Service manual

Electrical Service Manual V4.0

6-4

CENTRAL COMMAND II

CONTINUITY TESTS

The controller in our Central Command II system has onboard testing capabilities that test

the ﬁtness of different circuits on the machine. These circuits are the Drive Motor, Brush Mo-

tor, Vacuum Motor and Parking Brake. To do this the controller sends out voltage on one of

the output terminals for a circuit and watches to assure the voltage is returned on the other

terminal of the output circuit. If the controller does not see the voltage sent out one terminal

return to the other is calculates that their is a fault in the circuit it is testing and displays an

error code on the LCD display on the control panel. Depending on which circuit it is analyz-

ing, a detected fault can disable the machine until the fault is corrected. The current sent

out to test these circuits is extremely low and is not enough to run any of these components

but it is enough current for you to see the voltage on your volt meter when testing. For this

reason, for an output to be considered turned “On” by the controller you would have to see

within 1 volt of battery voltage coming out of the output.

PULSE WIDTH MODULATION

The P&G Controller used in our Central Command II machines uses a technology called

Pulse Width Modulation (PWM). PWM controls a circuit by switching the power on and off

to it many times a second. By switching the voltage to the circuit on and off many times a

second the controller operates efﬁciency by not wasting electricity by lowering the voltage

through resistance. By using PWM we are able to control how an output circuit starts and

stops, as well as to control the speed that a device runs at when a motor is being controlled.

SOFT START

When a output circuit is powered with PWM we are able to “Soft Start” a motor, meaning we

start the motor gently and then increase its speed over a duration of 1 second. This meth-

od of controlling a motor is much gentler and greatly extends motor life as well as all the

componentry that may be driven by the motor, such as drive shafts or chains. Three of the

outputs; traction, brush & vacuum, have a soft start function on them. This function provides

the ability to start and stop a motor gradually over a measured period of time, 0-10 seconds.

This aids in the longevity of the motors and anything driven by them as it greatly decreases

the shock load on them. The soft start settings are changed through the controller program-

ming.

DOWN PRESSURE CONTROL

The down pressure of the scrub deck is monitored and maintained by the controller. It is

adjusted many times a second to deliver consistent brush pressure with changing ﬂoor

conditions. The controller monitors the amp draw of the scrub motors which increases and

decreases with brush deck pressure and ﬂoor surface change. The amp draw has a target

value and the controller works to keep the motors at the selected amp draw by increasing

or decreasing brush pressure. The target pressure is represented on the LCD display and

changed using the brush pressure switch on the control panel.