E Stop for controller & VFD/Spindle Questions

This has probably been answered, and I have looked through numerous other posts about this. My understanding is the simplest way to have an E-stop for stopping the machine and simultaneously the spindle via g code, is to use pin 23 on the breakout board (using the software e-stop)? Would anybody who has done this or enough knowledge on this be able to answer this? If something is to arise, I want one button to hit to stop all motion and spindle torque without killing all the power.

I have everything for my 2.2kW spindle here but want to get this squared away before laying out the wiring and such. My plan is to have a main power switch for turning on the VFD and controller at start up that will double as a SHTF power kill.

If somebody wants to simply explain how to wire an e stop to pin 23 and what switch is appropriate, I would greatly appreciate it! Thanks in advance.

Hey Ryan,

this goes this way. For the switch, a SPST is sufficient. You can use either “normally open” (NO) or “normally closed” (NC) type since this can be set inside the Onefinity Controller. If unsure, you can buy one with both NO and NC, like this one.

There is also much information in this thread.

If you have a setup with a safety relay on your VFD (as shown here), you can also wire it the other way: The Emergency Stop switch is then connected to the safety relay and this stops the spindle at the VFD and this triggers “estop” pin 23 on Onefinity Controller. This would have the advantage that the VFD would also stop the running program on Onefinity Controller in all other error cases the VFD may report.

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Sorry meant to say button not switch for the e stop but I understand what your saying anyways. I don’t plan on having the safety relay setup. When wiring pin 23, does this need to have any contact to the vfd? Or will communication be sent through the RS485? I still don’t understand if pin 23 produces voltage or if it’s just an voltage input that is needed to trigger?

Under the default configuration, pin 23 to ground closes the NO circuit, triggering the E-stop.

The RS485 spindle will stop. No connection to the VFD is required.

Thank you! Looks like I can use pin 25 to achieve the ground. Trying to make this setup as simple as possible but also safe.

For restoring the system after an e stop is triggered, can I accomplish that through the software e stop button (on the controller screen)? I’m also wondering what happens when you release the external e stop?

Yes, pin 25 should suffice. I believe that is what I am using.

As a weekend warrior, I cannot speak to the proper or required cases for software E-stops vs. hardware E-stops in a commercial environment, but I’m sure someone else can chime in. I have an additional hardware E-stop separate from the software E-stop in case something REALLY goes wrong.

Releasing the E-stop resets the controller. You will lose all home and zeroes. The spindle will remain off.

Ok great, just wanted to make sure adding the external stop will behave the same as hitting the on screen stop.

Yes, the external “software” E-stop (pin 23) will behave exactly the same as the button on the screen.

Just not to be confused with an external hardware E-stop that cuts all power.

Correct. Thanks again

Hey Matticustard, hey Ryan @PaquetteWoodworks,

Just in case someone is interested in the subject, I tried to explain this in the thread mentioned above

In fact you need both. What Ryan refers to is if there is something to abort quickly and stop all running motors, e.g. to avoid harm to humans (or animals), but without cutting power to everything. In fact VFDs with spindles running on them don’t like sudden power cut at all and can even be damaged. However what you always should have too, is an emergency switch preferably at the entrance of the room, with which you can safely cut off power on all hot lines for the entire room, for the case of fire.


My last concerns would be if a braking resistor is necessary? I’m sure every VFD is a little bit different on what it can handle but the resistor seems like a good idea if power goes out or is cut off for emergency. I have the Huanyang and still searching for an answer to this.

If you did not previously tell Huanyang you wanted the VFD with braking capability, your unit probably does not have the feature.

I have a brake on mine. My unit stops very quickly. It’s nice peace of mind. But I can’t say whether it’s really necessary in the grand scheme of things.

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Ok no I just ordered the kit of Amazon. My understanding was if the spindle is running and power is suddenly cut off, the free spinning spindle would act as a generator and return excess current to VFD possibly causing damage?

Hey Ryan,

every VFD has a braking chopper circuit. The external resistor is an extension to allow for more power to be absorbed. The less resistance and the more power rating the resistor has, the faster the spindle can be brought to standstill or the bigger and the faster the jump from a high to a lower speed setting that can be achieved during operation. If the jump you request is too big or too fast for the chopper circuit, the VFD may trip.

You can choose what the VFD does when you stop the spindle. You can adjust a setting to either let the spindle coasting when stoppped, then it can take a longer time until it stands still. In this case the spindle is disconnected from the VFD on all three phases. Or you tell it to decelerate which means braking with the chopper circuit. In this case the current that the spindle generates is absorbed by the chopper circuit and transformed into heat inside the braking resistor. If the jump from high to low speed is too big and too fast, the VFD may trip in order to prevent overcurrent and overheating inside the VFD. On my VFD, you can tell the amount of speed reduction per time unit, in order to match the resistors capability, I don’t know on the Huanyang.

In the manual of my VFD, two possible braking resistors matching the VFD model are refered to with a parts number.

What you can do is 1. see if your HY model supports an external braking resistor at all 2. If so try to find the information on the recommended ohms and watts values.

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Just for clarification. If the unit trips, doesn’t it enter coast mode automatically to prevent damage?

Hey Matticustard,


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Ok that clears that up for me. Ill have to look into the programming capabilities of my VFD and see what’s possible. I did not know about the internal resistor.

Found this in case anybody is looking for a better on/off switch solution. Going to order this soon and see how it works.