Delta Tau: PMAC Stepper Motor Interface (ACC-8S)

PMAC2's Accessory 8S (ACC-8S) is a 2-axis output board designed for easy connection to Stepper drivers. The step and direction outputs are RS422 compatible and are capable of being connected in either differential mode or single ended configurations for 5V input drivers. Flag input terminals are provided to allow connection of 12V-24V sensors or limit switches.

The PMAC2 can use a folded back signal from the ACC-8S to simulate the closure of a motor’s position loop. Jumpers are provided to allow the use of an external encoder for true closed-loop control. Being a two-axis accessory, velocity loop encoder input may be used if only 1 drive output is used.

ACC-8S is one of a series of I/O accessories for PMAC2. The interface to the PMAC2 is made using the JMACH connector cable. This cable is supplied with the board and is 24 inches long.

When used with the ACC-8S, the PMAC2 outputs a pulse train of variable frequency and constant pulse width. This scheme is known as Pulse Frequency Modulation (PFM).

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