Power Supply Screw Terminals: Standard Sizes For Frames

Screw terminals are electrical connectors that enable wires to be connected directly to a PCB. They consist of a metal frame and a screw. The screw terminal is secured to the PCB using mounting legs that are snapped into holes on the PCB and soldered into place. Pre-stripped wire is wrapped under the head of the screw and tightened with a screwdriver, creating a secure electrical connection between the wire and the metal frame. Screw terminals are commonly used to connect a chassis ground, such as on a record player or surge protector. The ATX standard for screw size in power supplies is 6-32.

Screw terminals are electrical connectors made from plated brass

To use a screw terminal, the wire is pre-stripped and wrapped under the head of the screw, which is then tightened down using a screwdriver. This creates a secure electrical connection between the wire and the metal frame. Screw terminals can be used with solid, stranded, and pre-terminated wire. They are also simple to use, requiring only basic hand tools for installation and removal.

Screw terminals are commonly used to connect a chassis ground, such as on a record player or surge protector. They are also used extensively in building wiring for the distribution of electricity, connecting electrical outlets, luminaires, and switches to the mains. In addition, screw terminals are often used for speakers in public address systems and for major appliances such as clothes dryers and ovens that draw more than 15 amperes.

Screw terminals offer several benefits, including low cost, ease of use, and the ability to create secure electrical connections. They can also be reused, allowing for the replacement of wires or equipment. However, they may require more time for installation compared to plug-in connectors, as the wire must be stripped and properly wrapped around the screw head.

Screw terminals are secured to the PCB using mounting legs

Screw terminals are a type of electrical connector that enables wires to be connected directly to a PCB. They are made from plated brass and consist of a metal frame and a screw. Screw terminals are secured to the PCB using mounting legs, which are snapped into holes on the PCB and soldered into place. This method of connection is simple and cost-effective, as it eliminates the need for a mating connector. It also provides a secure electrical connection between the wire and the metal frame.

The process of connecting wires to screw terminals is straightforward. Pre-stripped wire is wrapped under the head of the screw, and a screwdriver is used to tighten it down, creating a solid electrical and mechanical connection. This type of connection is more reliable than soldering, as it prevents wires from loosening due to vibration or thermal cycling. It also allows for individual wires to be easily unscrewed and re-secured for maintenance and repairs.

Screw terminals are commonly used in various applications, such as connecting panel wiring in industrial control boxes, sensor and actuator cables interfacing with boards, and field-installable wiring on telecom or server equipment. They are also useful for prototyping during development, as they provide a quick and easy way to connect wires.

Overall, screw terminals secured to the PCB using mounting legs offer a convenient, reliable, and flexible solution for connecting wires and cables to PCBs. They simplify field wiring and provide a robust connection that is resistant to vibration.

Screw terminals can be used with solid, stranded and pre-terminated wire

Screw terminals can be used with solid, stranded, and pre-terminated wire. Here are some detailed instructions and considerations for each type of wire:

Solid Wire

Solid wire conductors are commonly used in alarm and telephone applications. When terminating solid wire with screw terminals, it is essential to strip the insulation from the wire, exposing the conductor. The exposed conductor should be twisted tightly and folded neatly to provide a secure connection. It is also recommended to leave some slack in the wire to allow for re-termination if the strands break due to repeated insertion. Using screw terminals with protective tongues can also enhance the security of the connection.

Stranded Wire

Stranded wire offers more flexibility than solid wire and is commonly used in applications where vibration or movement is present. To terminate stranded wire with screw terminals, it is recommended to strip and twist the wire tightly. The twisted wire can then be folded back onto the insulation, creating a loop that can be clamped securely by the screw terminal. This method helps to maximize the number of strands in contact with the terminal, improving the electrical connection.

Additionally, it is essential to select the appropriate screw terminal size for the stranded wire. If the wire is too small for the terminal, the connection may be loose, resulting in high resistance or heat buildup. Using a spring clamp terminal or a wire ferrule can also enhance the security of the connection. A wire ferrule is a metal sleeve that slides over the strands and is crimped in place, providing a solid end that can be clamped securely by the screw terminal.

Pre-Terminated Wire

Pre-terminated wire comes with connectors or terminals already attached, offering convenience and time savings during installation. When using pre-terminated wire with screw terminals, it is crucial to match the correct plug and socket types. Pre-terminated wire often comes with male and female connectors, which must be properly paired to ensure a secure connection. Additionally, pre-insulated wire end terminals can provide strain relief and protect the wire from the turning screw, reducing the risk of damage.

In conclusion, screw terminals offer versatility and can be used with solid, stranded, and pre-terminated wire. By following the appropriate techniques for each wire type, a secure and reliable connection can be achieved. It is important to consider the specific application and select the suitable wire type and termination method to ensure optimal performance and safety.

Screw size for power supply backing plates

The standard screw size for power supply backing plates is 6-32, which is the ATX standard. This refers to a thread diameter of #6 and 32 threads per inch. The pitch of the screw head is 0.794" and the diameter is 1/4".

The #6-32 UNC is a Unified Thread Standard (UTS) screw, specifying a major thread diameter of #6, which is defined as 0.1380 inches (3.51 mm), and 32 threads per inch (tpi), which equates to a thread pitch of 0.031250 inches (0.7938 mm).

The #6-32 UNC is used to secure a power supply to a computer case. It is the most common screw found inside computer cases and is usually provided with a #2 Phillips drive. It is also often used to secure a 3.5-inch hard disk drive to the case, hold an expansion card in place, fasten case components together, and hold the main cover on the case.

The #6-32 UNC is a thicker screw with a coarse thread, making it suitable for fastening larger parts and thicker materials. Its larger size and coarse thread make it easier to work with during assembly, reducing the risk of cross-threading.

Other types of screws used in computer cases include the M3, which is the second most common, and the #4-40 UNC, which is used for fastening certain connectors to hardware ports.

Screw terminals are used for connecting electrical outlets

Screw terminals are a type of electrical connection where a wire is held in place by the tightening of a screw. They are commonly used for connecting electrical outlets, as well as luminaires and switches to the mains. They are also used for directly connecting major appliances such as clothes dryers and ovens that draw in excess of 15 amperes.

Screw terminals are considered more secure than push-in wire connections, which can loosen over time and cause arcing, pitting, sparking, and a buildup of heat. Screw terminals, on the other hand, provide a tighter connection that prevents wires from coming loose and creates a better electrical connection.

To make a screw terminal connection, you must first strip about 3/4 inch of wire insulation from the conductor. Then, use long-nosed pliers to bend the exposed metal tip of the wire into a J-shaped hook. This hook will be looped around the screw terminal in a clockwise direction, so that when the screw is tightened, the wire is pulled closed rather than forced open.

It is important to connect the right wires to the correct screw terminals. On a receptacle, the bronze or brass-coloured screw terminals are for hot wires (black or red insulation), while the silver-coloured screw terminals are for neutral circuit wires (white insulation). The green-coloured screw terminal is for the circuit grounding wire, which is usually a bare copper wire or a wire with green insulation.

Once the wire is hooked and looped correctly, the screw terminal can be tightened firmly down onto the wire, ensuring that no wire insulation is under the head of the screw and that the bare wire is not touching any part of the plastic housing.

Frequently asked questions