Operation; Control Circuit Components - nifty 170SD series Operating/Safety Instructions Manual

4.

Operation

4.1

CONTROL CIRCUIT COMPONENTS

4.1.1
CONTROL BOARD: - Situated under the canopy, the encapsulated control board comprises of a
PCB (printed circuit board) design which incorporates all of the relays to control the machine
operation. The control board is common to all models and contains functions which might not be
utilised on your machine. A thermal trip switch is integral to the box, which protects the control
circuit components. If power is lost, the switch can be manually reset.
4.1.2
TILT ALARM: - Fitted to the top of the control board box, the tilt alarm is a solid state sensor which
monitors the inclination of the machine. It directly controls the BRV (Brake Release Valve) and if the
machine had been set up on an excessive incline would sound the alarm. Platform operation is
unaffected, allowing the operator to stow the machine. This then restores the drive and it is then
possible to drive back onto level ground, fully restoring machine operation. The tilt alarm does not
operate when the machine is being driven, as the boom switch overrides this function as long as
the booms are lowered.
4.1.3
SOUNDER: - Situated beneath the PCB is a small electric sounder, which is used to provide an
intermittent alarm whenever the machine is in operation. Pushing a green "power control" button or
depressing the foot switch in the cage (if fitted) will energise this sounder. This serves to warn
personnel of the operation of the machine.
4.1.4
KLAXON: - Also mounted on the top of the control board box is a klaxon, which performs several
functions.-
Firstly, it can be used as a manual alert, by pushing the "Horn" button at the Platform Control
Station.
Secondly, it is the device which sounds continuously if the tilt alarm sensor detects excessive
inclination, with the booms raised.
Lastly, it is linked into the battery management system, such that when low battery state is reached
the "pulsing" of the DC motors is mimicked by the Klaxon, re-enforcing the message to the operator
to re-charge the batteries.
4.1.5
DRIVE CONTROL VALVE (DCV):- The motion control valve comprises of several individual
components all directly involved in the hydraulic supply to the wheel drive motors. Principal
amongst these are the drive control valves, which electrically change the drive motor hydraulic
supply from series flow to parallel, or vice versa. This control function is only available when the
booms are lowered and allows the operator to select "Hi" or "Lo" drive. "Hi" drive gives fast speed
of travel, but low gradeability, "Lo" drive gives best gradeability, but slow speed. "Lo" drive is used
for climbing inclines and delicate positioning of the machine.
4.1.6
BRAKE RELEASE VALVE (BRV):- The motion control valve also incorporates a solenoid operated
dump valve which controls the brake function on the machine. This valve must be energised to
allow the machine to move. If no voltage is present, the wheel motors will not be able to develop
drive torque, whilst at the same time, the spring applied parking brakes will remain engaged. Only
when the green "power control" button is being used (or the platform foot switch is depressed) will
the BRV operate. If the tilt alarm sensor detects an excessive inclination whilst the booms are
raised, it is the BRV which is de-energised to isolate the machine (at the same time the Klaxon tone
changes to a continuous one to indicate this condition).
English/USA 09/03
Operating & Safety Instructions
SD Series
21