CB CNC Part 9 / Wiring Contactor Unit to On/Off Switches

Ok in this video I am going to wire the contact up to this on off switch here. I will zoom into the different components and just talk about them for a little while now.

I am not sure if I bought the right circuit breaker. This is a 16 amp breaker.

This is the first contactor that I bought and it has two normally open channels and two normally closed. And for what I’m using this for I can still use this, but a few days ago I got a little bit worried that I might have bought the wrong one, so I bought a second one that has all normally open channels going through. I think I might actually just use this one.

For what I’m going to be doing I’m going to only need the open and at least this way around I can put my live and neutral wire through to normally open, plus the wire that will go to the on and off switch.

With this particular switch I would only have the live going through and the neutral would come around this. So I don’t know if that’s necessarily the right thing to do.

So the thing to mention about the switch is it has one set of normally open – which is this side here the brown one. And one set of normally closed contact, as well as contacts for the light which is this thing here. I’m not sure how good this thing is.

This section of the controller will be where the main source of 240v power enters the enclosure, and is sent via the contactor to the VFD and PSU.

As I have not wired a contactor before, I drew some references diagrams from sources I found online. There seemed to be slight variations but the main similarity was the on switch should be normally open – meaning its two terminals are only connected when the button is pressed. And the off switch is normally closed which means the two terminals are connected until the button is pressed, breaking the connection.

I will reference all these sources in the description below.


I am going to test as much of this build out before placing things into an enclosure. I am making a test board with a terminal to feed power from, and a place to mount the switch and contactor unit.

I’m going to plug it in and see what happens. I think I have wired it up correctly. This is obviously the exciting bit.

Definitely not wired it in correctly.

Ok here goes the second attempt.


Ok this is the third iteration of the wiring. I am now using a third reference source. I haven’t wired the light which is in this particular switch.  I am going to plug it in and see if it works.

So that tripped.

So I am obviously running into problems, with the contactor either remaining on, or tripping the circuit breaker. Eventually Nathan (who I share this studio with) popped down and noticed I had an 110v coil on the contactor.

I got a bit stuck because it didn’t seem to be doing what I thought it would be doing. And it’s turned out that the coil requires 110v as opposed to 220v which is what I’m supplying it with. I only noticed this because Nathan can down from OpenTronic and asked me why I was taking so long to do this, and he had a look, there you go. He suggested I could swap the front panel out with the 220v coil on the other contactor.

You should really check his channel out – he actually knows what he’s doing.

After doing this, I was still having problems and a quick check with the voltmeter revealed a surprising problem with the on/off switch itself.

Ok that says NO, normally open which means these two terminals should not be connected , but they are. This says NC, normally connected which means these should be connected and they are not.

In the same way the contactor unit has modular parts which could be swapped, so does this switch. But before anyone starts complaining about cheap Chinese parts, these components are designed to be fixed by a person. You are not designed out of the component, which is why it is easy to make such a mistake. Maybe the assembler had a hangover as well. Often items for western markets are made so the user can’t even open, let along fix them. And in any case, if everything worked perfectly how would any of us learn?

I could take it apart and re-wire it but instead I’m going to just swap the connections so I can finally check my wiring.

Off switch, should have a contact and the one switch should not.

So I think the rule is with whatever component you buy, especially if they are second hand or on ebay just go over them with the voltmeter to check that they have been assembled correctly.

So I’ve wired the light on the actually switch onto the l1 and L2 terminal, which go to live and neutral. I them have a live wire coming into the normally open terminal at the end of this unit, and it comes out to – really thing should be red – to the off switch which should be normally closed. And then carried on going though the switch which is A1 which is the entrance terminal to the coil, and then A2 goes directly back to neutral.

This isn’t going to look like it makes much sense from your perspective.

So the on switch which is normally open has a wire coming in from live, then going from the next terminal along back to the 4th normally open terminal at the bottom side of the contactor.

So that creates a latching circuit – I think it’s described.

When I know what I’m actually doing and I’m confident the circuit is correct will time these or put crimps on them, and do it properly.

So we’re looking at these lights here, these LED’s

Thank fuck for that it turns on.

So the last thing I’ve is put this circuit breaker in between the live coming in and going to the switch. If that is off, pressing the buttons does nothing but I’ve wired the light ahead of the contactor unit, so at least I know there’s power coming into the unit. If I turn that on and press the button, the contactor activates.

So I am getting a new switch sent to me, but the main thing is I know how this now going to be wired into the enclosure.

I cut slots in some trunking to make cable tracks for a mock up panel mount. It’s going to be a really tight fit with little room to upgrade so I have to think about this a little more carefully.

In the next video I will either work a little more on the layout, and I have an idea about a modular control box, or I may test another component such as controller which I have yet to turn on. When I began designing this machine I wanted to use proximity sensors to measure the minimum and maximum distances between the x and y axis, so it may be prudent to work that out before put thing in an enclosure.

Anyway thanks for watching.

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