Both dust collection auto on/off (wood) and air blast auto on/off (alum/plastic)

Since they’re there, I’m looking at figuring out how to make more use of the inputs/outputs on my OF controller (standard Buildbotics based) and VFD (Hitachi WJ200).

I have two digital outputs free on VFD for dust collector and spindle water pump.

On the OF controller breakout board I thought Load 1 (M7/M9 commands) for air blast (alum/plastic) and Load 2 (M8/M9 commands) for laser exhaust fan and air assist. Tool enable (M3 command) would be unused so far in the plan.

As I’m trying to sort it all out, I’m realizing the VFD can switch on the dust collector using a “wood postprocessor” without the air blast activating as well, but I’m not seeing how the opposite could happen, e.g., an “aluminum/plastic postprocessor” where M7 triggers the air blast, but somehow the VFD (or controller if necessary) doesn’t switch on the dust collector.

I’m new to CNC, postprocessors, and I/O so I may be completely missing something, or maybe it’s not possible with this set-up. In the end if it’s not doable, it’s not a big deal because I’ll mostly be working with wood, but curious if anyone knows a work-around to automate all those elements. Thanks

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Hey Martin,

do you remember when we discussed the different outputs of the Hitachi WJ200 (aka Omron MX2)?

Since the AL0..2 outputs are solid state relays which generally do not hold their state when you use them to trigger an external relay with minimal trigger current, and also are not dimensionated strong enough to switch a dust collector by themselves, I assume you mean the two open collector outputs on pins 11 and 12.

What do you mean with postprocessor?

Usually the two outputs on the VFD are to switch the spindle coolant pump and the dust collector on and off (this way you can also make that the spindle coolant pump runs a little bit longer after the spindle is stopped).

Regarding workpiece coolant, regardless of flood, mist or air cooling, you have the M7 and M8 commands. You would switch these coolants on by the CNC controller usually, since these commands that are made for this.

If I understand you right, when milling aluminium and plastic, you don’t want the dust extraction to run? This could be achieved in different ways. You could wire the CNC controller output that gets activated when you start one of the workpiece coolants (load-1 or load-2) to an input of the VFD and use the internal logic to make the output for the dust extraction only switch on when this workpiece coolant is off. This is the advantage of a good VFD: The internal logic. Would the solution that when one of the workpiece coolants is activated (with M7 of M8 commands), this makes the dust collection staying off be satisfying?

The other way would be an external logic. Load-1 or Load-2 on Onefinity Controller are XORed with the output 11 or 12 that switches dust extraction on.

As far as I remember the ‘tool-enable’ pin (usually M3 command on PWM spindles/router) does not work when a VFD is selected as tool, but I got to look if this is true. I remember there was a topic dealing with this.

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Thanks @Aiph5u . Yes, I do remember well. I understood a good part of it, but not 100% I see. I had hoped to keep pin 11 for the possibility of EDM function in a safety relay (which I haven’t set up yet). I also remember that the AL relay output was a solid state relay, but not that it couldn’t trigger a larger relay or contactor of some sort to handle the dust collector amps. Thanks for the reminder. Maybe the alarm relay output could handle the water pump which is very low wattage? And the dust collector on pin 12 open collector?

Well, my thought was to make roughly 3 post processor versions in Vectric: 1) for wood products in which the dust collector switches on (basically the normal post processor); 2) for alum/plastic which includes M7 command for air blast and somehow switches off dust collector; 3) for laser which includes M8 to turn on fume extraction and air assist (I don’t need flood coolant. Just want to trigger Load 2). I don’t think the VFD dust collector would come in to play with the laser because you have to switch from VFD to PWM spindle under tool configuration first. By the way, I planned on having the Load 1 and Load 2 pins trigger external relays.
Is this right?


Yes, very satisfactory. Thanks much. I somewhat wondered if that were possible, but I’ll have to look at the manual again to see how that would work. VFDs are pretty cool devices :sunglasses: I believe the VFD input method would be better than using outputs, which I’m pretty much out of.

Ok, well I’m using the laser as a PWM spindle, so maybe I could trigger a relay for laser fume extraction and air assist through tool enable instead? And keep Load 2 free? (assuming there isn’t communication to VFD to turn on dust collection, of course)
Thanks as always for your responses to those of us who are just learning the ropes

Hey Martin,

A spindle coolant pump or cooling station should be in the range of the AL0..2 outputs (you can try it out if it stays on with its current), but surely not a dust extractor, since either when connected directly it is much too strong for this output or when connected with an external relay, usually the relay’s control input can not ensure the minimal current (see the table above).

