RoboteQ AX2550/2850 user manual Using the Analog Inputs to Monitor External Voltages, Ntc

Connecting Sensors and Actuators to Input/Outputs

10kOhm

10kOhm

NTC

Thermistor

+5V 14

Input Ana 1 11 or Ana 2 10

Ground 5

AX2500 Internal Resistors and Converter

47kOhm

A/D 10kOhm

47kOhm

FIGURE 31. NTC Thermistor wiring diagram

Thermistor are non-linear devices. Using the circuit described on Figure 31, the controller will read the following values (represented in signed binary) according to the temperature.

	100
	50
Input Reading	0
Analog	-50
	-100
	-150
	-20	-10	0	10	20	30	40	50	60	70	80	90	100	110
						Temperature in Degrees C

FIGURE 32. Signed binary reading by controller vs. NTC temperature

To read the temperature, use the ?p command to have the controller return the A/D con- verter’s value. The value is a signed 8-bit hexadecimal value. Use the chart data to convert the raw reading into a temperature value.

Using the Analog Inputs to Monitor External Voltages

The analog inputs may also be used to monitor the battery level or any other DC voltage. In this mode, the controller does not use the voltage information but merely makes it avail- able to the host microcomputer via the RS232 port. The recommended schematic is shown in Figure 33.

60 AX2500/2850 Motor Controller User’s Manual Version 1.7. February 1, 2005