Channel Lock When Undercarriage Is Retracted; Powerbus - PowerBox Systems Champion SRS Instruction Manual

The positional values vary according to your linkages, and must be adjusted to suit your individual model. Clearly
it is important to avoid your wheel doors jamming (striking their mechanical end-stops). The timing values shown
here should also be set to suit your requirements. The task numbering does not need to coincide with the timed
sequence; for example, Task 5 could be set to run before Task 2.
Our example clearly shows how the function is built up. Additional movements or intermediate stops when the
doors open or close can be added at any time; all you need is to set up a new free task. Viewed overall, there is
now no reason at all why the retraction and extension of the undercarriage in the model should not exactly emu-
late that of the full-size aircraft. In other words: you can give free rein to your imagination.
Note: if you wish simply to switch servos or valves on or off, you must always enter a time difference in the
sequence, as the door sequencer needs a small amount of time to carry out its calculations. The following is
an example for a retract valve:
The time lag of 0.1 s is sufficient, and is virtually unnoticeable in practice.
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UP » DOWN means undercarriage extension. Output
3 of the door sequencer has been selected. The servo
runs from its initial value of 1100µs (right servo end-
point) to the stop value of 1500µs (servo centre).
The servo only starts moving 1.0 seconds after the
switch is operated, and the period is 3.0 seconds (4.0
s - 1.0 s).
Task 1 has now completed its course.
After a pause lasting 2.0 seconds at servo centre, the
servo starts moving in the direction of 1800µs (left
servo end-point). The movement period is 2.0 se-
conds (8.0 s - 6.0 s).
Task 2 has completed its course.
DOWN » UP means undercarriage retraction. In this
example, when the switch is operated, the servo im-
mediately starts running slowly from the left to the
right servo end-point (Start time 0.0 s).
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Important: the first START POSITION at UP » DOWN must always coincide exactly with the last STOP PO-
SITION of DOWN » UP. This simply means that the last task must cause the servo to return to its starting
value, regardless of any individual intermediate steps you create! If the wheel door servos carry out unusual
or unexpected movements when you try out the programmed sequence, please check your tasks!

8. CHANNEL LOCK WHEN UNDERCARRIAGE IS RETRACTED

The PowerBox Champion SRS's door sequencer also features one last unique function: it is now possible to
switch a channel off when the undercarriage is retracted. The purpose of this feature is to prevent the retracted
nosewheel moving inside the fuselage when the pilot gives a rudder command, as this may cause the mecha-
nical system to jam. The function can be found under GEAR UP - OUTPUT OFF in the Door Sequencer menu.
Simply use the SensorSwitch to select the output which you wish to disable when the undercarriage is retracted.
Select the output, and confirm your choice with the SET button; at the same time the system stores the position
of the nosewheel servo at which it is to remain.
Caution: This function is extremely useful, but it also creates a danger: if you accidentally include a control
channel (e.g. elevator) in your programming, the control channel will then be switched off when you retract
the undercarriage after the model takes off. This will usually result in loss of the model!

9. POWERBUS

The PowerBUS is the key to a completely new servo wiring arrangement. The PowerBUS consists of three wires
which supply current and signal to the servos connected to the unit. 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 positional information for multiple servos is transferred in digital form. The information for indivi-
dual servos carries 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.
The advantage is perfectly obvious: all you need is one three-core lead in order to supply the essential informati-
on to several servos. The wiring is much simpler, and there is also a significant weight reduction.
However, until now there has always been one drawback: if a short-circuit occurs in one servo, this blocks the
bus lead, and all the servos connected to it stop working. Here at PowerBox-Systems we have now completely
eliminated this former disadvantage:
The servo distributors which we have developed are protected against short-circuits in the power supply wires
and the signal wire! This means that if one output is shorted out at a servo distributor, that output is switched off
within a few micro-seconds, and the bus lead remains active.
This supplementary feature is very important to flight safety, since a servo bus without it is not suitable for use
in valuable model aircraft!
Another important point relating to servo bus systems must be taken into account: the more servos connected
to the servo bus, the higher the current that flows, and the more severe the demands on the wiring system. The
PowerBUS system is Plug-n-Play: our range of products includes special leads of different lengths, fitted with
connectors encapsulated using the HotMelt process.
The PowerBUS system does not necessarily require bus-enabled servos. If you wish to use conventional PWM
servos with the PowerBUS, you can use a PowerBUS distributor which converts the digital bus signal into PWM
signals.
Three different types of distributor are available:
- Order No. 9200: PowerBUS to PWM Four-way distributor, integral BUS / PWM converter
- Order No. 9210: PowerBUS to BUS Four-way distributor for bus-enabled servos
- Order No. 9220: PowerBUS Splitter Splitter, for expanding one PowerBUS lead into two
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