User Manual

Table Of Contents
Connecting External Thermistor to Analog Inputs
Advanced Digital Motor Controller User Manual 53
Important Warning
The tachometer’s polarity must be such that a positive voltage is generated to the
controller’s input when the motor is rotating in the forward direction. If the polarity
is inverted, this will cause the motor to run away to the maximum speed as soon
as the controller is powered and eventually trigger the closed loop error and stop.
If this protection is disabled, there will be no way of stopping it other than pressing
the emergency stop button or disconnecting the power.
Connecting External Thermistor to Analog Inputs
Using external thermistors, the controller can be made to supervise the motors tempera-
ture and cut the power output in case of overheating. Connecting thermistors is done ac-
cording to the diagram shown in Figure 3-12. Use a 10kOhm Negative Coefficient Therm-
istor (NTC) with the temperature/resistance characteristics shown in the table below.
Recommended part is Vishay NTCALUG03A103GC, Digikey item BC2381-ND.
TABLE 3-1. Recommended NTC characteristics
Temp (˚C) -25 0 25 50 75 100
Resistance (kOhm) 129 32.5 10.00 3.60 1.48 0.67
33kOhm
20kOhm
Internal Resistors
and Converter
+5V
Ground
A/D
10kOhm
10kOhm
NTC
Thermistor
FIGURE 3-12. NTC Thermistor wiring diagram
Thermistors are non-linear devices. Using the circuit described in Figure 12, the controller
will read the following values according to the temperature. For best precision, the analog
input must be configured to read in Relative Mode.
The analog input must be configured so that the minimum range voltage matches the
desired temperature and that action be triggered when that limit is reached. For example
500mV for 80oC, according to the table. The action can be any of the actions in the list. An
emergency or safety stop (i.e. stop power until the operator moves command to 0) would
be a typical action to trigger.