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Julius Wilkko
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935 Posts
Discussion Starter · #1 ·
Hi!

Since this subject hasn't been discussed before, I decided to add few lines. It can be useful for some of us home racers. Slotcar motor generates all kinds of electro-magnetic interference (EMI). This interference can be conducted via copper wires from motor to AC socket outlet or radiated directly from motor to surrounding devices. Usually it's radiated RF-interference and visible on TV screen. So, if your kids are racing and at the same time you want to watch Emmerdale or Bold and Beautiful on TV - you may have a problem.


I'm amazed how some manufacturers don't bother to reduce EMI at all. You cannot find EMI-suppression components in FLY, Proteus or Cartrix car at all. Naturally serious racers will remove extra components but for example most common EMI suppression method, 100nF capacitor across motor +/-, does not have any affect on car performance. Chokes such as in NINCO or Carrera won't tolerate excessive currents and should be removed if the car is upgraded with high RPM racing motor.

Here's circuit collection how different manufacturers have tried to reduce EMI

Scalextric/SCX:



NINCO:



Carrera:



Cheap chinese 1:32 set car:



2,2nF = ceramic capacitor, 2,2 nanofarads
22nF = ceramic caacitor, 22 nanofarads
10nF = ceramic capacitor, 10 nanofarads
100nF = ceramic capacitor, 100 nanofarads
6,8uH = choke, 6,8 microhenrys
10uH = choke, 10 microhenrys
22uH = choke, 22 microhenrys

The last car on the list is from cheap track set similar to Artin. Price of the car is 6euros and still it contains 5 EMI suppression components. This is not price issue, so I wish that some manufacturers would take EMI more seriously.

If you have a car that disturbs your family life, all it takes is some inexpensive components and basic soldering skills to reduce EMI. Remember that soldering these components is not 100% cure, but in will suppress some of the disturbance.


Julius

PS.
Serious racers should also pay more attention to this subject. Timing sensors and computers operating your track can also catch interference. Need for EMI reduction will increase with introduction of new digital systems.
 
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Julius Wilkko
Joined
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935 Posts
Discussion Starter · #8 ·
Hi !

Soapy, choke is not a resistor, it's an inductor. In practice thin wound copper wire. Voltage drop across inductor is small, but inductor/choke resists fast voltage transients that try to go through the component. This is how it suppresses EMI. Fast voltage spikes generated by motor are attenuated by choke. What's the difference between choke and inductor then? It's just one of those things where different people are using different terms for the same thing.
Usually electronics world calls small inductors that look like resistors as chokes. When you have a component where copper wiring is clearly visible then it's usually called inductor.

Tropi, it's European CE regulation that dictates the maximum allowable limit of EMI disturbance. Thing is that nobody controls CE regulation. Manufacturer just tells that its product will comply certain CE regulations. If you browse FLY car box you can see letters "CE" there. This means the company has in theory tested its products and they are within allowable limits. Also Proteus Lambourchini box contained CE markings although it's my worst car ever disturbancevice. One can ask have they just printed CE to their boxes and hoped for the best. How can other manufacturers get away with no suppression components installed and others have several components installed although motors are about the same with both.
I'll take a photo of that cheap 6e (£4) car shortly. Mostly I disassemble those and use pinion, motor and rear axle for my Revell easy kit cars.


Julius
 

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Julius Wilkko
Joined
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935 Posts
Discussion Starter · #14 ·
Yes ... I knew people wouldn't take EMI seriously
... and some racers seem to even think EMI directive as government conspiracy to reduce their car performance. Beware the EMI police!


But seriously - it's not against the law in any country to remove these filter components. The worst that could happen would be 180Kg bodybuilding neighbour who finally figures out link between your slotcar track and disturbances on his TV screen.


Julius
 

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Julius Wilkko
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935 Posts
Discussion Starter · #16 ·
Hi!

Here's a picture of that cheap £4 car for Tropi



Usually I just salvage parts for my Revell EasyKit cars. Here's modified Mercedes chassis.



I KNOW !! There are no filter components at the picture, those were installed to the car afterwards. Really. I guarantee i did the soldering. You can send EMI police to inspect me if you have any doubts.




Nice looking and very cheap 18e (£13.50) car.


Julius
 

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Julius Wilkko
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935 Posts
Discussion Starter · #18 ·
Cars are from nordic harware store chain called "Biltema". They have shops in Norway, Sweden, Finland and Denmark.

http://www.biltema.se/index.asp

in "sök" =find just write: "bilbana" this is slotcar track in swedish.

Julius
 

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Julius Wilkko
Joined
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935 Posts
Discussion Starter · #19 ·
Porsche seems to be Art n:eek: 45-353. Apparenly they have a web-shop but I don't know whether they deliver outside nordic countries or not.

Julius
 

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Julius Wilkko
Joined
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935 Posts
Discussion Starter · #22 ·
Hi!

Difflock, motors are mass-produced items and there is some variation in charasteristics of produced items. You can have a good EMI motor or bad one. Apparently you had good luck with your Carrera car. Same thing applies to TV/video. EMI-CE regulation is intented to ensure that you would have minimum interference between different devices. Without regulation it would be lucky chance every time you buy a new device.

Julius
 
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