CHAPTER 2. INSTALLATION 25
RC9 Ramped Clock
Limit Switch
Connections
The limit interlock circuits are brought into operation by shorting the
appropriate limit input to 0V. This method of connection is shown in
Figure 2-9(a) and is satisfactory when small microswitches,
reedswitches or proximity switches are used. However, if industrial
machine-tool type switches are used the current drawn by the limit
input may be insufficient to ensure good contact wetting and the
operation may be unreliable. In this case a preferred connection
arrangement is shown in Figure 2-9(b) in which a normally-closed
contact is used in conjunction with a pull-down resistor. This
configuration is virtually fail-safe since the limit circuit is activated by
the switch contacts becoming open-circuit.
LIMIT
INPUT
0V
LIMIT
SWITCH
(NO)
(NC)
SWITCH
LIMIT
0V
INPUT
LIMIT
1K OHMS
1 WATT
(a)
(b)
+24V
Figure 2-9. Limit Switch Configurations
RC9 Ramped Clock:
Setting Up
The most suitable method of setting up the Ramped Clock will
depend on the application. If defined stepping rates are required and
it is known that these are well within the capability of the motor, the
adjustments may be made using a suitable counter or frequency
meter. If on the other hand the system is required to move to a new
position in the shortest possible time the adjustments should be
made experimentally on the complete system. In either case it will
normally be necessary to set up the acceleration and deceleration
rates experimentally. If wide variations of load are expected, the
adjustments should be checked at both maximum and minimum
load. This is necessary because a large frictional load aids
deceleration and a permissible deceleration rate at full load may be
unacceptable when the load is reduced.
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