Estop Wiring Via Breakout Board

Trying to wire an external Estop. On the breakout board the Estop is Pin 23, so do I wire Pin 20 (3.3V) or Pin 25 (Ground) to this through my Stop button NC? I noticed the NO and NC settings in the firmware but cannot get this current wiring to work.

I also don’t seem to get 3.3V when I check that against ground with my multimeter. Maybe this is my problem? Do you have to activate the 3.3V pin somewhere in the software?

Hi Nick,

I’m planning out my wiring for a unit on order. Did you ever get an answer on this?


Hey Nicholas, hey Jeff,

a switch from EStop (Pin 23) to Ground (Pin 25) (=Logic low).

If you connect a “Normally Open” Switch (NO), in the “I/O Configuration” Tab, “estop” must then be set to “normally open”. If you connect a “Normally Closed” Switch (NC) you must set it to “normally closed”.

Pin 20 should measure 3.3 V against ground.

3.5.25-pin I/O Port - Buildbotics Controller Manual

23 | EStop | I | Open, VIL | Emergency stop switch
VOL    0       0.76 VDC  Logic output low
VOH    2.6 VDC 3.3 VDC   Logic output high
VIL    0       0.6 VDC   Logic input low
VIH    2 VDC   3.3 VDC   Login input high
V3.3           3.3 VDC   Voltage found on V3.3
                         Output when unloaded

Note: The National Fire Protection Agency (NFPA 79) requires that the class of emergency stop button be determined through a risk assessment. The soft “emergency stop” button on these web pages and the estop pin (pin 23 on the DB25 I/O connector) are both software controlled, and cannot be used for safety. If your risk assessment requires an emergency stop button to be installed for safety purposes or mission critical applications, then Buildbotics LLC recommends installing a “listed“ hardware Emergency Stop button in line with system power.


Thanks for the info.
I’m thinking about putting the controller on a UPS and if the power goes out to the 2nd circuit which will be the router and vacuum, I would trigger the estop on the controller via a relay (since “pause” is not remote). I’m not sure if it’s worth using the UPS as I haven’t read that it’s a big issue but since I have a spare doing nothing right now I figured I could put it to good use.
Even if I don’t use the UPS, this is good to know information.
+1 on the enhancement request for a Remote Pause button.