Connectors By Tim Surtell

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There are many situations, particularly with large models, where it is advantageous to be able to remove parts of a model for easy access or transportation. If the model uses electrical components, you will likely have the need to join wires from components in a detachable part of the model to wires in another, and will need to choose an appropriate connector.

This article will introduce you to some of the common connectors that are available. Before you decide on which connector to use, always remember to check that it has a high enough current rating for your intended use.

Single Way Connectors

Single way connectors allow for only one join and so are generally used in applications where only a few joins are needed, such as when testing circuits, or as the two power supply unit connections to a model, or for connections that are frequently moved around (as in some designs of control panel).

Banana Connectors

The most robust type of single pole connector is the banana connector, so-named because of the shape of its plug's spring. You will find there are many different designs incorporating one or more of the following characteristics:

• A plug with a 4mm diameter (the standard size) or a 2mm diameter.
• A plug with an integrated socket, so that plugs can be easily stacked on top of each other.
• A panel-mountable socket (usually requiring an 8mm diameter hole).
• A panel-mountable socket integrated into a screw terminal post, or set of two posts (red and black for power connections).
• A PCB-mountable socket, either a simple cylinder that is soldered in place, or a side-facing socket.
• Wire connection via a screw terminal or a solder tag.

Banana connectors are available in many colours and you can even buy coloured patch cords which are ready-made with one banana plug on each end.

Multi Way Connectors

A wide range of connectors are available for joining two or more wires, with each being suited to a specific application. Here are a few common ones that might be useful in Meccano models:

Barrel Connectors

Ideal for connecting a low-voltage power supply unit to a model, barrel connectors which join two wires are a good choice as their design will help avoid shorting out the power supply unit by accident. Normally the outer part of the barrel is connected to 0V on the power supply unit.

You will find there are many different designs incorporating one or more of the following characteristics:

• A plug with an inside diameter of 2.1mm (the standard size) or one of a number of other larger or smaller inside and outside diameters. Plugs are also available in various shaft lengths.
• A plug with a strain-relief sleeve and clamp to protect the wire.
• A panel-mountable socket.
• A PCB or stripboard-mountable socket.
• Sockets with an extra break contact so that is it is possible for a circuit to know when the plug has been inserted.
• Wire connection via a solder tag.

DIN Connectors

Generally used for connections in audio systems, DIN (which stands for Deutsches Institut für Normung, the German Institute for Standardisation) connectors are circular and come in 2 to 8 way designs, making them useful as a compact connector for models like cranes. The wires are connected via solder tags and the plug has a strain-relief sleeve and clamp to protect the wires. The sockets are either in-line or panel-mountable.

Terminal Blocks

Good for making semi-permanent joins in high-current applications, terminal blocks come in many different designs, some of which are:

• Terminal block strips with two screw terminals for joining two wires together. Can be cut down if a smaller number of ways is required.
• PCB or stripboard-mountable blocks with pins at 0.2" pitch and side-facing or 45° screw terminals. Can be interlinked if a larger number of ways is required.
• PCB or stripboard-mountable blocks with pins at 0.2" pitch and side-facing screw-less terminals. Can be interlinked if a larger number of ways is required.
• Pluggable blocks with screw terminals.

PCB Connectors

While cheap, these connectors are not very robust and can be awkward to assemble, making them only really suitable for low-current applications inside models where they will be rarely disconnected.

The connectors come in three parts: PCB pins, a socket housing and socket terminals.

The PCB pins are mounted 0.1" apart in a plastic spacer and are soldered onto a PCB or piece of stripboard. Any number of pins can be used by simply snapping them off, but the number of connections is limited by the socket housing. Polarised PCB pin headers are also available so that the connection cannot be accidentally made the wrong way around.

The socket housing can be purchased in sizes ranging from 2 to 17 way, and has slots for inserting the socket terminals. These terminals have a spring at one end which engages with the PCB pins, and an area at the other end to solder or crimp a wire.

D-Sub Connectors

If you need to make several low-current connections, a D-Sub connector might be suitable as they are available in 9 to 25 way designs. Wires are connected inside to two rows of solder tags, and the hoods, purchased separately, normally have a strain-relief sleeve and clamp to protect the cable.