Ah, okay, with postprocessor you really mean postprocessor :slight_smile: I understand better what your plan is.


This is necessary since unlike the load-1 and -2 outputs on the original Controller, on the Onefinity Controller they are only able to provide small currents.

Since I didn’t have this use case yet, I am not sure at the moment which output function you would select to feed the second input of the logic (besides “run signal” or “frequency arrival signal” on the first). But you have the manual to and can have a look. I got to leave now until tomorrow evening.

Of course, since when ‘tool-type’ “PWM spindle” is selected (or the new ‘Laser’ and ‘Router’ tool-types as of firmware version 1.0.9, which internally still rely on the PWM spindle entry but with a few options invisibly selected), you have the ‘tool-enable’ pin that is triggered by the M3 command, and you can trigger more than one device from this output.

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Ok, I’ll try it.

Yes :slightly_smiling_face:

Ok, I’ll look in to it. I’m not familiar with VFD internal logic, but I’ll read up a little. Thanks

That sounds like the better way to go then, rather than Load 2.

So I had the chance to take a little look at the manual. I thought maybe the LOG1-LOG3 outputs with something like “Run” command and “Input x inactive” (connected to the M7 output signal of controller).

But apparently the LOG1-LOG3 is limited to combining two of the output functions only. I don’t really see anything that might work.

Except maybe MO1-MO3 which apparently need to be programmed through Hitachi software on a PC? Maybe the only option. Unless I’m missing something else. I couldn’t find much about the EZSQ programming in the manual. Must be a different manual.

Hey Martin,

inbetween, I also had a look at the manual. You are right, with the logic you can only use output functions. Unfortunately it seems you can not connect the state of a digital input terminal to the logic. But there is “Analog Input Disconnection Detection” which uses the state of the analog inputs OI or O to feed the output logic. As long as you don’t need this input for something else, this should work.

As someone who can solder and design pcbs, I would probably XOR the M7 of controller and the RUN output of VFD externally.


That gives me something to look at. I did see the “Analog Input Disconnection Detection,” so I can look in to how the controller output can communicate to the analog input.

Definitely an advantage in these kinds of things. I don’t have that skill. Thanks again

Hey Martin,

there are two different Load-1 and Load-2 outputs on the Onefinity Controller which are triggered by M7 and M8. The sockets with these names on the back of the Controller have +Vcc which means 36 V, while the pins 2 and 1 of the 25-pin I/O connector have 3.3 V. They are directly wired to outputs of the Onefinity’s AVR microcontroller.

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Ok thanks. Wasn’t aware of that difference. Good to know

Although now I’m thinking that maybe “Analog Input Disconnect Detect” might not work because A001 frequency source has to be set to 01?

Hey Martin,

we should test if this still works then A001 is not set to 01. Maybe A001 is only mentioned because usually you want speed control by a potentiometer or by a Masso Controller with the O and OI ports.

If it doesn’t, we got to control it externally. Possibly there are ready-to-use modules with screw terminals that require no soldering.

I don’t know how to use the MO1–MO3 inputs. In your Hitachi manual it refers to EzSQ but in my Omron MX2 version of the manual it refers to “Drive Programming”. Their software is called CX-Drive and the Drive Programming Manual they refer to must be this one.

Ok I like all those possibilities. Thanks much. I’ll see if I can figure something out.

For Hitachi I think it would be through what they call “ProDrive Next” software. Maybe the manual is similar enough to the Omron to get an idea of how it works. Thanks for the link

Hey Martin,

I just tried to understand the contents of MX2/RX/LX Series Drive Programming User’s Manual, but I have not the time to dive into this further at the moment. I have never used one of the proprietary VFD control softwares. I am not sure if the “Input Terminal Variables X(00) to X(07)” and “Output Terminal Variables MX2: Y(00) to Y(02)” that you can find in this PDF could be of use to us.

It is obvious that MO1–MO3 are functions that can be assigned to outputs 11 and 12.

