RoboteQ AX2850 Using the Encoder Module to Measure Distance, Using the Encoder to Measure Speed

Installing, Connecting and Using the Encoder Mod-

TABLE 16. Effects of Limit Switches 3 and 4 on Motor 2

SW3	SW4	Motor 2 Fwd	Motor 2 Rev
OFF	ON	Allowed	Stopped
ON	ON	Stopped	Stopped

In Single Channel Mode, limit switches 3 and 4 are used. This is to allow direct connection of an encoder on the inputs for channel 1 and direct connection of switches on the inputs for channel 2

TABLE 17. Effects of Limit Switches 3 and 4 on Motor 2 in Single Channel Configuration

SW3	SW4	Motor Fwd	Motor Rev
OFF	OFF	Allowed	Allowed
ON	OFF	Stopped	Allowed
OFF	ON	Allowed	Stopped
ON	ON	Stopped	Stopped

Using the Encoder Module to Measure Distance

As the encoders rotate, their quadrature outputs is automatically processed and incre- ments/decrements two 32-bit counter inside the Encoder Module. There is one 32-bit counter for each of the encoders.

The counter values are stored as a signed binary numbers, ranging from -2,147,836,648 to +2,147,836,647 (Hexadecimal format of value 80000000 to 7FFFFFFF respectively. When the maximum or minimum counter values are reached, the counters automatically roll over to zero.

The counters can be read and set using the commands described in “The Encoder Module contains its own Microcontroller and firmware in Flash. When present, it responds to a large set of dedicated commands and queries via the controller’s serial port. See “RS232 Encoder Command Set” on page 155.” on page 82.

Using the Encoder to Measure Speed

The encoder module will automatically compute rotation speed for each encoder. The resulting measured speed is a value ranging from 0 to + 127 and 0 to -127, where 127 rep- resent a relative ratio of a maximum speed value chosen by the user.

For example, if the encoder module is configured so that the highest measured speed value is 3,000 RPM, then a reading of 63 (127/2) would be 1,500 RPM.

The relationship between the measured speed and the actual speed is a factor of two vari- able parameters: a Time Based period value stored inside the Encoder module and the Encoder’s number of Pulses per Revolution. Note: the Encoder’s number of Pulses per Revolution is not stored in the controller.

The Time Base is a number of 256us time intervals between two counter reads.

80 AX2550 Motor Controller User’s Manual Version 1.9b. June 1, 2007