RoboteQ AX2550/2850 user manual Potentiometer wiring, Using Optical Encoders in Position Mode

Potentiometer wiring

The mechanical coupling between the motor and the sensor must be as tight as possible. If the gear box is loose, the positioning will not be accurate and will be unstable, potentially causing the motor to oscillate.

Some sensor, such as potentiometers, have a limited rotation range of typically 270 degrees (3/4 of a turn), which will in turn limit the mechanical motion of the motor/potenti- ometer assembly. You may consider using a multi-turn potentiometer as long as it is mounted in a manner that will allow it to turn throughout much of its range, when the mechanical assembly travels from the minimum to maximum position.

Important Notice:

Potentiometers are mechanical devices subject to wear. Use better quality potenti- ometers and make sure that they are protected from the elements. Consider using a solid state hall position sensor in the most critical applications. Optical encoders may also be used when operated as discussed in “Using the Encoder to Measure Speed” on page 139.

Potentiometer wiring

When using a potentiometer, it must be wired so that it creates a voltage that is propor- tional to its angular position: 0V at one extreme, +5V at the other. A 10K potentiometer value is recommended for this use.

Connecting the potentiometer to the controller is as simple as shown in the diagram on Figure 70.

+5V 14

Input Pos 1 11 or Pos 2 10

10kOhm

Ground 5

FIGURE 70. Potentiometer wiring in Position mode

AX2500 Internal Resistors and Converter

47kOhm

A/D 10kOhm

47kOhm

Using Optical Encoders in Position Mode

Optical Encoders require special handling. See Figure 12, “Installing, Connecting and Using the Encoder Module,” on page 131 for a detailed discussion.

Sensor and Motor Polarity

The sensor polarity (i.e. which rotation end produces 0 or 5V) is related to the motor’s polarity (i.e. which direction the motor turns when power is applied to it).

AX2500/2850 Motor Controller User’s Manual 117