Service manual

Electrical Service Manual V4.0
6
6-2
CENTRAL COMMAND II
CONTROLLER OVERVIEW
The controller used in the Central Command II system is manufactured by P&G drives and
is much more than a standard speed controller. The controllers heart is an industrial micro
computer. The P&G series of controllers used in the Central Command II is the “Trio” series
that was designed primarily for the commercial and industrial cleaning equipment segment.
This controller has the capability to run on 24 or 36 volts DC so the same controller works
across nearly our entire product line.
CONTROLLER OPERATION
The controller operation is unlike previous control systems on our machines and differs in a
number of ways. The first of these differences is the lack of battery voltage on most of our
control switches. The majority of switches on the control panel are now used to send very
low voltage signals to and from the computer. They must be diagnosed in a special way or
the controller may be permanently damaged. There are no longer separate circuit breakers
or contactors for each device; the circuit switching and protection is handled by the control-
ler. The control panel switches are no longer connected directly to a solenoid that turns on
a component, they are connected to the input circuits of the controller and send a signal to
the controller and then the controller turns on the component based on certain criteria set
by the controllers parameters.
INPUTS
The switches in the Central Command II System receive reference voltages from the con-
troller and then send these signals, in the form of low or high reference voltages, to the
controller. The controller interprets these signals and then the program inside the controller
decides what device output is being requested and how it should operate the output.
TRI-STATE LOGIC
The Central Command II system uses very low voltage throughout its control system, this is
called tri-state logic. The voltages used are less than battery voltage and the controller will
be destroyed if battery voltage is introduced into the control circuits. The tri-state logic uses
3 voltages as follows;
LOW = 0.0 - 0.3 volts
MID = 0.8 - 2.7 volts
HIGH = 4.8 - 5.2 volts
The low and high voltages are reference voltages created by the controller. These voltages
are sent to the various controller inputs via the control panel switches. The controller then
makes the machine operate a certain way based on the input voltage. All inputs at the
controller, with the exception of the throttle input, are at a voltage of 0.8 to 2.6 volts when
they are at a “MID” or un-switched state. When a signal is sent to an input via a switch it is
either a “LOW” or “HIGH” reference signal. The computer monitors the input terminal many
times a second and when the voltage of it changes, the computer reacts accordingly to the
program turning the outputs of the controller on or off. The P&G controller has two types of
inputs, ON/OFF and Varied Voltage.