ATU-HP Technical Instruction Manual
Page 6-7
Section 6 Theory of Operation
Issue 2.0
6.3.6.1.3
The
Ant_Current_Sample
is
provided by the antenna current probe (see
paragraph 6.3.5). This sample is applied to
the associated transmitter, via serial
connection, and is used to cause automatic
power adjustments to keep the antenna
current constant.
6.3.6.1.4
The
Temp Sensor
input,
representative of the ATU-HP’s
temperature, is provided by the temperature
probe (U3 of temp probe PWB A5). If the
temperature exceeds 60°C, the
microcontroller will activate digital outputs
that turn on fans B2 and B3. This signal is
also applied to the associated transmitter
via serial connection.
6.3.6.2 Digital Inputs
8-bit shift registers U3 and U11 and their
associated components perform the
conditioning required to process digital
inputs. The digital inputs include nine push-
button switches for ATU control/setup, four
limit switches to protect the two servos from
reaching their end limits and two inputs to
monitor the fan speed. A clock input is
applied to microcontroller U8 at pin 10.
When U8 pin 9 is cleared and then set, the
current digital inputs are loaded into U3 and
U11. Data is shifted from U3-9 to U11-10,
and then from U11-9 to U8-11. All switch
inputs are momentary.
6.3.6.2.1
The nine switches that affect data
sent to the microcontroller are:
INCREASE
R
(S5),
DECREASE R
(S6),
INCREASE L
(S1),
DECREASE L
(S2),
INHIBIT R
TUNING
(S7),
INHIBIT L TUNING
(S3),
XMTR ON/OFF
(S8),
LOCAL/REMOTE
(S4) and
TUNE SETUP
(S9). Only the
LOCAL/REMOTE
switch will operate if the
ATU-HP is in remote mode.
6.3.6.2.2
The
INCREASE R
, and
DECREASE R
switches control the resistive
matcher movement and when pressed
activate the resistive matcher motor and
inhibit the
Voltage_Sample
and
Current_Sample
inputs from affecting the
resistive tuning.
6.3.6.2.3
The
INCREASE L
and
DECREASE L
switches control the
inductive motor movement and activate the
inductive tuning motor and inhibit the
Inc_L
and
Dec_L
microcontroller inputs from
affecting the inductive tuning.
6.3.6.2.4 INHIBIT R TUNING
and
INHIBIT
L TUNING
switches disable the ATU-HP
from auto tuning. Once the switch is
pressed the auto tune (for whichever motor
is inhibited) will not function until the switch
is pressed again.
6.3.6.2.5 LOCAL/REMOTE
switch toggles
from local to remote mode. In remote mode
all other switches are inactive.
6.3.6.2.6 XMTR ON/OFF
enables the user
to control a Vector series DGPS or NDB
transmitter from the ATU. The
microcontroller applies on/off commands to
the transmitter via serial connection.
6.3.6.2.7
The
TUNE SETUP
switch is used
during initial ATU-HP tuning when the
resistive matcher is not yet in circuit. Since
the resistive matcher (1/4-wave
transformer) is not in circuit, the
Inc_L
and
Dec_L
signals are read in reverse by the
microcontroller while in
TUNE SETUP
mode. For example: If
Inc_L
is high, the
DECREASE L
status LED will be on and
the inductive motor will turn correctly.
6.3.6.2.8
Four limit inputs (
R Limit Max
,
R
Limit Min
,
L Limit Max
and
L Limit Min
)
instruct the microcontroller if a tuning limit
has been reached and, regardless of tuning
signals or local switch settings, the motor will
not travel beyond the limit.
6.3.6.2.9
Two digital inputs (
Fan 1 Count
and
Fan 2 Count
) monitor fan rotation. With
each rotation of cooling fan B2’s (fan 1)
blade, the falling edge of the pulse at U8-32
will trigger an interrupt, effectively counting
the rotations. Resistor R114 and capacitor
C50 low-pass filter the input. Similarly, with
each rotation of cooling fan B3’s (fan 2)
blade, the falling edge of the pulse at U8-1
will trigger an interrupt, effectively counting
the rotations. Resistor R116 and capacitor
C51 low-pass filter the input.
