Motors - Planmeca Proline XC Technical Manual

Chapter I - FUNCTIONAL DESCRIPTION

2.3 Motors

There are six motors in the equipment that perform all the movements needed. In the follow-
ing is explained where the motors are, what they do, where they get their driving power from
and what is the system how they are operated.
Five of the motors are stepper motors the operating method of which is different from the DC-
motor. They have two coils with two wires to each and the current is flowing through the coils
in both directions in turn with a phase difference that causes the rotation. Now, if the stepper
motor is wrongly connected or one or two wires are broken the motor might run not at all, run
with low torque, run to wrong direction, change the rotation direction by itself or run at double
or half speeds. To check this the coil resistances should be about 5 ohms each and one coil
connected to connector pins 1 and 2 and the other to pins 3 and 4. If it runs to wrong direction
just reverse one coil polarity. Reversing both causes nothing. Measuring the voltages needs
an oscilloscope because the motors are driven by about 40 kHz switch mode current regu-
lated power supplies. Best to have a reference motor with or to cross connect two motors to
check the driver circuit operations. If cross connecting, remember that the limit sensors oper-
ate wrongly.
Up/down motor
The up/down motor is located on the top of the column. It's function can clearly be seen, it is
moving the actual X-ray part in vertical direction along the column. It is a DC brush motor with
a worm gear of 1:72 and it gets it's drive from the keyboard processor first downwards along
the spiral cable (on the left side seen from the front) and then upwards along a cable located
inside the column.
When this motor is activated, it is first driven one second slowly and then accelerated softly to
full speed. When the button is released the motor stops immediately if it was still in the slow
mode, but slows down softly if it was running faster. If the motor is driven to the end of it's
traverse path (limit sensor) the system performs a quick stop by using the motor as a brake
(short circuit). The motor speed is controlled with pulse width control at 200 Hz frequency,
that can be heard as a humming sound.
The slow speed can be adjusted independently to both directions to fulfill all needs.
When the motor is driven to the limit sensor and stopped, it will not start to that direction but
only to the other. When started to the other direction it will run slowly as long as it gets back to
the sensor and over it. To avoid hazards the system will speed up the motor if it doesn't reach
the sensor within 5 seconds when the button is kept pressed, that normally is long enough,
and ignore the sensor pulse. Therefore it should be noted that if for some reason the up/down
movement is driven over the limit sensor and cannot be driven back within this time (jammed)
the button should not be operated more than 4 seconds at a time while helping the motor by
hand. If this is not taken care of, the system detects the sensor as if it was the sensor of the
other end and never comes to the normal operating range.
In this case enter the slow speed adjustment mode to the direction you want to go and press
the button. This mode ignores the sensor and enables you to reach the normal range
between sensors. While in the normal range exit the adjust mode and then drive the motor to
the other end sensor to get it operative again.
Layer adjust motor
This motor is located at the layer adjust mechanism in the lower fixed part. It's function is to
move the bite block, temple rests and handles (and the patient) horizontally in order to get the
patient's teeth in the right position relative to the layer positioning light. It is a stepper motor
and it gets it's drive from the keyboard processor.
When this motor is activated, it will first drive one second at a slower speed and then acceler-
ate to the full speed.
I-14 Planmeca Proline XC X-ray unit
ELECTRICAL PARTS AND THEIR FUNCTIONS
Technical Manual