Filter
Top Products
AX3500 Motor Controller User’s Manual 81
Voltage Levels, Thresholds and Limit Switches
Using the PC utility, it is possible to exercise the motors and view the encoder readings.
See “Encoder Testing and Setting Using the PC Utility” on page 87.
If the Encoder counts backwards when the motor moves forward, correct this by either:
1- Swapping Channel A and Channel B on the encoder connector. This will cause the
encoder module to reverse the count direction, or
2- Swapping the leads on the motor. This will cause the motor to rotate in the opposite
direction.
Voltage Levels, Thresholds and Limit Switches
The encoder module’s input uses a comparator to reshape the encoder’s output signal. If
the signal is below a fixed 2.5V threshold level, then it is considered to be 0. If above, it is
considered to be 1. The output of this comparator feeds the quadrature detector and
counters.
Another set of comparators on the same input signals detects pulses that are above and
below a fixed 0.5V threshold. Using a special circuitry for creating multi-level signaling (see
next section below), the output of these comparators serves to detect the status of
optional limit switches.
Figure 52 and Figure 51 show the conditioned signals as seen by the encoder.
In Figure 52, the encoders are connected directly to the Channel A and B inputs. In this
case, it will cause a Switch Detection condition because the encoder’s 0 level is below
0.5V, which should be ignored.
In Figure 51, the encoder and switches are wired to the encoder module using a set of
resistors designed to create a multi-level signal combining both pieces of information.
Details on the necessary wiring is provided in the next section.
Since the encoder output signal is “shifted-up” by a few volts, it always stays above the
Limit Switch comparator’s threshold, and no Switch Detection condition is generated.
However, since the limit switches connect to ground when On, the level will dip below the
0.5V and generate a Switch Detection condition.
2.5V
0.5V
Signal on Channel A or B
Quadrature Signal
Switch Detect Signal
(Not meaningful)
FIGURE 51. Signals seen by encoder using direct connection and no limit switches