M-Stop Electrical Specifications

X-Series and R-Series Actuators
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curtis_layton
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M-Stop Electrical Specifications

Post by curtis_layton » Fri May 22, 2020 10:07 am

There was a question recently about the electrical specifications for the m-stop input to the x-series actuators. The m-stop signal uses the two "extra" pairs of wires in the Ethernet connector. Using the standard wire color convention these wires are blue, white/blue, brown and white/brown. In the actuator these pairs are connected between the two ports so the signal gets passed through the actuator (even if it is off).

For electrical revision F and newer (the most common) the Ethernet connector pinout is as follows:

1: TX+
2: TX-
3: RX+
4: M-STOP+
5: M-STOP+
6: RX-
7: M-STOP-
8: M-STOP-

For modules with electrical revision before F (less common) the Ethernet connector pinout is as follows:

1: TX+
2: TX-
3: RX+
4: M-STOP+
5: M-STOP-
6: RX-
7:
8:

The m-stop system is designed to run with a 5V nominal input, with 5V being active (motion is allowed) and 0V being stopped (hold position or motor off). It is okay for a small amount of variation on the input (4.5V to 5.5V). Inside the actuator the m-stop signal is attached to an optoisolator (Broadcom ACPL-M21L-500E) through a 1.6K series resistor. A 5V TVS diode is used to protect the input from ESD. Note that the TVS diode has a 6.2V standoff voltage. Because of the optoisolator, the ground signal must be connected (m-stop-) or the m-stop will not function. The m-stop input will most likely work with voltages lower than 4.5V, however it is not guaranteed.

Each actuator will draw ~2ma of current on the m-stop bus. For applications with very long runs of cable, make sure that the voltage input to each actuator stays above the minimum (4.5V). For normal use cases in our robot kits this is not an issue.
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