TruTrak DFC Install Manual - Manual (Page 5)

Electrical Wiring
All TruTrak DFC series (DFC-200, DFC-200AS, DFC-250, DFC-250AS, DFC-300, DFC-300AS) autopilots have consistent
wiring requirements. Therefore, this manual covers all such units, with special notations covering any differences between the
units. The DFC-200 programmer is mechanically identical to the DFC-250 and differs only in its internal circuitry and
software. The DFC-300 autopilot system consists of a DFC-250 programmer and a YD-300 yaw damper module, together with
the three servos that constitute the system.
The table below provides a brief explanation of each pin function on the main 37-pin connector P101.
P101 Autopilot Rear Connector (Viewed from rear of autopilot)
P101
Pin
Function Notes
1 Dedicated ground connection for Pitch Reverse Jumper.
Pitch Reverse Jumper,
present or absent, as follows: Direction of servo arm / capstan rotation
(as viewed from face of the servo body)
for UP elevator
Pin 2 open (no connect): Servo CCW (counter-clockwise) Î UP
2
Pin 2 Jumpered to pin 1: Servo CW (clockwise) Î UP
See note 4 on wiring
diagram
3 Auxiliary RS-232 Output. Presently unused, intended for future expansion.
4 LAMP1 (see also pin 18) A source of variable DC from external dimming source. Drives the
LCD backlighting circuit and six 60 mA lamps. If left disconnected, backlight will be full-on
and buttons will be unlighted. Draws approximately 500 mA at 12v, 250 mA at 28v.
Dimmer is wired
based on supply
voltage. See note 2
on wiring diagram
5 Yaw Damper Gyro Gain. A signal from the autopilot which sets the amount of response the
yaw damper exhibits to azimuth disturbances.
DFC-300 only
6 Yaw Damper Tilt Gain. A signal from the autopilot which sets the amount of response the
yaw damper exibits to a given amount of deflection of the “ball”.
DFC-300 only
7 No Connection. Reserved for future expansion.
8 Yaw Damper Activate. A signal from the autopilot which turns on the yaw damper function. DFC-300 only
9 Analog DG/HSI Input. A zero to 5V DC signal centered at 2.5 volts from an external steering
device. An adapter specific to a given DG or HSI is required. Consult factory for details on this
adapter.
10 Pitch Servo Torque Control. A signal from the autopilot to the pitch servo which sets the
amount of torque to be delivered by the servo.
11 Pitch Servo Trim Sensor. A signal from the pitch servo to the autopilot which indicates an
out-of-trim condition and its direction.
12 Autopilot Master (+12 to +28 V DC). The autopilot itself draws less than ½ ampere. Most of
the current required by the autopilot system is used by the servos (up to 1A per servo).
13 Audio alerter signal. This pin may be wired to an unswitched input of an audio panel. The
autopilot uses various tones to denote specific events (loss of GPSS, capture Glideslope, etc).
Volume is adjustable within a setup screen of the autopilot.
14
15
16
17 Pitch Servo control lines. These lines cause the stepping motor in the pitch servo to run in the
appropriate direction at the desired velocity. They are small-signal lines and do not have any
substantial current-carrying capability or require any special shielding. Connect to pitch servo
as shown on wiring diagram. Do not attempt to
reverse servo
direction by
swapping wires
18 LAMP2 (see explanation for pin 4, above).
19 Ground Connection. Provide #20 AWG to common grounding point.
20 Control Wheel Switch. Connect as shown in wiring diagram to a SPST momentary switch
located remotely to the autopilot for convenient engage/disengage function.
21 CDI LEFT
22 CDI RIGHT Analog +/- 150 mV differential signals from Nav receiver. Pin 22 more
positive than pin 21 indicates CDI needle right-of-center.
TruTrak Flight Systems DFC Autopilot Installation Manual
3 May 2006 Printing