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This inflexibility is almost inevitable, since no single interface can accommodate different needs, such as thermocouple switching and high-power contactor coils. Since providing an optimized pluggable interface is considered too expensive a feature for standard industrial controllers, there are no “easy solutions” in the controller. Combined with the need to quickly and easily replace worn or damaged interfaces, this means that the use of external interface relay modules has become the de facto solution.
Various styles of relay interface modules are now available to bridge the gap between industrial controllers and a growing number of real-world control scenarios. At one time, the most common method was to simply combine multiple PCB relays onto a single board and mount them on a 35mm rail. This can be useful, for example, when you need to increase the current rating on the output block, but it makes it difficult to configure the output between channels, and is also quite bulky and takes up a lot of panel space.
Today, the preferred solutions are ultra-thin single-pole modules, especially those equipped with replaceable relay elements. Here, different versions can be selected for each channel to suit specific load requirements without going over or under specification. Replaceable relay types also provide quick and easy servicing where ultra-long service life is important.
This approach has been designed to provide additional cost and time savings through innovations such as multi-pin jumpers for simple common circuit connections between adjacent relay interface modules, and the inclusion of identification tags for ease of commissioning and maintenance.
Over time, interface relays became “full-featured” off-the-shelf components, including relays and sockets, with associated coil indication and suppression built-in. If it is necessary to connect several devices from one controller output, multi-pole relay interface modules can be used with little waste of panel space.
By defining a relatively limited number of relay/socket/module combinations and assigning a part number to each combination, Finder has long provided design engineers with a range of perfectly matched components that are assembled and ready to connect—often. Offers the added benefit of cost savings. inventory, procurement time and costs.
Until recently, this family of relay interface modules consisted of seven product types, each with its own core functionality, satisfying the following design considerations:
- Selection of contact materials: from gold plating for high reliability low level switches to silver tin oxide for high current surge applications such as lighting.
- Choose between electromechanical relays (for their isolation and ease of use) and solid-state relays (for their life cycle and switching speed).
All interface relays are available for 35mm rail mounting, and some are also available for direct chassis mounting. All products feature built-in coil indication LEDs for immediate status identification, simplified diagnostics and built-in relay coil back-EMF suppression.
Despite the popularity and flexibility of these devices, there are small but significant differences in the ideal feature set of an interface relay depending on whether the device is located on the input or output side of the controller. To date, this aspect of design has not been fully considered.
With this in mind, Finder has developed and recently released a new line of relay interface modules called the Master 39 Series. A descendant of the successful ultra-thin 38 series, which met the mainstream market’s requirements for unipolar devices, this latest series features an innovative terminal arrangement that makes connecting input and output devices particularly simple and cost-effective, and also has the unique feature of integrated, replaceable fuses. output circuit.
The “Master” product line options are for general use (“Basic”, “Plus” and “Timer”), and then specifically for the output interface (“Output”) and the input interface (“Input”):
The Master Basic Relay Interface Module does not have output fuses or additional common terminals. In this sense, it is specialized for neither and can serve as both input and output, although the user may have to provide additional termination points.
The Master Plus relay interface module (Fig. 1) is an upgraded version of the Master Basic, the main difference of which is the additional fuse in the output circuit. It also has a wider input voltage range than the Master Basic and is also available in a leakage current suppression version for 125 and 230 VAC.
The Main Output Interface Module is designed to easily and efficiently connect multiple loads, such as solenoid valves or similar loads. The PLC or similar controller switches the interface relay coils in the usual manner. Load circuit power is distributed to all modules via a simple jumper inserted into terminal 11 (terminal 13 for SSR versions). A live switch for each load is available on terminal 14 of each module and the return power is distributed to all modules via another jumper which can then be connected to each load on the BB terminal of each module. As a result, wiring and connecting each load is simple and efficient, since both the overall power connection and the individual switch wires are connected locally to the appropriate interface module.
The Basic Input Interface Module (Figure 2) is designed to easily and efficiently connect multiple input devices, such as traditional mechanical switches, 2- or 3-wire proximity sensors, or similar devices. Positive switch/sensor power can be efficiently distributed across all modules using jumpers, which can then be connected to each input device at the BB terminal on each module.
Using a jumper, the negative terminal of the power supply can be easily distributed to all common relay coil A2 connectors of each interface module. 3-wire sensors must receive the same negative wire, and the negative wire of the sensor can be connected directly to the A2 terminal of the appropriate module (2-wire switches and sensors do not require this connection). The positive switch of each switch/sensor is connected to terminal A1, which supplies power to the interface relay coil.
As with the main output interface module, wiring and connecting each input switch/sensor is simple and efficient, since both the overall power connection and the individual switch wires are connected locally to the corresponding interface module.
The main timer (Figure 3) is primarily used to add a manually configurable multi-function timer function to a PLC/controller input or output. This is especially useful when the time delay needs to be adjusted locally or when it is later discovered that a time delay is required and reprogramming the PLC is not a short or long term option. The main timer also has an additional output fuse module.
The Master 39 Series offers electromechanical and solid state relays that are currently available in screw terminal versions, but screwless terminal versions will soon be available. Versions with a circuit option that suppresses input coil leakage current may be a solution for applications where high levels of leakage current are present in the coil circuit even when the circuit should be closed. For example, long cables as well as old PLC triac outputs can create these induced currents. These special types of current suppression interface relays provide an effective countermeasure.
New generations of relay interface modules, such as the Master 39 Series Finder modules, offer a more flexible approach to meeting the often conflicting needs of today’s more demanding industrial automation environments. This series offers a selection of simple, ready-to-assemble relay/socket combinations with a wide range of advanced operating features, such as fused output circuits and auxiliary terminals to efficiently connect multiple input and output devices.
Post time: May-06-2024