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E stop opto coupler


Try this:

Use e-stop 2. If Masso now works, simply remover the cover on the pendant connector and connect two wires to the pendant e-stop switch.  Wire these is series with your

other e-stop switches.  I did this on one of mine.




I would like to try that could you explain it in a bit more detail please?

Right now I have the estop wired to power down the Masso and the stepper power supply so if there is trouble and I hit the estop it just goes dead. Then on power up it needs the estop cleared before you can do anything so I go to the setting page and toggle the estop from low to high and that clears it. Then I go out of settings and home the machine as normal and it's ready to run. That's my work around until I get this sorted.


i can't really see any damage at all in the area where the resistors are but as I said I can see a tiny little flash of light when toggling the estop PB. I will send all I can to Masso though and see what can be done, thanks for the advice.



All I did was use the pendant e-stop switch as if it were one of the main e-stop switches.  To do this you must open the pendant connector that plugs into Masso.

Identify the two wires that connect to the NC  contact of the pendant e-stop switch (button).  Disconnect these wires from the pendant plug that plugs into Masso.

Solder a couple of wires 0nto these wires to us a extensions so you use connect them in series with the main e-stop circuit.  I drilled a hole in the pendant plastic

cover to allow the wires to exit when you put the cover back on the pendant plug.  ALSO you might want to consider using the relay board that Masso makes.  It has 6 relays

that can be actuated by masso outputs.  Handy.  Maybe you do this already.  Why remove power from the stepper PS when the e-stop will stop the motors in their tracks!

If I left anything out let me know. Happy to help if I can.


Hi Guys,

Just to correct a couple of misconceptions.

  1. Estop does not bring the Axis to an immediate stop, it puts the machine into feedhold and turns off the Spindle.
  2. If you want to bring the axis to an immediate stop then the Emergency stop output is provided. This is labeled ES and sits next to output 18
  3. A TTL Relay can be connected to the ES output and can be used disable the motor drives.
  4. You should not disconnect power from your stepper drives as this can damage them if you are disconnecting them on the DC side.
    For example disconnecting and reconnection DC power to Gecko drives will blow built infusible links.
  5. To stop the drives use the Enable / disable input on your drives using a TTL relay connected to the ES output. Wire as per your drive manufacturers spec.

I cannot comment on the bright light you see maybe it is arcing but the voltage should not be high enough for that.   [  Do not go towards the light 😉  ]
I strongly recommend that you test the Estop as per the document that Arie provided
You do not need to know what Optocouple is used. You only need to test and report the results. That will help tell the extent of damage.
With luck it is just the loss of the Pendant Estop and it may be repairable and if not you can still work without it.

Watch this video to see the relationship between Estop 1 and Estop 2. It is very simple.


Report back your test results and we can see where to go to from there.

Hope this helps
Cheers Peter


Hi Peter,

Is the ES output only controlled by the Estop input or is this output used in other events (driver alarm etc.)?

I ask because i want to use a relay with forced contacts and a reset button in my safety circuit, and use one of the contacts to operate the Estop input (and the other contacts to disable the stepper drivers and the spindle)

If Masso can operate the ES output in other events, i need to intergrate the ES output in my safety circuit.


kind Regards,


Hi Jarno,

The ES output is used by all events that trigger an Estop.

Cheers Peter

@jho I'm in the same situation as you in wanting to interface with a safety circuit. What forced contacts are you using? I can't find a 5VDC option that will work off the Masso estop output.

I also can't tell if the Masso estop is software controlled or if it hard wired with the inputs. Some more documentation on how the estop is set up would be great.

The only alterative I see is to rewire the pendent and touch screen estops into an independent 24V estop circuit an output of which would go to the Masso along with other circuits. The Masso estop output wouldn't be used.