Installation manual

Danaher Motion Kollmorgen 08/04 Appendix B
SERVOSTAR S Installation M-SS-001-01 Rev. T 107
Another common sense approach is to use differential transmission
for the signals to provide the highest degree of noise immunity.
Differential line drivers are required by the SERVO
STAR. The
differential line signals follow the RS-485 format where pulses are
sent up and down a 120 Ω cable. Termination is expected at both
ends and the SERVO
STAR provides the required termination.
Deviations from a 120 Ω characteristic impedance cable when
using long cables can result in poor performance.
B.1.8 DESIGN CONSIDERATIONS
The SERVOSTAR has a maximum frequency input for
incremental encoders of 2.5 MHz. This cannot be exceeded
under any circumstance.
Encoders consume 5 V. The 5 V is typically regulated inside
the drive through a cable to the encoder. Tolerances on the
5 V must be considered for IR loss within the cable. An 18
AWG conductor pair providing the 5 V at a 250 mA drive
result in approximately ¼ V drop and become the limits from
the encoder's 5 V rating perspective. Consideration of cable
length 5 V current draw is extremely important for good
system design. The SERVOSTAR's encoder supply is 5 V ±
2% with 250 mA maximum draw.
When using incremental encoders, the SERVOSTAR
receives the encoder pulses, buffers them electrically and
then outputs them to the encoder equivalent output port. The
phase delay in the transport of these signals is extremely
small. Be sure to run all encoder cables in conduit or wire
tray that is free from wires carrying or emitting electrical
noises such as solenoid wires and armature cables.
B.1.9 REFERENCE VARIABLES
For additional information on any of these commands, refer
to the SERVOSTAR
®
CD VarCom Manual.
ENCINIT - This command triggers the encoder initialization
process.
ENCINITST - This variable may be queried and returns
status of the initialization process. This variable
assumes one of three values:
0 = The initialization process has not started.
1 = The initialization process is in progress.
2 = The index position has been determined and the
initialization process is complete. The flag is reset to
zero when you manually set the index position.