SD-800 - 8 Channel DB37 "Stepper Distribution" Board

The SD-800 breaks out the steps/direction signals from Kuper RTMC16, RTMC48, and OPCS A800 on a DB37 connector
into separate RJ-45 connectors. This simplifies wiring of step/direction signals between these cards and the stepper motor drive modules.

Description

The SD-800 board simplifies wiring of the DB37 connector provided by Kuper RTMC16 / RTMC48 and OPCS A800 stepper motor "pulse generator" cards to the separate stepper motor drives. Each motor channel's step/direction pairs are combined onto separate RJ-45 connectors, so that RJ-45 patch cables can be used to run out to each motor's stepper drive.

RJ-45 cabling makes it easy to swap or reassign motors to different channels, and to modularize each channel for maintenance.

Here's an SD-800 card with just the A channel wired to a stepper drive:


SD-800 card (top left) wired to a DB-37 rainbow extension ribbon cable to an A800 in an IBM PC.
A single RJ-45 patch connects the SD-800 to a DM-542 stepper drive (right) as the "A" channel.

SD-800's DB-37 connector	SD-800's 8 RJ-45 jacks

Currently there are only two revisions of this board, REV-0 and REV-A, which are identical except for small silk screen modifications.

SD-800 Circuit Layout

The circuit board's layout was designed with Sprint6 Layout, which is commercial circuit board design software that's about $50 for a license. The Sprint6 project file for REV-0 is sd800-REV-0.lay6.
Note: this file is only needed to make edits (changes/customizations) to the board design. To just print boards without making modifications, use the above .zip file.

What follows are images of the circuit layout layers as they appear in Sprint6 Layout and/or a Geber viewer (such as the open source tool 'gerbv'), along with board mounting dimensions.

SD-800 top and bottom layer (click for full sized image)	SD-800 board mounting dimensions (click for full sized image)
SD-800 top layer	SD-800 bottom layer
SD-800 photo top side	SD-800 photo bottom side

SD-800 Board Schematic

Sheet 1 of 1 (click for full sized image)

Installation and Configuration

When mounting the SD-800, size #6 screws can be used. Use all 4 mounting holes, and use rubber or nylon standoffs to keep the back of the board from touching metal surfaces.

Use cable strain relief when possible for the DB-37 cable, to prevent tugs on cabling from stressing the DB37 connector on the SD-800 card.

When wiring the RJ-45 cables to the stepper drives, follow the wiring diagram in the above schematics.

The SD-800 has only one configurable option: the resistor networks RN1 and RN2 which should be configured as follows:

• They should NOT be installed if the pulse generator outputs are TTL/CMOS level.


• They should be installed if the pulse generator outputs are open collector.

When installed, they pull up the steps/direction outputs to +5, which for open collector outputs can decrease noise pickup when these signals are floating. Noise can cause motors to creep, or run erratically and loose position. Example: moving only channel B in reverse may cause neighboring channels A or C to creep or run improperly, or the moving channel B may not run correctly and loose position.

When you're experiencing noise problems during testing, install the SD-800's 1K pullup resistors in RN1 and RN2. If noise problems persist, use a scope to check the step/direction signals at the motor drives. You should see the "steps" signal to normally reside at +5v, and fall to ground during stepping. The "direction" signal should either be +5v or GND during motor running, and not some value inbetween.