Emergency Stop Board

The emergency stop board watches every e-stop contact in the cell (operator panel, teach pendant, remote pendants, perimeter stations) and drops the drive-power contactors through hardware relays the moment any of them opens. It's a safety-rated card built to fail into the stopped state.

Physically it sits on or near the operator panel inside the cabinet and terminates the EES/EAS input pairs from the cell along with the MCC output that switches the servo-amp DC bus contactor. Every input pair is monitored redundantly, which is why a single conductor break in one leg still trips the board even if the other leg looks fine.

Trouble almost always presents as a robot that will not come out of e-stop. Techs read the pendant fault, expect the usual suspects like SRVO-001 (operator panel e-stop) or SRVO-002 (teach pendant e-stop), reset, and watch the alarm reappear inside a second. That's the fingerprint of a stuck input somewhere in the loop.

Selection has to match both controller model and safety rating. Boards from R-30iA and R-30iB cabinets are separate part numbers, and the DCS-capable variant carries extra monitoring logic the standard board does not. Order by the exact part number stamped on the label of the failed unit.

Compatibility limits: any change to this board or the wiring it drives requires a documented risk assessment on the cell and a functional test of the whole safety loop before returning to production. The rule is straightforward. If you replaced anything in the safety chain, prove the stop still works before you press cycle start.

Troubleshooting starts with a continuity check of every leg of the e-stop chain, one contact pair at a time, with the pendant unplugged and each perimeter button pressed in turn. A single high-resistance junction (corroded screw terminal, backed-out ferrule, cold solder in a remote pushbutton) looks identical to a bad board from the alarm log alone.

Practical example: a cell that kept dropping SRVO-004 (fence open) at random turned out to have a doorstop-mounted switch whose plunger froze in cold weather. The intermittent contact read as a fence excursion. Fix the field device before condemning the board.