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OK, I've just stripped a Carrera Bentley of its EMI ballast and proceeded to power it up on a section of track. My son was watching a video on the TV not 3 feet away from the car and there were NO lines of static or interference on the screen, yet I could see arcing around the commutator.

So no EMI on a bare motor there then


Mark.
 

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Julius Wilkko
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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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Brian Ferguson
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Difflock, EMI interference may or may not directly affect other equipment, as Julius said, since many devices now filter it very effectively. Then again, even if it doesn't affect you, it may be driving your neighbour crazy! The RF interference is fairly short-range, but EMI interference sent back through the power line can reach much further. Good, regulated power supplies will block this inherently in their design, but poor supplies, like those furnished with typical race sets, can transfer interference right out into the mains supply and this can affect neighbours who are fed from the same mains supply and who may not have TVs, etc, that are quite as up-to-date or as effective at filtering. I have never experienced the problem myself, but many years ago I drove my neighbour crazy every time I had a club race at my house. That was okay, though, because he never figured it out and we didn't really get along well anyway.


Relax, though, I think the EMI police are still scouring the grounds around Inte's place - something about finding small chokes and capacitors outside a window...
 

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I have a problem with a couple of cars that play havoc with the scoring system on my track. The only solution so far had to move the computer and cabling to get as far away from the track. Anyone have a link of what I would need to buy in an effort to tame these cars down so I can return the computer back to its normal spot?
 

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Hi jhat

Please give more information about your set up. As a starter .........analogue or digital cars? What brand? What scoring system? If it's only a couple of cars that cause the problem, and other cars don't what's different about the cars?

That would help narrow down what the problem might be.
 

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Rich Dumas
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All of the 1/32nd scale motors that I have taken apart at least have a ferrite disc attached to the commutator, even if they have no external RFI filters. Scalextric cars add a small capacitor in parallel with the motor and Carrera cars have both inductors and capacitors attached to the outside of the motor. If your problem is actually sparking from the cars pickup braids the RFI filters on the car's motor may not solve the interference problem. You might want to turn down your room lights and see if the offending cars are sparking. A simple brush adjustment may solve your problem.

I have heard of counting/timing systems that had problems with interference. You indicate that you have a computer based system, but you have not indicated which one you are using. My own track uses Trackmate and that includes RFI filters. Trackmate is a very popular system in the US and I have not seen any reports of interference with that. A number of people have reported problems with homebrewed systems. Possibly you could get some of the capacitors that are used with Scalextric motors and put one across each pair of leads as close to the computer end as possible.
 

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If there isn't a 100n cap across the motor terminals you could put one there (ceramic disc should be ok, most have a high voltage rating) Or 47n (0.047uF) might be worth trying. cheap to try.

Extra cap from each terminal to the motor can might help. Its cheap enough to try so why not.
 

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Rich Dumas
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I forgot that the motor leads from a Scalextric car also go through a ferrite choke. Things like USB computer cables also have a choke in many cases. It would not hurt to include chokes for the wires that go to your computer besides the capacitors that I mentioned.
 

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Cars for digital systems normally have and need better EMI suppression than is necessary for analogue.

Lots analogue clubs have computer race control systems which run trouble free even using cars with no suppression at all.

All of the 1/32nd scale motors that I have taken apart at least have a ferrite disc attached to the commutator, even if they have no external RFI filters.
Agreed many motor do have those discs, they are particularly common on home set motors. However, there are plenty of slot car motors used in (analogue) 1/32 and other scales that don't have these discs, this is absolutely no problem with the computer race control systems used at many clubs.
 

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I recently aquired a crash landed drone which had 4 slim can type motors (FF050) similar to those in RTR cars. Each motor had a PCB on the brush end with a "delta" capacitor network, ie 100nF across motor terminals and one each from motor terminal to motor case. I would say about the maximum you would need for a similar slot car motor, we always used 5nF across our motors back in the day. The main problem is VHF interference on especially (old) TV's and stereo analogue radio. Digital systems are more tolerant except in poor signal areas, they can be disturbed by a passing car with poor HT leads, had this problem til I upgraded the TV antenna.

Inductors in series with the motor indicate a possible problem with the motor fitted to the car, the manufacturer has decided to provide a belt and braces approach to obviate any local problems. As someone commented earlier re cheap slot cars from China, I stripped out a motor from a cheap RC car and it also had the full inductor and capacitor network attached.

When I tried to buy a new suppressor for a small AC motor from the local Singer shop, the owner told me to throw the old one away and not bother! You cannot get definitive answers so I would advise everyone to at least add a capacitor across the motor terminals...
 
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