given in the following sections.
Strain-relief refers to the slight flexible black fitting slotted on the tip of the connector. This is to provide strain relief to any forces acting on the fragile electrical connections. There will be more examples of this in the following sections.
|Table of Connectors|
|USB Connectors||USB-AUSB-BUSB-MiniUSB-MicroUSB 3.0 Micro BUSB-CReversible USB|
|Audio Connectors||Phone connector (audio)RCA connectorOther Variations|
|Power Connectors||IEC ConnectorBarrel connectorMolex ConnectorJST Connector|
|SMA Antenna connectors||SMA ConnectorRP-SMA Connector|
|Pin Header Connectors||Standard 2.54mm Single/Double Row ConnectorOther Variations|
|Plug and Play||GroveQwiicSTEMMA|
USB is the most connector to connect a peripheral to a host. In the USB standard, there are different types of USB, but they do share some common characteristics.
- Polarity: A USB connector is normally inserted in only one orientation. There are newer variations of USB connectors that are reversible.
- Shielding: USB connectors are shielded. A metal shell (not part of the electrical circuit) is provided to keep the signal intact in electrically noisy environments.
- Robust Power Connection: USB has power pins and data lines. Power pins are connected before the data lines to avoid the device being powered over the data lines.
- Four contacts: All USB variations have at least 4 contacts: power, ground and two data lines (D+ and D-). They can transmit up to 500mA at 5V. Some variations have even more contacts, which will be elaborated down below.
- Molded Strain-Relief: All USB cables have plastic molding at the connector to prevent strain and provide protection.
Here are some USB products you may check out:
- USB Type-C Male to Female Extension Cable with Switch
- Micro USB to USB OTG Cable
- USB 3.1 Type C to A Cable 1 Meter – 3.1A
USB is used in many different peripherals and devices. Keyboard, mice, printers and most computer peripherals are using USB for connection to the computer. Portable Drives also uses USB for connection. Smartphones also use USB for charging and data transfer. Here are some visual examples.
A USB-A Portable Drive
A smartphone with a USB-C Charging Port
Ref: BH Photo
Male (left) and Female (right)
USB-A are found in almost all modern computer. It is the most standard peripheral connector type. Many devices (such as mice and keyboards) have a built-in USB-A cable to connect them to a computer. USB-A is also used for memory sticks, chargers and many more different electrical peripherals.
There is also another variation called USB 3.0. They can be identified by the blue colour tip (instead of black) at the Male and Female connection point. It is 10 times faster than the USB 2.0 standard (the black one).
Ref: Cable Wholesale
USB 3.0. Top (Male) Bottom (Female)
Ref: Adafruit Industries
Male (left) Female (right)
USB-B is less common than USB-A. It is also a standard for peripheral devices. It is known for its bulky yet robust built. It is generally found on peripherals built-in for reliability. Devices with USB-B usually comes with a removable connector for USB-A connectivity. This is because most computers use USB-A. For instance, many printers come with a USB-B (female) port on the printer itself and also a USB-B (male) to USB-A (male) cable to connect the printer to a PC. USB-B cables are ubiquitous and cheap.
Male (left) Female (Right)
USB-Mini was the first attempt to reduce the size of USB connectors for smaller devices such as MP3 players and portable game consoles. It was generally used as a charger for smaller devices and also data transfers. The female is generally mounted on the device, and the small size is traded for with less robustness. USB-Mini is slowly phased out with the coming of USB-Micro.
Ref: RS Components
Male USB-Micro (left) Male USB-A (right)
USB-Micro is another standard focusing on reducing the size of a USB connector. Similarly to USB-Mini, it is small in size. USB-Micro adds an extra fifth contact for low-speed signalling, allowing it to be used in USB-OTG (On-the-go) applications. USB-OTG allows USB devices such as smartphones to act as a host allowing other USB devices to be attached to them. USB-Micro is commonly found in smartphones and digital cameras as a charging port.
USB 3.0 Micro-B Cable
USB-A 3.0 Male (left) USB Micro-B (right)
USB 3.0 Micro-B cables look similar to USB 2.0 Micro-B cables. However, USB 3.0 Micro-B includes additional contacts to carry data and power in USB SuperSpeed applications. It can be commonly found in devices that require high transfer speed such as portable hard drives.
USB 3.1 C
Ref: Velocity Micro
USB Type-C Male (left) USB-A 3.0 Male (right)
USB Type-C (AKA USB C) has 24 contacts in the connector. This version is also reversible, unlike the other variations of USB. The design of USB Type-C allows current above 500mA for your power-hungry devices. It is small yet powerful. Many peripherals that used USB-A are transitioning to USB-C. This allows for higher transfer speeds and more power. Most smartphones are also transitioning from USB-Micro to USB-C.
A Reversible USB-A
Ref: Droid Life
A Reversible USB-Micro
Fortunately, due to the advancements in technology, companies are manufacturing reversible USB connectors. This aids regular connects and disconnects of USB connectors as the orientation of which to enter does not need to be determined.
