Reasonable priced solution to EMI issues?

I regulary have som problems with what i think is EMI issues.
I have a garage connected to a single circuit breaker with ground fault detection.
I have build a enclosure that have outlets to shapeoko, LED lights and Spindle on the inside. On the outside there are a outlet for vacume and switches to controll all of the outlets.
This is connected to one of my outlets in the garage throgh a powercon-connector.

The problem is if i try to run the vacum(or compressor) or starts or stops the spindle when connected to the outlets of the enclosure, I get disconects in carbide motion.
If i run the equippment from another outlet in the garage (retractable extension cord) i dont have the same problems. Drawback with this sollution is that i have to run with the enclosure doors open.

And now for the real question:
I was browsing around the other day and found this site for LED-Transformators(sorry it is in norwegian):
And was wandering if this might be a viable sollution. I did google the product name and found out that this comes in different sizes and shapes and from different vendors. Would this device be suitable to suppress noise from the spindle,vacum,compressor and other noisy equippment and if so wich rating should the EMI filter be?
Edit: Would it stop EMI from entering the connected equipment or leaving or maybe both?

Best regards.

Please contact us at — we’ll do our best to work through this with you.

Was really not looking for a support case here, rather a discusson on how to remove unwanted EMI and some feedback on the avaiable products on the market :wink:
I have found a solution that works when im doing important project and can live with that for now.
I also have tried the usual stuff like:
-Routing the powercord away from the rest of the wires (Suspended from the roof while the other cables run trogh the cable chain)
-Changing out the stepperwires to shielded ones (This fixed the random disconnects when running a project)
-Measuring the earth connections in my garage (Its verified good by electrician)


How do you know your problem is “EMI”? Those two tools are high inrush current items. They will drop the voltage at their plugs quite a bit if your wiring isn’t sufficient to provide enough current. You may be experiencing instantaneous low-voltage effects.

Ideally, each tool should be on separate circuits from the source, as well as your CNC electronics & PC.

They’re high inrush current yes, and there’ll be a voltage drop, but switching supplies are inherently less vulnerable to low input voltage issues so may or may not be an issue depending on the response speed of the PSU and severity of the low voltage transient.

The other thing the high current motors are likely to do, if they’re not appropriately suppressed at sourse is create a strong pulse of EMI.

It may be worth adding a noise suppressor such as the one listed, these filters are very common and also used to reduce the noise from VFDs. That particular one is a single stage with pretty common capacitor and inductor values, there are also double stage versions available and different capacitance and inductance values. Here’s a standard commodity one on Amazon UK

You can also pay 5-50x what they’re worth by buying them as “power conditioning” multi-socket leads from the likes of Belkin. Some vendors such as Furman Power do actually make more complex and capable power filters for uses like recording studios but a dual conversion UPS for the computer and Shapeoko is arguably a sheaper and more effective solution.

The question with the noise suppressor is whether to use them at source to try to isolate the noise from the motor (vac or compressor) from the mains wiring or to use them to shield the sensitive components such as the Shapeoko.

It’s worth talking to the support team as they’ve worked through this problem with quite a few people but if you want to try some stuff some EMI filters in the power lines are unlikely to make things worse.

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Mostly beacuse I also gets disconnect when turning them of . Also the wiring is 2.5mm3 wich should be plenty for these usecases.


If you don’t know me, but I am coming up on 5 years of owning my Shapeoko, and while I have removed 99% of my disconnects, that also means that I still get them once and a while.

The 99% solution for me (after moving all the 120V wires away from the 24V/USB wires, and replacing my old GRBL board with a Ver 2.4 board) was to run another clean 120V line into my shop to run ONLY the CNC. EDIT ADD: I ALSO replaced my DeWalt with a Makita router (Because I let the smoke out from flying aluminum chips…which is where I came up with the sock pre-filter idea) about the same time I ran a new line into the shop and was wondering if the DeWalt was part of the reason, hmmmm)

The 0.9%: It appears that I only get them during the winter months when I am machining wood and the humidity is near single digit. I fix that problem by increasing the humidity (ok, I just spray some water inside of my enclosure). EDIT ADD: Adding additional earth grounds did nothing for me…)

But there is still that 0.1% that I’m chasing…(Metal OR Wood) Disconnect.


I see you are in Norway and I will assume you are running 220v like most of Europe. Many have grounded their dust extraction and solved a lot of problems. In your case it may be noise introduced by noise from the start up of your vac or other accessories. Try using your laptop unplugged if it is a laptop. If you are using a desktop type computer you might try running an extension to another circuit located elsewhere. The separation of the computer from the same outlet the Shapeoko and other accessories has worked for some. EMI is hard to pin point but by process of elimination you may be able to isolate your noise/static component.


Problem is that i get the disconnects when only running one equippment at a time.The Dewalt router OR vacume OR compressor.

Unfortunally that is a little bit hard to do, beacause of the way i have rigged my emergency button :roll_eyes:

I have ordered two of these to experiment with:
From a almost local(Sweeden), very reputable vendor. 20$ each, free shipping and two days delivery. It also have a datasheet. I feel it´s important with a little warning regarding the posted amazon link above:The store that are linked to have one onestar review that says this store does not ship anything.

I was also wandering if there are anyone that have som insight on the frequency levels of the noise that i could expect from the dewalt router and evetually flourecent lightning?

Edit: I will try to take some pictures and draw up some schematics in the next few day to clarify my setup.

Best regards.

I had horrible EMI issues when i would run the vac or if i ever touched the metal. I talked with some helpful folks here on the forum and ended up being able to solve all my problems for the cost of a roll of wire and some plugs. see the photos below. I just grounded everything to the screw in the junction box and I haven’t had an issue one since that day.

here is kind of an overview photo.

First i ran a wire to the back of the frame, grounding that.

Then i ran a wire to one of the bolts on my router casing.

Then from my router bracket to the dust collection hose. I stripped the shielding off the wire so the static could get all sexy with the the bare copper. It hasn’t caused any clogs or obstructions thus far. you can see the wire in the hose in the photo.

It is all tied back to the box.

Hope that helps. It worked wonders for me and I didn’t have to spend a fortune in other solutions first.



That’s a good example of “star grounding”


Plugging your computer into a different outlet is a way of using your house wiring and appliances as a large LC EMI filter.

If you want to try grounding your machine here’s some more discussion of how to do it;


Remember to use star lock washers between the wire terminal and the aluminum, it will cut through the anodizing in multiple points and make a better connection. This works for me. I also taped a bare copper wire all along the dust collection hose to pick up static eletricity.


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