RoboteQ AX3500 Important Warning, Connecting Sensors and Actuators to Input/Outputs, Ana 1 p11

Connecting Sensors and Actuators to Input/Outputs

Since the controller only accepts a 0 to 5V positive voltage as its input, the circuit shown in Figure 33 must be used between the controller and the tachometer: a 10kOhm potentiom- eter is used to scale the tachometer output voltage to -2.5V (max reverse speed) and +2.5V (max forward speed). The two 1kOhm resistors form a voltage divider that sets the idle voltage at mid-point (2.5V), which is interpreted as the zero position by the controller. The voltage divider resistors should be of 1% tolerance or better. To precisely adjust the 2.5V midpoint value it is recommended to add a 100 ohm trimmer on the voltage divider.

With this circuitry, the controller will see 2.5V at its input when the tachometer is stopped, 0V when running in full reverse, and +5V in full forward.

1kOhm

Zero Adjust 100 Ohm pot

1kOhm

	+5V 14
Max Speed Adjust	Ana 1: 11
10kOhm pot
	Ana 2: 10
	Ana 3: 12
Tach	Ana 4: 8

Ground 5

Internal Resistors and Converter

47kOhm

A/D 10kOhm

47kOhm

FIGURE 33. Tachometer wiring diagram

The tachometers can generate voltages in excess of 2.5 volts at full speed. It is important, therefore, to set the potentiometer to the minimum value (cursor all the way down per this drawing) during the first installation.

Since in closed loop control the measured speed is the basis for the controller’s power out- put (i.e. deliver more power if slower than desired speed, less if higher), an adjustment and calibration phase is necessary. This procedure is described in “Closed Loop Speed Mode” on page 101.

TABLE 12. Analog Speed Sensor connection depending on operating mode

Operating Mode	Ana 1 (p11)	Ana2 (p10)	Ana 3 (p12)	Ana 4 (p8)
RC or RS232 - Dual Channel	Speed 1	Speed 2	Unused	Unused
Analog - Dual Channel	Command 1	Command 2	Speed 1	Speed 2
RC or RS232 - Single Channel	Speed	Unused	Unused	Unused
RC or RS232 - Dual Channel	Command	Unused	Speed	Unused

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 with no way of stopping it other than pressing the emer- gency stop button or disconnecting the power.

64 AX3500 Motor Controller User’s Manual Version 1.9b. June 1, 2007