There is always a Voltage drop on a wire if current runs through it. So if you start at the central unit (power supply) with 12V after a long distance (for example 100 meter of AUTOBUS cable) there may be only 10V left. This depends on the resistor of the power supply wires (the are each 1mm²) and the total current taken from the TELETASK power supply (TDS10132 or TDS10134). That is not such a problem because you can’t avoid, but every interface needs at least 9V to operate properly.
The screen capture above is from PROSOFT (TELETASK configuration software) in the ‘interfaces’ menu. Every interface (in general the generation 2015 and later) measures his own power supply Voltage and send it to PROSOFT. Older interfaces don’t show information in that column (like 3th row in the screen capture example above).
Here you can see from this example that the other interfaces all have supply Voltage above 9V so that is OK.
But how can you predict if this going to be ok or not?
That is more complicated. Therefore, in every data sheets of every product you can find the current consumption of an interface. If you use the maximum consumption and you know where on the cable this interface will be connected, you can calculate <hat the Voltage drop will be at the furthest interface; If that Voltage is above 9V then all the other interface which are installed before that point, will have a higher Voltage and will be OK as well.
To make this calculation more simple, we have made an Excel spreadsheet. This sheet contains all our interfaces and their current consumption. You only have to select the proper interfaces which you plan to use and how long the AUTOBUS cable is between the former interface and the next.
So if the first interface is a 2 button AURUS_2 and he is connected to the central unit with an AUITOBUS cable which is about 10 meter long, you define the interface first in de sheet and also add 10 meter length. And you do the same for all other interfaces. At the end, you will see if the Voltage will be enough (above 9V) or not. If it comes near to 9V or drops below of it, you need to provide an extra power supply somewhere before that interface. This extra power supply (TDS10132 or TDS10134) will make a new 12V again and you can go on with connecting interfaces (see schematic below, on how to connect an extra power supply).
IMPORTANT 2 : (see also the TELETASK system training): If you an extra power supply, all AUTOBUS wires are fed to the next interface, except for the ‘+’ wire. This one has a dropped Voltage and can’t be used. It is the new ‘+’ from the extra power supply which is used to the remaining interfaces.In the training there is a drawing illustrating this.
There is also a tab on calculation of the Voltage drop on an installation of technical interfaces in the electrical cabinet. There you can use the AUTOBUS- patch cables which are supplied with every technical interface, to make a fast connection from one interface to another (see picture below).
However, the wires in the patch cable only have 0.25mm² section so the length you can have is much smaller than on the standard AUTOBUS cable which is mentioned in the explanation above. We recommend, to connect up to ten technical interfaces per patch-cable network. If you have more then ten, you restart from the AUTOBUS cable and use another up to 10 patch connections. So you make a little star network with short patch network of max. 10 interfaces per net.
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