RoboteQ AX2850 - Manual (Page 68)

Connecting Sensors and Actuators to Input/Outputs
68 AX2550 Motor Controller User’s Manual Version 1.9b. June 1, 2007
Internal Voltage Monitoring Sensors
The AX2550 incorporates voltage sensors that monitor the Main Battery voltage and the
Internal 12V supply. This information is used by the controller to protect it against overvolt-
age and undervoltage conditions (see “Overvoltage Protection” on page 38 and “Under-
voltage Protection” on page 38). These voltages can also be read from the RS232 serial
port using the ?e query.
The returned value are numbers ranging from 0 to 255. To convert these numbers into a
Voltage figure, the following formulas must be used:
Measured Main Battery Volts = 55 * Read Value / 256
Measured Internal Volts = 28.5 * Read Value / 256
Internal Heatsink Temperature Sensors
The AX2550 includes temperature sensors making contact with the each of the two Heat-
sink sides of the controller.
These sensors are used to automatically reduce the maximum Amps that the controller
can deliver as it overheats. However, the temperature can be read using the RS232 port
using the ?m query, or during data logging (see “Analog and R/C Modes Data Logging
String Format” on page 166)
The analog value that is reported will range from 0 (warmest) to 255 (coldest). Because of
the non-linear characteristics of NTC thermistors, the conversion from measured value to
temperature must be done using the correction curve below.
It should be noted that the temperature is measured inside the controller and that it may
be temporarily be different than the temperature measured outside the case.
47kOhm
10kOhm
47kOhm
+5V 14
Ground 5
A/D
Ana 1: 11
Ana 2: 10
Ana 3: 12
Ana 4: 8
FIGURE 38. AX2550 Analog Input equivalent circuit