SC750 User Manual

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Service Manual: SC750, SC800, SC 750 ST, SC800 ST

Form Number 56043150 Page 87

Here is how the circuit works for the actuator. The Main Machine Controller directly drives the brush head actuator mo-

tor. It applies system voltage across the two actuator motor wires to move the motor up. It reverses polarity to move the

motor down. Each posion switch receives a 5 volt feed through a resistor from the controller which returns back to bat-

tery negave on a common wire to connector J2 pin 2. The controller has “internal voltmeters” which monitor the signal

voltage of each switch circuit. When the switch is closed, the voltage signal is approximately 0 volts. When the switch is

open, the voltage is approximately 5 volts.

1. Deck up - Retracted Posion switch = 5v (Other two switches = 0v)

2. Normal Scrub mode - Middle Posion switch = 5v (Other two switches = 0v)

3. Extreme Scrub mode is not used on Cylindrical Deck

Note: The actuator “extended” posion switch circuit is unique because it is also used as a communicaon line between

the Main Machine Controller and the baery charger. The addion of the baery charger on the circuit drops the 5v that

is normally seen when the switch is open to approximately 3 volts. This is normal.

When the key is turned o, if the brush head is down, the Main Machine Controller will raise the brush head to the full

“up” posion. When the operator requests the scrub mode, the controller drives the actuator down unl it sees the

Middle Posion switch open (5v). When the operator turns o the scrub funcon, the controller drives the actuator mo-

tor up unl it sees the Retracted Posion switch open again (5v). If more than one posion switch is open (5v) at a me,

the controller does not know which one to believe. It realizes there must be a problem and will not move the actuator.

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Nilfisk SC750 Heavy-Duty Cleaning