Connecting User Devices to Analog Inputs

To Battery +Terminal

47kOhm

4.7kOhm

+5V 14

10 or 11

Ground 5

AX2500 Internal Resistors and Converter

47kOhm

A/D 10kOhm

47kOhm

FIGURE 33. Battery voltage monitoring circuit

Using these resistor values, it is possible to measure a voltage ranging from -5V to +60V with a 0.25V resolution. The formula for converting the A/D reading into a voltage value is as follows.

Measured volts = ((controller reading + 128) * 0.255) -5

Note: The A/D converter’s reading is returned by the ?p command and is a signed 8-bit hexadecimal value. You must add 128 to bring its range from -127/+127 to 0/255.

Connecting User Devices to Analog Inputs

The two analog inputs can be used for any other purpose. The equivalent circuit for each input is shown in Figure 34. The converter operates with an 8-bit resolution, reporting a value of 0 at 0V and 255 at +5V. Care should be taken that the input voltage is always posi- tive and does not exceed 5V. The converter’s intrinsic diodes will clip any negative voltage or voltage above 5V, thus providing limited protection. The value of the analog inputs can be read through the controller’s RS232 port.

+5V 14

 

Input Ana 1 11

47kOhm

or Ana 2 10

A/D

 

 

10kOhm

 

47kOhm

Ground 5

FIGURE 34. AX2500/2850 Analog Input equivalent circuit

AX2500/2850 Motor Controller User’s Manual

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RoboteQ AX2550/2850 user manual Connecting User Devices to Analog Inputs, Measured volts = controller reading + 128 * 0.255