Can Control Cables Be Used as AS-i Bus Cables?

March 9, 2021 Nils Jäger

I am often asked why AS-i bus cables are specially shaped and if it is possible to use a round 2×1.5mm² control cable . Therefore, it is worthwhile to take a closer look at the topic AS-i bus.

Where are AS-i bus cables used?

It is important to know where this bus system is used and why it was developed.

Actuator-Sensor-Box with AS-Interface connection

AS-Interface, or AS-i for short, is the abbreviation for Actuator-Sensor Interface. This bus system is intended to serve as an alternative to the conventional wiring of pushbuttons, I/O modules, safety door switches and valve terminals, for example. It simplifies the wiring effort and saves enormous time during installation. Where previously thick control cables had to be used, the two-core bus cable is now sufficient.

AS-i Bus Cables Are Easy to Connect

All you have to do it unscrew the housing, insert the cable, screw the housing back on and DONE!

It couldn’t be simpler. The transmission takes place via a two-core flat cable. This one is not shielded. In most cases, the required devices are connected to the cable via the insulation-penetrating technique. For this purpose, the housing of the device is unscrewed and the cable is inserted. Thanks to the special shape of the cable, reverse polarity protection is guaranteed and prevents incorrect connection of the cores. As soon as the housing of the subscriber is screwed back on, contact pins penetrate the cable and establish the connection. When commissioning, only the respective device has to be configured using software.

Diagram of an AS-Interface housing with insulation-penetrating connection technology

Two Cable Colors

There are two different AS-i bus cables. They differ not in form but in color. The yellow cable is for devices that require a low current consumption for their power supply. These can be pushbuttons or indicator lights, for example. Here both the bus signal and the power supply are transmitted via the same cores. For devices with higher power requirements, such as valve terminals, an additional black flat cable is used. This serves exclusively for power supply. Both cables are usually designed as 2x1.5mm² or 2x2.5mm².

Energy chain-compatible igus® chainflex AS-i bus cable CF898.082

Energy chain-compatible igus® chainflex AS-i bus cable CF898.083

Advantages

The AS-i bus system can be used flexibly and is very easy to install. No special electrical engineering training is required for this, therefore, even persons who have not received electrical instruction can connect the devices. This makes the AS-i bus economical and installation errors are reduced due to the reverse polarity protection. Due to the fact that many manufacturers, such as SICK, Siemens, Balluff, Festo, Turck and Pepperl+Fuchs, offer actuators and sensors with this interface, there is also high compatibility.

Control Cables as AS-i Bus Cables?

AS-i bus cables require no special electrical specifications. Therefore, control cables can also be used as AS-i bus cables. However, it must be taken into account that round cables usually cannot be connected directly to the bus devices. Nevertheless, in moving applications with extreme mechanical requirements it makes sense to use a control cable as an AS-i bus cable. Round cables have better durability inside cable carriers, as they are mechanically more stable due to the stranded cores and the round structure. Flat cables, on the other hand, turn in the carrier and lead to unequal push-pull stresses on the parallel running cores. This leads to core rupture and thus to machine failure. For most moving applications in energy chains, however, our chainflex® cables CF898.082 and CF898.083, which have been specifically developed for this application, can also be selected.

Learn more about chainflex® flexible cables here. You can also contact an igus® expert here with any questions. 

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