Description
PowerBus Lead 90cm (35.4in) with “hot-melt” MPX connectors.
PowerBus™ cable is manufactured specially for PowerBox Systems. The PowerBus™ cable is extremely flexible, and is made up using very thin individual strands in order to pass the maximum current through the given cross-sectional area of 1.5 mm². The in-sulation is made of a special material which is also employed in full-size aviation. It is virtually indestructible, and offers excellent protection even when reduced to just a thin
film around the copper conductor. This insulation produces a weight reduction of about 30% compared with the much cheaper PVC. The insulation is fire resistant, and its heat resistance is much higher than the usual PVC.
To save more weight, the conductors are of different thickness: power is carried by two thick wires (1.5 mm²), while a thin wire of 0.25 mm² is used for the signal. This produces a further weight saving of 27%.
The PowerBus is the basis of a completely new method of wiring servos. The PowerBus consists of a three-core cable which supplies current and signal to the servos connected to it. At first glance this is nothing unusual, but the big difference lies in the signal wire. When conventional servo signals are transferred, the signal wire always carries the information for one individual servo only – this is a PWM (Pulse Width Modulated) signal. In a servo bus system the signal wire carries positional information for multiple servos in digital form. The information for individual servos includes address data, and since each servo is assigned its own individual address, it can read out “its” information from the data stream, and convert it into a movement of the control surface. PowerBus to PWM adapters can also be employed to enable the use of servos without their own decoder; in this case the adapter carries out the decoding.
The advantage of this arrangement is obvious: all you need is one three-core lead in order to supply the essential information to several servos. The wiring is much simpler, and there is also a significant weight saving.
However, until now there has always been one disadvantage to bus systems: a short-circuit in one servo causes the bus lead to be blocked, and all the servos connected to it stop working. Here at PowerBox Systems we have completely eliminated this former drawback:
The servo distributors which we have developed are protected against short-circuits in the power supply lines and the signal line! This means that, if one output is shorted out at a servo distributor, within a few micro-seconds that output is switched off, and the bus lead remains active.
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