LS SERIES SERVICE MANUAL
ISSUE 4.0 MICROPROCESSOR CIRCUITS 3
The PWM signal controls both the speed and direction of the drive motor as shown below: -
PWM Signal Motor Control
1:1 mark/space ratio Machine stopped
< 1:1 mark/space ratio Machine running UP slowly
<< 1:1 mark/space ratio Machine running UP fast
> 1:1 mark/space ratio Machine running DOWN slowly
>> 1:1 mark/space ratio Machine running DOWN fast
The safe-line enable signal (SLEN) is normally Low and goes High to allow the user to
energise the safe-line. This signal is produced on pin 53 of the PLA, IC26, and is fed to the
Motor Drive PCB via pin 9 of the 26-way ribbon cable.
If the safe-line is open, i.e. the yellow lamp is still lit, the Motor Drive PCB will produce a low
level safe-line open (SLOPEN) signal and this is fed to pin 34 of the PLA, IC26, via pin 22 of
the 26-way ribbon cable. This low signal will prevent the machine from being driven and give
a "Safe-Line Open" message if the user tries to run the machine.
If the motor current rises excessively when the machine is running, the Motor Drive PCB will
produce a high level FAULT signal and this is fed to pin 39 of the PLA, IC26, via CN9 pin 17
of the 26-way ribbon cable. This high signal will stop the machine and give a "Motor Fault"
message.
2.5 Limit Switches
The limit switches are normally closed (N/C) microswitches mounted on the right hand side of
the lower casting. Either switch will open if the crosshead actuator arm moves the limit rod to
operate it.
One side of the lower limit switch is connected to pin 1 (Red wire) of CN2 on the Motor Drive
PCB and this is connected to pin 36 (Lower Limit) of the PLA, IC26, via pin 20 of the 26-way
ribbon cable. The other side of the lower limit switch is connected to pin 2 (Blue wire) of CN2
on the Motor Drive PCB and this is connected to 0V. The "Lower Limit" line can be pulled
high by a resistor in NR11 but is normally held low by the N/C lower limit microswitch. If the
lower limit switch is opened when the machine is driving downwards, the machine will stop
with a "Lower Limit" error message on the console.
One side of the upper limit switch is connected to pin 4 (Yellow wire) of CN2 on the Motor
Drive PCB and this is connected to pin 35 (Upper Limit) of the PLA, IC26, via pin 21 of the
26-way ribbon cable. The other side of the upper limit switch is connected to pin 3 (Blue
wire) of CN2 on the Motor Drive PCB and this is connected to 0V. The "Upper Limit" line can
be pulled high by a resistor in NR10 but is normally held low by the N/C upper limit
microswitch. If the upper limit switch is opened when the machine is driving upwards, the
machine will stop with an "Upper Limit" error message on the console.
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