There are different standards for the different types of USBs. Not all USB types have different standards but the common ones such as USB-A and USB-C have. Here is a table differentiating them:
|Standard||Year Introduced||Connector Types||Max. Data Transfer Rate||Max. Cable Length|
|USB 1.1 (Full-Speed USB)||1998||USB-A, USB-B||12 Mbps||3m|
|USB 2.0 (Hi-Speed USB)||2000||USB-A. USB-B, USB-Micro, USB Micro B, USB Mini, USB-C||480 Mbps||5m|
|USB 3.2 Gen 1 (USB 3.0)||2008||USB-A, USB-B, USB-Micro B, USB-C||5 Gbps||3m|
|USB 3.2 Gen 2 (USB 3.1)||2013||USB-A, USB-B, USB-Micro B, USB-C||10 Gbps||3m|
|USB 3.2 Gen 2×2 (USB 3.2)||2017||USB-C||20 Gbps||3m|
|USB 4 (USB4 Gen 2×2)||2019||USB-C||20 Gbps||0.8m|
|USB 4 (USB4 Gen 3×2)||2019||USB-C||40 Gbps||0.8m|
Audio connectors are, as the name suggests, used to transmit audio from one device to another. It is usually from a device to an audio transmitter such as speakers or headphones. The two common ones are phone connectors and RCA connectors.
An earphone with mic with a TRSS 3.5mm connector
5.1 Speaker with RCA Jack
2.5mm, TS 3.5mm, TRS 3.5mm, 6.35mm
Phone connectors, AKA audio jack, are connectors that are very commonly used to transmit audio. They come in three different sizes: 2.5mm, 3.5mm and 6.35mm. They are typically used to transmit analogue audio from one device to another.
2.5mm are the least common in consumer products but are still regularly used in two-way radios (walky-talkies) and some video cameras.
3.5mm comes in three variations, TS, TRS and TRSS. TS are only capable of mono and unbalanced signals while TRS are capable of stereo. TRSS is used for audio devices with microphones attached such as a headphone with a built-in microphone.
TS vs TRS vs TRRS
6.35mm are used in many professional music applications such as connecting an electric guitar or bass through an amplifier. They typically come in TRS rather than TS.
The common availability of these connectors makes them good for most common consumer audio products.
RCA Male (left) RCA Female (right)
RCA was originally introduced for home phonographs. It typically consists of three headers: red for right audio, white/black for left audio and yellow for video. It can transmit both video and audio signals. It is becoming less popular due to the arrival of newer connectors such as HDMI. However, the ubiquity of these connectors allows them to still be found in many applications, mostly for home-built entertainment systems.
Ref: Computer Cable Store
HDMI Male (left, right)
HDMI is a common connector for sound and video. It is commonly found in TVs and monitors. All modern TVs and monitors come with HDMI slots to connect other devices to transmit audio and video.
These are connectors used specifically to provide power to devices. There are many variations but we’ll focus on the more common ones.
Here are some products you may check out:
Ref: RS Components
A PC power supply with an IEC Jack
Ref: Grow Win Limited
A laptop charger with Barrel Connector
A CPU fan with a Molex Connector
A rechargeable battery pack with a JST connector
These are the most common power connectors that can be found in household products and desktop PCs. There are many different variations such as IEC 60309, 60320, 60906-1, 62196, etc. The most common ones for consumer products are 60320. From IEC 60320, there are different variations as well.
IEC 60320 C5
IEC connectors are used mostly for AC power input. A major advantage is the ubiquity of IEC-to-wall cables.
Barrel Connectors (Coaxial Power Connector)
Barrel Connectors (AKA Coaxial Power Connector) are usually found in low-cost electronics which can be plugged into the wall power via AC wall adaptors. These wall adaptors can be found in many places, in a variety of power ratings and voltages. Barrel Connectors are commonly used for portable game consoles and laptop chargers.
The female barrel connectors can be purchased in several types: PCB mounted, cable mounted, or panel mounted. They are typically in-built into devices though. Some of these connectors have additional contacts to allow the device to detect the power supply and use its power instead of the in-built battery to save battery life.
Barrel connectors have different varieties, usually determined by their inner-diameter (the diameter of the pin inside the jack) and their outer-diameter (the diameter of the sleeve on the outside of the plug).
Molex Connector Female
Most computer drives, optical drives, graphics card, fans and other internal peripherals are obtained power through Molex connectors connected to the internal power supply. Molex connectors are designed to carry a lot of current: up to 11A per contact. It very common to power a machine with lots of power such as a CNC machine or a 3D printer.
The female and male distribution is a bit odd. The female is usually found at the end of a cable and plugged into a male connector inside of a plastic shell. The male connector is usually found built-in to the power supply or peripherals. They have low mating cycles as they are only designed to be plugged and unplugged a few times.
JST Connector Female (left) JST Connector Male (right)
JST connectors are commonly used for rechargeable battery packs, battery balancers, 3D printers and radio-controlled servos by hobbyists and consumers. Similar to Molex connectors, the female connector is usually found at the end of a cable and the males is inside of a plastic shell.
SMA Antenna Connectors
As the name suggests, they are used for antennas. There are two different kinds: SMA (Sub-Miniature Version A) and RP-SMA Connectors. RP stands for Reverse Polarity.