 Shopping List

Below is a list of some of the connectors which were discussed in this article.

Part Description		Quantity Required		Rapid Code		Unit Price		Total Price
10-way PCB Socket Housing		1		22-0940		£0.53		£0.53
10-way Straight Plug PCB Header		1		22-0985		£0.93		£0.93
12-way 3A Terminal Block Strip		1		21-0100		£2.39		£2.39
15-way D-Sub Plug		1		15-0105		£1.36		£1.36
15-way D-Sub Snap-Lock Hood		1		15-0860		£2.59		£2.59
15-way D-Sub Socket		1		15-0155		£1.36		£1.36
2.1mm/5.5mm Panel Mounting Barrel Socket		1		20-1094		£1.61		£1.61
2.1mm/5.5mm PCB Mounting Barrel Socket		1		20-0970		£0.41		£0.41
2.1mm/5.5mm/9.5mm Barrel Plug		1		20-0905		£0.61		£0.61
25-way D-Sub Plug		1		15-0110		£1.68		£1.68
25-way D-Sub Snap-Lock Hood		1		15-0930		£3.55		£3.55
25-way D-Sub Socket		1		15-0160		£1.62		£1.62
2-way PCB Mounting Terminal Block		1		21-0471		£0.20		£0.20
2-way PCB Socket Housing		1		22-0905		£0.11		£0.11
2-way Straight Plug PCB Header		1		22-0950		£0.21		£0.21
3-way DIN Plug		1		20-0240		£1.12		£1.12
3-way DIN Socket		1		20-0245		£0.88		£0.88
3-way PCB Mounting Terminal Block		1		21-0473		£0.29		£0.29
3-way PCB Socket Housing		1		22-0910		£0.15		£0.15
3-way Straight Plug PCB Header		1		22-0955		£0.32		£0.32
4mm Black Banana Plug with Integrated Socket		1		17-0400		£1.25		£1.25
4mm Black Banana Socket		1		17-1920		£0.90		£0.90
4mm Black Patch Cord with Banana Plugs		1		17-2286		£6.70		£6.70
4mm Red Banana Plug with Integrated Socket		1		17-0420		£1.51		£1.51
4mm Red Banana Socket		1		17-1935		£0.62		£0.62
4mm Red Patch Cord with Banana Plugs		1		17-2280		£6.62		£6.62
4mm Terminal Posts with Integrated Banana Sockets		1		-		£0.00		£0.00
4-way DIN Plug		1		20-0260		£0.98		£0.98
4-way DIN Socket		1		54-5559		£5.98		£5.98
4-way PCB Socket Housing		1		22-0915		£0.20		£0.20
4-way Straight Plug PCB Header		1		22-0960		£0.41		£0.41
5-way DIN Plug		1		20-0250		£2.04		£2.04
5-way DIN Socket		1		20-0314		£0.69		£0.69
6-way DIN Plug		1		20-0280		£0.93		£0.93
6-way DIN Socket		1		20-0375		£0.97		£0.97
7-way DIN Plug		1		20-0290		£1.24		£1.24
7-way DIN Socket		1		20-0316		£0.96		£0.96
8-way DIN Plug		1		20-0295		£0.86		£0.86
8-way DIN Socket		1		49-4754		£1.78		£1.78
9-way D-Sub Plug		1		15-0100		£0.96		£0.96
9-way D-Sub Snap-Lock Hood		1		15-0800		£1.87		£1.87
9-way D-Sub Socket		1		15-0150		£1.00		£1.00
PCB Pins		1		54-3907		£1.94 (per strip of 36)		£1.94
PCB Socket Terminals		1		22-1098		£35.64 (per strip of 1000)		£35.64
Grand Total								£97.97

Full printer-friendly parts list

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Orders can also be placed by telephoning Rapid on 01206 751 166 or visiting their website at www.rapidonline.com. Prices quoted include VAT at 20%.

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Article Information Topic: Practical Matters | Created: 05/02/2007 | Last modified: 09/02/2007 | First published in EiM: Issue 4 (June 1999)

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