April 7, 2020
Robust miniature connectors for extremely compact control systems
ERNI SMC connectors connect and power Sigmatek S-DIAS modules.
When developing the highly compact S-DIAS control and I/O system from Sigmatek, the aim was to use the installation space in the control cabinet or in the machines as efficiently and optimally as possible for the application. This is why, in addition to the extraordinarily compact design, a modular concept was chosen. The result is very narrow control modules measuring only 12.5 mm wide. The extremely slim modules are powered and connected to the bus via robust, miniaturized multi-contact connectors. The DIN rail modules communicate with each other via the ultra-fast Varan real-time Ethernet bus at 100 Mbit/s. The objective here was to find a suitable compact connector for this and for the power supply that would meet the demanding space concept as well as the speed and robustness requirements. A high number of pins in a small space was a basic requirement and the impedance controlled signals were to be transmitted safely and without interference. ERNI's SMC connector in a 1.27mm pitch met all these requirements.
High density, reliable and robust
The S-DIAS control system combines fast signal processing, simple handling, high vibration resistance and scalable modularity in an extremely compact design. This allows space-critical applications to be addressed, where previously often only special PCB solutions with limited expandability were used. The high component density helps machine and plant manufacturers to master the growing complexity of their machines while maintaining the same control cabinet volume. The concept was made possible by using the extremely compact SMC connectors, which not only connect the modules to each other reliably and at high data rates, but also guarantee that the modules are safely supplied with power. For example, the Varan bus connection between the various S-DIAS modules is implemented via the two-row SMC connectors in such a way that the performance of the Varan bus can be used without restrictions.
For the modular S-DIAS concept, not only the modules with high component density are decisive, but also their secure and robust connection to each other. Therefore a connector was needed that had to meet various – often contradictory – criteria. Basically, the connector naturally had to offer the required stack height in relation to the 12.5mm pitch and support a data rate of 100Mbit/s (Varan Bus) with sufficient margin. Another important criterion were the requirements for shock and vibration resistance with 15g and 1g in the range of 8.4 to 150Hz. The connector was designed to be used for both the module bus differential signals and the power supply (+24 V/max. 1.6 A; +5V /max.1.6 A) of the I/O modules. This meant that a corresponding current carrying capacity was also required. In the end, the impedance of the module bus had to be 100 ohms. Sigmatek opted for ERNI's SMC connector, whose specifications meet all the criteria mentioned.
Compact without restrictions
Limited space, yet high performance requirements are typical for many industrial controllers, such as the S-DIAS family. The plug connections must also take this into account. Accordingly, compact, safe and reliable connectors with high signal integrity and high current carrying capacity are required. Increasing device functionality/integration requires higher data rates, higher numbers of pins and smaller pitch dimensions. The comprehensive SMC portfolio combines all these often conflicting requirements and offers a wide range of solutions. The main design criteria of the SMC series are the dual-beam spring contact principle for very good contact properties and extremely reliable contact security, a high-temperature-resistant insulating body with polarisation and insertion chamfers, and the very large wipe length. The optimized contact design has an almost continuous impedance curve and, with the appropriate design, allows the secure transmission (differential) of data rates up to 3Gbit/s.
Many customers prefer SMT as a termination method and reflow soldering processes. When using connectors with a very small pitch, particular attention must be paid to reliable processing.
To meet the industrial vibration and shock requirements, double-sided contacting (with vibration/shock tests up to 20g/50g) offers undisputed advantages.
The highly reliable small multiple connector (SMC) family of connectors is available in various designs, such as straight and right-angled male and female connectors as well as a low-profile version. SMC connectors require little space and offer high contact density. A full metal SMT bracket also absorbs high insertion and withdrawal forces. The combination of male and female connectors of different heights results in a range of board-to-board distances (8mm to 40mm). The available number of pins ranges from 12 to 80.