Banana & Fork Plugs
(1 763)Banana plugs and fork terminals
Everyone, even a novice electronics technician or hobbyist, has encountered banana and fork connectors. They are commonly used in schools and during educational classes, in various branches of automation and electronics, but especially in measuring devices such as multimeters, all kinds of power supplies, such as adjustable lab power supplies, but also in Hi-Fi loudspeakers. Their widespread use is related to their simplicity of application, provision of good electrical conductivity, and the speed with which connections can be made between specific electronic components and/or measuring devices.
What are banana plugs?
Banana plugs can have different designs, but most often have a tip in the form of a cylinder, which is cut parallel to its axis of rotation. Thanks to these cuts, plates are formed, which, when properly bent, make up a kind of spring that spreads the cylindrical surface of the tip when placed in a designated socket. This provides a large contact surface area, and thus a good electrical connection that has low resistance and a high current that it can conduct without generating excessive heat, which can lead to so-called contact burnout. Therefore, is it recommended to use banana plugs? Of course, it depends on the specific case, but everywhere where a fast and fairly reliable connection is required, which if necessary can be efficiently switched to another socket, a banana plug will work perfectly.
Function of the fork terminals
Fork terminals perform almost the same function as the ring terminal, but instead of a closed loop, they have an open loop as an electrical contact. The advantage of this solution is faster electrical connection when needed, e.g. for testing particular device, because it is not necessary to completely unscrew the screw forming the clamp, e.g. as it is often seen in switching power supplies, in order to put an ring through it. A few turns of the screwdriver are enough to make the fork terminal fit and put under the head of the screw or a special plate. The obvious disadvantage of this solution is less resistance to the possibility of unplugging such a connector from the socket, although such a risk, with a well tightened clamping screw, is still quite small. However, for safety reasons, it is a good idea to replace any fork terminals in the final device with ring terminals, to make sure that none of the connections created in this way are disrupted.
Therefore, is it better to use banana plugs or fork terminals? Since they fulfil the same function, i.e. provide effective electrical connection, the choice depends on the user's preference, the resistance requirements against unintentional cable yanking, but above all on the current value they will conduct. Fork terminals will rather be used with power sources, while banana plugs will be used with measuring devices, such as multimeters. Of course, if necessary, you can also use banana plugs for connections to power supply terminals, which is often the case with laboratory power supplies. Both types of plugs are often used in one device.
How to connect a banana plug or a fork terminal?
How to connect these terminals depends on the specific model, but it is nothing difficult. One of the simplest types of connecting a plug or tip to a wire involves placing the uninsulated end of the wire into a proper socket and tightening a small screw to create some electrical contact. Another solution is plugs whose tip is a threaded rod. In this case, it is good if the end of the wire has an ring terminal crimped on it. The ring is put through the screw thread and tightened with a nut, creating a secure connection. Similar to them are panel-mounted plugs, which can be attached (screwed) to the PCB or the housing of the device. Another popular category comprises soldered terminals. For this purpose, you need a high-power soldering iron, set to a high temperature value, because the heat will very quickly spread throughout the volume of the plug, efficiently cooling the soldered place and making the whole process more difficult. The end of the wire to be soldered should be tinned beforehand to make it easier to solder. This is the most popular solution. Depending on the way of connecting the plug to the socket, there are plugs with screw, push-in, crimp, or plug-in mounting.
Banana and fork connectors – choice
When choosing the right plug, you should pay attention to several parameters. The first of them is the type of terminal, or in fact its mechanical compatibility with the socket. Among the banana plugs, the most popular sizes are 2mm and 4mm, although you can also find 1.5mm and 2.4mm. Among the fork terminals, the most common are those with a spacing of 6mm and 8mm. Sometimes the overall length of the plug can also be important, varying from about 35mm to about 60mm.
Another very important parameter is the rated current, which you can use to charge a given plug without having to worry that you will release too much heat on it and before its so-called burning. For 2mm banana plugs, these will be currents from about 5A to over 30A. For 4mm banana plugs, the upper range will be at a level of over 40A. Fork terminals will have a similar load capacity. But do not forget that, in addition to the plug, the current-carrying capacity of the cable connected to it is equally important. In this case, the principle stating that the chain is only as strong as its weakest link applies. If we choose a plug with a load capacity of several dozen amperes, but it will be connected to a cable with a load capacity of only a few amperes, the plug will be much oversized in relation to the cable. On the other hand, it may lead to a situation when a cable prepared in this way will be loaded with current, which will burn its insulation.
When choosing the right plug you should also check its voltage rating. Non-insulated sockets and plugs can be used during the operations in which the voltage will not exceed 60V DC. If a current with a higher voltage value will flow or such a flow is possible even for some time only, sockets and plugs must be properly protected, so that there is no possibility of touching the unprotected element. Information regarding the safety category and permitted operating voltage is available in the product descriptions. An improperly selected insulation class may cause overvoltage and damage to any connected electronic components.
The most popular insulation colours are black and red. It is recommended to stick to the generally accepted rule according to which black stands for neutral ground, and red for positive voltage. Of course, the cables can be swapped as you like, but it probably won't be intuitive for someone who hasn't worked with the given connection system, so it can create a dangerous situation for the user, as well as for the powered components. Sometimes green or yellow-green is additionally used for ground, but you can also find a connector with white, blue, brown, purple, grey, orange, or yellow insulation.
Banana plugs with insulated and uninsulated connectors
Among the banana plugs, we can distinguish those with insulated and uninsulated connectors. Plugs with insulated connectors can only be connected to their corresponding sockets. They are not compatible with sockets for non-insulated plugs. This insulation ensures protection against accidental short-circuit or electric shock, therefore, especially in measuring equipment, this type of connectors are used. We would like to remind you that uninsulated plugs can only be used when working with safe voltage. Banana plugs can also be available as angled, double, with additional transverse or axial sockets, as well as with a sliding cover.
As an accessory, you can also find adapters: from fork terminals to banana plugs, from 4mm banana plugs to 2mm banana plugs and vice versa, as well as shorting plugs.
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