Suppressors when using 2.4gHz?

[geconParticipant @gecon]

Is it correct that motor interference supressors are not needed on brushed motors when using 2.4ghz R/C?

George

[geconParticipant @gecon]

[Richard SimpsonParticipant @richardsimpson88330]

I suspect that what you have heard is that the capacitors, which as you say are there to prevent interference generated by the motor, may not be needed if the communications between the transmitter and the receiver is significantly more robust and reliable when you are using 2.4Ghz.

Whether any interference from the motor has the potential to affect any other electronics would depend on the specific installation but I suspect that capacitors may frequently not be of any value any more. There may however be the odd occasion when the motor could still affect other on board electronic items, particularly if the commutator or brushes are not in the best of conditions and are arcing a lot.

[geconParticipant @gecon]

Many thanks Richard,

George

[ashley needhamParticipant @ashleyneedham69188]

Yes is the answer as Richard insinuates! In theory suppressors not needed.

Ashley

[Keith LongParticipant @keithlong89920]

Hi George

From experience, yes you should fit suppressors to the motor. I tried out an rc car without suppressors and the steering kept glitching at random. Two small capacitors fitted, one from each brush connection to the can cured it, but for the sake of completeness fit a third across the brushes as well.

[Richard SimpsonParticipant @richardsimpson88330]

That'll be one of the odd occasions I mentioned above Keith!

When you think about it, you are not going to do any harm by fitting them.

[geconParticipant @gecon]

I have them in stock, for once. I'll fit all 3! Though I think they're fidly things to solder. I have them on the Fisher drive motor and Bow thruster.

Be wielding the soldering iron over the kitchen table tomorrow, always popular with the Admiralty.

Thanks again to all,

George

[Malcolm FraryParticipant @malcolmfrary95515]

While the radio will not pick up any interference through its aerial, it will quite happily be affected by any stray voltages offered via the power. All RC depends implicitly on stable voltages to drive the voltage comparators that everything uses to get the timing pules right. A capacitor across the motor terminals will soak that source up nicely, I remain to be convinced that the other two do anything in practice as opposed to theory.

An unsuppressed motor is unlikely to generate radio frequency that will upset 2G4 radios. On the other hand, there is the outside chance that a model cheerfully transmitting motor noise might sail near to one running 27MHz, and provide a viable signal for that. The result, seeing that steering is invariably on channel 1, would be poor steering on the 27MHz boat. (Might be true of some 40MHz as well). So suppression is also good manners.

[ashley needhamParticipant @ashleyneedham69188]

Malcolm has a good point re other users.

Perhaps I have been lucky as The few times I have ever had a glitching issue, a simple cap across the terminals fixed it.

Ashley

[geconParticipant @gecon]

It does not happen often, but I'll be be 'suppressed' by saturday afternoon!

George

[HaigParticipant @haig]

What I have noticed is that Brushless motor do not require any suppression. I am going to replace the main drive motor in one of my submarines (using 29MHz radio) as it has suffered from interference from time to time.

[Richard SimpsonParticipant @richardsimpson88330]

I've always believed that the majority of the generated interference comes from the arcing at the contact face between the brushes and the commutator. A good way of reducing it is to clean and dress up the ends of the brushes and clean out the muck that collects in the commutator gaps. Some people use a very fine wet or dry paper between the end of the brush and the commutator to ensure the best possible fit at the contact surface. The gaps in the commutator have to be cleaned out with a pointed tool that is not going to damage the edges of the segments such as a cocktail stick.

Obviously a brushless motor does away with this and uses nothing more than a rotating magnetic field to turn the shaft so should generate very little interference.

[Malcolm FraryParticipant @malcolmfrary95515]

As a brushed motor rotates, each brush shorts out one of the windings as it passes from one segment of the commutator to the next. All of the energy stored in that bit of the armature wants to go somewhere, and that puts a lot of current through the bit of brush doing the shorting. The suddenly changing field that this causes also appears as stray voltage spikes at the motor terminals which send current p the motor leads. It is this current that generates the interfering signal rather than the spark itself, the spark is a visible thing that indicates that something is happening.

Bits of muck and uneven-ness on the commutator allow the sparking to continue for more of the rotation time, thus a tired motor (or one that was designed tired) generates more interference.

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