Radio Interference

When I am in the workshop (especially on a Sunday) I like to listen to the radio. However the issue I have is that I have electrical interference when I switch on my CNC mill. The radio reception (FM) goes fairly quiet and of poor quality. Power the mill off and all is as it should be.

Is there some sort of gadget I can get to stop this electrical interference?

Matt

Have a look at Nicola's post from last week, it was the light she uses when using the CNC, could be a similar problem.

It is possible that your CNC is feeding "noise" back into the mains..

I was concerned that my VFD would do this to the detriment of our Radio and Tv, and that of neighbours. It is fed through a socket incorporating a filter. Over the last 17 years, there have been no problems reported to me.

If the problem is being radiated, the CNC would probably needed to electrostaically shielded, possibly cables as well.

The licenced radio experts on here may wish to comment.

Howard

Is the radio mains or battery? I ask because one of my VFDs sent mains borne interference to another piece of kit, cured by wrapping the mains cable through a ferrite toroid

Duncan, the radio is mains powered. I think it will take batteries (not sure) so that is a worthwhile experiment to see if it is mains fed.

Matt

Well, I can now advise that the radio (running off batteries) id not affected, so it must the CNC feeding back nasties into the mains. I'll see what I can find to try and stop this. As Duncan said, a ferrite toroid is worth trying.

I suppose I could try something like this on the machine:

https://www.ebay.co.uk/itm/BELLING-LEE-6A-250V-IEC-RFI-EMC-MAINS-INPUT-FILTER-WITH-TRANSIENT-PROTECTION/163883963164?hash=item26283ed31c:g:1zMAAOSwpXtanBSx

Matt

The easiest way would seem to be to feed the CNC from a socket with a builtb in folter. Don't where mune originated, I got from the skip at work!

RS or Farnell will most probably have something suitable. It looks as if a stand alone, inline filter might be under a tenner, but a filtered/suppressed mains socket would be more.

Just looked and RS offer a number of filtered 6 amp IEC socket from about£12 upwards. The bad news is that the cheapest 13A double filtered socket is £48.58 (probably + VAT )

Look around Google and see what you can get. (I fear that is unlikely that there would enough space inside a wall box to wire in an inline filter to the feed to the socket to keep the ring main intact Possibly it could be done using a separate external enclosure to feed the socket through a filter as if it were a spur off the ringmain. )

HTH

Howard

Thanks Howard, I shall do some research and buying tomorrow!

Matt

I used what is described as 'Large Ferrite Core Toriod 2.2 inches' but he doesn't seem to be listing them any more. Plenty similar but a tad more expensive. A socket with built in filter would be easier

Edited By duncan webster on 14/02/2021 20:39:57

Well, I thought I would have shufty inside the dark corners of the Syil control box. Low and behold was an in-line EMI filter,

Can I assume that this is faulty considering the above problems? I'll order another unit (cheap) and see if it has any effect.

Matt

When you say switch on. Is this when running or just powered up. Just a thought. I had same trouble with my lathe & it turned out to be the LED light over the machine. Sorted now & that was Dab radio.

To clarify, I mean that whilst the machine is powered up - ie switched on and remaining on. As Soon as the power is switched off, then normality returns and the radio burst into life!!

Yes, a friend suggested a DAB radio but the reception is not great here...

Matt

Have you tried running the CNC system with the mill motor off?

Dave, the motor isn't even running and the PC isn't switched on. The Syil is merely powered up awaiting action!

Matt

Used to get interference from one of my old cars, sounded like the spark

ticktickticktickticktickticktickticktickticktick

would speed up and down with the car gearchanges

I have similar problems with the DRO on my lathe and the adjacent mini HiFi; when the DRO is on, I can't get any kind of DAB radio signal. Whether FM is affected I know not as I've only ever used the DAB. No effect with CDs or playing from the USB.

Matt, I was wondering about continuity of earths, power supplies have a degree of earth leakage. For instance you filter diagram shows two earths, one from the mains the other must be from the filter case otherwise the load side has no earth connection.

My 15 year old Warco supplied DRO interferes with classic FM as soon as it's switched on, how does that happen & any easy solutions? The 2 year old one is OK.

Tony

It's just a diagram thing. Usually both sides are earthed inside to the metal case. As its purpose is removing muck from Live & Neutral, it's not unusual for filters to only have one earth tag. The safety earth might be provided by bolting a filter to the metalwork, but more likely it's done somewhere else as well.

The problem may be at the receiver too. I have at least 3 FM/DAB radios where the input filtering is pathetic! It might be necessary to put a filter close to the radio's mains input, which is often easiest to do by looping the cable several times through one of Duncan's toroids.

There are filters and filters! The one shown in Matt's picture is reasonably good but not exceptional. It may not be effective at the frequencies zapping the radio. Rather than replace it, I'd put another one in.

Matt's evidence suggests his radio's mains lead is playing a part. It could be feeding muck fed from the CNC along the wires, or the mains cable could be acting as an antenna and receiving transmitted waves. Either way, a mains filter close to the radio should stop unwanted signals penetrating it's sensitive innards through the power cable.

Dave

At work we have a DAB radio (Planet Rock at the moment), when I put a tool battery in the Hitachi charger it pulses interference into the radio and the sound is cut off during each pulse.

Ed.