Fieldbus & Industrial Networking


Automotive electronics

January 2018 Fieldbus & Industrial Networking

Digital sensors return a discrete value of 0 or 1 to a controller. The controller, usually connected to I/O systems over a fieldbus, reads out the bus system data in a set cycle, commonly clocked in the millisecond range. Important to note here is that the bus system needs a degree of determinism and the controller must run in synchronisation with it, even if bus cycles are sometimes longer or shorter. With Beckhoff hardware and software, the synchronisation between controller and bus system are assured, as are the deterministic features of the ultra-fast EtherCAT communication system. This means that PC-based control provides the ideal foundation on which to implement oversampling technology.

Bus cycle subdivision with oversampling

Oversampling involves polling signals at a configurable multiple of the bus cycle time (i.e. in micro cycles) and writing the results to a temporary buffer. The set of process data collected is then transferred during the next bus cycle. Oversampling functionality can avoid situations like the following during signal polling: If, for example, a sensor is queried every 10 ms, only the data available at the precise time of the query is actually acquired. The controller is effectively blind from one query to the next, so details of any changes in the sensor’s state occurring between PLC queries are not recorded. For instance, a sensor’s state might switch from 0 to 1 and stay there for 9.9 ms. If it then reverts to 0, the sensor signal – from the perspective of the controller reading it out – will appear not to have changed at all over the 10 ms cycle.

Situations like this can be detected by using an EtherCAT oversampling input terminal such as the EL1262 to connect the sensor. This terminal is able to subdivide the bus cycle into as many as 1000 micro cycles. In the case of a 10 ms bus cycle, an oversampling factor of 1000 translates into a sampling interval of 10 µs. In a 1 ms bus cycle, a sampling interval of just 1 μs can be achieved, which is the shortest that EtherCAT oversampling terminals can currently support. This technology is ideal for reading out SENT sensors.

The pulse width encoding protocol: SENT

Single Edge Nibble Transmission (SENT) is a simple, unidirectional, asynchronous protocol that encodes sensor data based on the time between falling edges in a digital signal.

The pulse length describes the signal value transmitted. A single bit in the SENT protocol generally corresponds to 3 μs, which meets the minimum requirement in terms of sampling precision. The signal level is 5 V. The EL1262-0050 oversampling terminal meets both requirements in that it supports precise data acquisition down to 1 μs and is capable of processing the signal level directly. It can sample each bit of the SENT signal three times – more than enough to read the data transmitted in a signal pulse.

The data sets acquired are then processed in a ready-made function block, which evaluates the pulse lengths recorded, calculates the checksums and then marks the value either as valid or invalid.

The SENT protocol is mainly used for communication between sensors and electronic control units in vehicle electronics. Due to the simplicity of the protocol, the microcontrollers in ECUs are capable of evaluating it. SENT protocol receivers are not available for use in constructing measurement and test benches, but the open Beckhoff control system offers an alternative: The EL9505 power supply terminal can serve as the required 5 V power source, and the EL1262-0050 variant of the EtherCAT digital input terminal can be used to capture the sensor signal. In this way, SENT sensors can be directly and easily connected to the open and modular control platform from Beckhoff. This means that test benches equipped with Beckhoff technology can be used to conduct quality inspections on, say, throttle valve or steering torque sensors and make any necessary adjustments before the sensors are fitted to a vehicle.



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Ethernet connectivity for embedded systems
Fieldbus & Industrial Networking
Delivering Ethernet connectivity for embedded systems, XPort ETH Click is a compact add-on board from MIKROE, the embedded solutions company that dramatically cuts development time by providing innovative hardware and software products based on proven standards.

Read more...
Compact mini PC
Vepac Electronics Fieldbus & Industrial Networking
AS AAEON’s first Intel Core-powered PICO-SEMI system capable of fanless operation, the PICO-MTU4-SEMI from Vepac Electronics is easily deployed as part of larger equipment setups or integrated as the central unit of smart robotics solutions such as AGVs, AMRs and drones requiring minimal maintenance.

Read more...
PC-based control in window and door production
Beckhoff Automation Motion Control & Drives
Belgian machine builders CNC Solutions and Calvet are automating previously manual processes in aluminium window and door production. High-performance drive technology, motion control and electric cylinders from Beckhoff proved crucial in equipping the machine with the necessary finesse when pressing the window frames.

Read more...
Future-ready I/O to redefine connectivity
Schneider Electric South Africa Fieldbus & Industrial Networking
Schneider Electric South Africa has launched its state-of-the-art Modicon Edge I/O NTS. This future-ready I/O redefines connectivity, data aggregation and operational efficiency for industrial applications.

Read more...
Referro Systems delivers industrial connectivity
Fieldbus & Industrial Networking
To meet the growing demand for secure, flexible and reliable remote access for industrial network connectivity for its clients, Referro Systems has added Rockwell Automation’s Stratix 4300 to its inventory of products.

Read more...
Case History 199: Another example of the effectiveness of cascade control
Michael Brown Control Engineering Editor's Choice Fieldbus & Industrial Networking
In my last article I wrote about how cascade control systems can effectively overcome valve problems. This article gives another example of how a temperature control was able to perform well, in spite of really severe valve problems.

Read more...
Upgrading legacy automation
Omron Electronics Editor's Choice Fieldbus & Industrial Networking
Legacy automation is characterised by technology in the later stages of its useful life. As new automation technologies continue to emerge and interconnect at an exponential rate, failing to integrate these technologies can widen the gap between the competitive and the obsolete.

Read more...
A one-stop-shop for industrial
Fieldbus & Industrial Networking
HMS Networks has announced that Red Lion and N-Tron are officially product brands. For thousands of automation engineers and system integrators worldwide, this means that scalable industrial solutions for cloud connectivity, edge intelligence, asset management, industrial Ethernet switches, panel meters and operator panels are now available from one trusted source.

Read more...
Power over Ethernet (PoE) injector for seamless deployment
Vepac Electronics Fieldbus & Industrial Networking
The Edimax GP-203IT from Vepac Electronics is a Power over Ethernet injector that not only delivers a cost-effective solution for power distribution, but also enables seamless deployment on the existing LAN infrastructure.

Read more...
A one-stop-shop for industrial communication
Fieldbus & Industrial Networking
HMS Networks has announced that Red Lion and N-Tron are officially product brands. For thousands of automation engineers and system integrators worldwide, this means that scalable industrial solutions for cloud connectivity, edge intelligence, asset management, industrial Ethernet switches, panel meters and operator panels are now available from one trusted source.

Read more...









While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.




© Technews Publishing (Pty) Ltd | All Rights Reserved