Design And Function - Husqvarna Automower 420 Technical Manual

5.1 Design and function

5.1.1 Chassis and body
The robotic lawnmower is structured mechanically
around the following major components:
• Body
• Top cover (450X)
• Display cover
• Chassis, upper section
• Chassis, lower section
There are 2 sealing strips, one between the upper
and lower sections of the chassis, plus one between
the upper section of the chassis and the display cov-
er. It is important to replace these sealing strips each
time the mower is opened.
5.1.2 Circuit boards
There are up to eight circuit boards in the robotic
lawnmower:
• Main circuit board (1)
• HMI board (2)
• Automower Connect module (450X) or
GPS-module (430X) (3)
• Front loop sensor circuit board (4)
• Lift sensor circuit board (2 of) (5)
• Collision sensor circuit board (2 of) (6)
• Cutting height sensor circuit board (7)
• Ultrasonic board (450X only) (8)
The circuit boards contain the electronics and soft-
ware required to control the mower's functions. In
simple terms this can be described as the main
circuit board gathering sensor signals that are evalu-
ated by the software and generating control signals
for the motors. The HMI circuit board collects its in-
formation from keys that are pressed on the keypad
and conveys the menu selections that the user has
made to the main circuit board, which saves them in
its memory. These selections subsequently become
the conditions for the main circuit board to take into
account in evaluating the sensor signals. The HMI
circuit board also has the task of presenting informa-
tion from the main circuit board to the display.
The main circuit board and the HMI circuit board
contain their own separate software. If any of these
boards are replaced, they have to be programmed
via Autocheck EXP.
A new HMI circuit board contains software but, after
being fitted, it must always be programmed to be up-
dated to latest version.
The other circuit boards do not have any software,
and consequently do not need to be programmed
after a replacement.
5. REPAIR INSTRUCTIONS
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8
5
1
3
4
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