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Hey Martin,

do you know the cheap relay modules with optocoupler and screw terminals that e.g. ebay is full of? The most simplest way to implement your logic would be to make that M7 via Load-1 triggers such a small relay, that in turn has its output in the line between VFD’s 11 or 12 output and the dust collector relay control input. This would mean, when M7 is on, dust collector is off (even if VFD’s RUN signal is active) (be sure that it’s the dust collector and not the spindle coolant pump :slight_smile:)

Do you already have the relay for the dust collector? I use Omron G4A with its 20 A for this but many people in North America use this “IoT” relay. You would interrupt one of the control lines of this relay with such a small relay with optocoupler, which has its control input connected to Load-1, and thereby switching dust collector off.

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Ok that sounds even more doable. Not sure that I could tackle the drive programming software or external XOR very easily.
Yes, I’ve taken a look at the online relay modules with optocouplers. I don’t have one for the dust collection yet. They seem to be mostly rated up to 10A. I’m guessing 10A might be a little low. Maybe the IoT relay you linked would be the best. I’ll be looking around. Thanks

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Hey Martin,

for the pull-up resistor on the open collector outputs 11 or 12 on VFD and for the relay module you still need a small power supply (usually for DIN-rail since it is assumed you have a DIN-rail in your control cabinet) like this one. 24 V is common in VFD cabinets in case you later want to use a Omron G9SE safety relay.

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Hello @Aiph5u, Ok, I’ll be taking a look at the whole circuit requirements, and I’ll make use of a 24v power supply for the VFD output and the relay module. I’d like to keep everything 24v if possible. And at some point I’d like to set up a safety relay as well. Take care

Hi @Aiph5u I guess unfortunately I’m still at a loss at how to use either the open collector outputs or the relay output on the VFD to turn on a dust collector because the relay output can’t handle the current, and the open collector outputs apparently require a flyback diode, which I don’t know how to add to the circuit.

I’ve read through this and previous posts again. As you’ve mentioned and is in the diagram in the VFD manual, on open collector outputs 11 and 12 on the VFD I should add a power supply and a flyback diode to the relay circuit. Does that mean the outputs don’t supply 24v power themselves from the VFD?

I was considering this relay module, which requires 35mA at 24v connected to the open collector outputs. That would be within the 50mA max spec for the output. But then with an external power supply I still have the problem of adding the flyback diode.

I also considered a simple SSR like this one which lists minimum control current of 5mA and max control current of 25mA. Also within the specs. Would I still need an external power supply and a flyback diode with a SSR?

At this point I’m also happy to go with the IoT relay that many use with the OF controller, but I don’t know how that interacts with an open collector output on a VFD.

So am I doomed to switch on my dust collection manually unless I can get someone to wire up a circuit for me with a flyback diode? :slightly_smiling_face:

Hey Martin,

every relay has a control input which is the coil that activates the relay switches, and a number of one or more switches that are switched by powering the control coil on or off.

The flyback diode is any diode connected across an inductor (= the relay’s control coil) used to eliminate flyback, which is the sudden voltage spike seen across an inductive load when its supply current is suddenly reduced or interrupted. A diode’s schematic diagram looks like this:

Do you see the diode above in the diagram from the VFD manual? It is wired in parallel to the relay control coil (RY). You can recognize the cathode pin on a diode by a color band printed on that side of the diode housing. The diode is wired parallel to the relay’s control coil, and its anode goes to pin 11 or 12 (the open collector output) and the cathode goes to positive output of your DC power supply. The negative output of your DC power supply goes to CM2.

Yes, on an open collector output, you need a power supply because the open collector does not provide any voltage. The VFD has some 24 V output, but this is just a positive logic voltage for the control inputs, I would not use it to drive a relay. Using an external 24 V power supply like the Meanwell MDR or similar which attaches to a DIN rail that you usually have in your control cabinet is usual when using relays on open collector outputs. 24 DC is also used by other devices like the safety relay Omron G9SE (datasheet). Depending on the maximum current that are allowed for the open collector output and for the relay, you would also possibly need a pull-up resistor to limit the current.

I would use a general purpose diode, e.g. 1N400x.

PS: I remember that the other day I posted a circuit diagram:

It has an additional manual switch for using the dust collector on other power tools like circular saw while the VFD can switch it on and off automatically (by the CNC) at the same time.

The relay switches both power wires (N and L) on and off which is more safe but of course you can also switch only one wire to the dust collector on and off by a SPST relay.