SMA: Developed in 1960, they are coaxial RF connectors
RP-SMA: A variation that reverses the gender of the interface
SMA connectors were used for WiFi devices for a long time. However, consumers were connecting SMA antennas to WiFi routers to achieve additional gains breaching a national regulation. Therefore, WiFi devices started using RP-SMA connectors.
SMA Connectors (not the RP one) have different variations of their own as well. These include a 3.5mm connector (rated up to 34 GHz) and a 2.92mm (rated up to 46GHz).
The only difference with the RP-SMA connectors is the centre pin, reversing the polarity of the connection, forming a “new standard”.
There are SMA to RP-SMA adapters and vice-versa that can be bought. Here is an example: RF Adapter RP-SMA Jack to SMA Plug
Pin Header Connectors
Pin Header connectors are widely used in electronic or instrumentation of PCB. It functions as a bridge between two PCBs. Typically, one side is soldered to a PCB either at a right-angle (straight) or parallel to the board’s surface.
Seeed’s Seeeduino V4.2 (ATMEGA328P) with 2.54mm single-row and double-row connectors
The most common pin headers are 2.54mm single or double row connectors as seen from the picture above. This is a standard breadboard compatible pitch and they come in male and female versions. These connectors are used to connect Arduinos boards and shields, and also jumper wires to breadboards.
There are other pitches as well which are not uncommon: XBee Chip Antenna uses a 2.0mm pitch version.
There are usually two types of cables to connect to these pin headers: individual write with crimp connectors or ribbon cables with insulation displacement connectors. The cables are generally female gender.
Crimp Type connectors
Seeed Studio’s Grove is the oldest and most established plug-and-play system. Popular among hobbyists, Grove takes a building block approach to assemble electronics. The Grove system consists of a base unit (stem) and various modules (twigs) with standardized connectors. The Base unit, generally a microprocessor, allows for easy connection of any input or output from the Grove modules. The base unit is not necessary as there is an adapter (Grove to Pin Header Converter) to run pins on Raspberry Pi or Arduino to Grove Connectors.
By having access to Grove Connectors, you can connect any of Grove sensors easily and conveniently to your Raspberry Pi or Arduino. There are sensors such as Accelerometer, Barometer, Gas Sensor, Light Sensor and many more.
Grove has only one type of cable, but that cable is capable of connecting I2C, Analog, digital and UART. Grove also has a branch cable that allows daisy-chaining of multiple Grove devices to a Grove shield.
Grove has an expansion board for Arduinos and Raspberry Pis with Grove connector to attach Grove Modules. There are Seeeduino Boards by Seeed which are Arduino compatible board with hardware changes. Seeeduino Boards comes with Grove connector built-in and are compatible with Arduino software, shields and IDEs.
Qwiic is SparkFun’s I2C prototyping system. Unline Grove, it’s only used for I2C devices. Similar to Grove, it also uses only one cable, a JST SH 4-pin connector. Qwiic also has adapters to connect Qwiic devices to Arduinos pin headers. Qwiic also allows daisy-chaining as most Qwiic devices have multiple Qwiic connectors to allow multiple devices. Qwiic also has shields and hats for Arduinos and Raspberry Pis. Similarly, Sparkfun also has Arduino compatible boards with Qwiic connectors.
Qwiic Cable – Breadboard Jumper
Qwiic Shield for Arduino
SparkFun Qwiic Pro Micro (ATmega32U4)
You can read more about SparkFun’s Qwiic system here!
STEMMA is Adafruit’s approach to a plug-and-play system. The main difference between STEMMA as compared to Grove and Qwiic is that STEMMA has three different types of connectors: STEMMA JST PH 3 Pin and 4 Pin connectors and STEMMA QT 4 Pin JST SH. STEMMA 3 pin JST PH is used for PWM, Analog and Digital. STEMMA 4 pin JST PH are larget 2.0mm pitch connectors for I2C use. STEMMA QT 4 Pin JST SH are smaller 1.0mm pitch connectors for I2C use as well when larger JST PH connectors won’t fit on the smaller board.
STEMMA 4 Pin JST PH
STEMMA 3 Pin JST PH
STEMMA QT 4 Pin JST SH
You can read more about STEMMA here!
Even though these three connectors are made by different companies, they are cross-compatible in some ways.
- Grove I2C Devices can be used with the larger STEMMA 4-pin cables and vice-versa
- Qwiic controller can be used with STEMMA and STEMMA QT devices as well. Qwiic devices can be used on a STEMMA controller as well if the voltage jumper is set from 5V to 3V.
- There are Qwiic Cable – Grove Adapter to allow Qwiic systems to be used with I2C based Grove devices.
Here are most of the common connectors that are ubiquitous. These are not all of the connectors that exist, but you can read more about connectors here:
- HDMI/Micro-HDMI vs DSI – Raspberry Pi 4 Display Connectors
- Tutorial: Intro to Grove Connectors for Arduino/Raspberry Pi Projects
Ultimately, how you pick which connectors to use depends on your application. The main factors to look out for are the:
- And Usage.
We hope this article will help you get a better understanding of the more common connectors.