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Old 2015.03.18, 07:14 AM   #31
Jshwaa
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Originally Posted by byebye View Post
The caps reduce noise traveling up and off the motor wires. This causes interference. I don't believe the 2.4 ghz boards are affected by this because of the caps in between the positive and negative contacts on the board. . I can only speculate that PN doesn't include them on their motors because they know this already seeing as they've made they're own 2.4 board...
This is true too. If you are next to sensitive equipment (AM radio), you may hear a click in the audio if your motor is close enough to the antenna. May even hear a high-pitch whine kind of like a poorly installed car stereo where you can hear the alternator through the audio.

As a matter of fact, this 'back EMF' produced by the motor is causing problems with my dynamometer project. I am experiencing the main CPU reset itself in the even that I coil the motor wiring and place that coil close to the wiring to the tachometer input. The tachometer wiring is coupling in the noise and delivering it right to an input on the CPU board. The spike interferes with VCC of the CPU and actually disrupts the supply, and induces a power cycle effect like turning the power switch off then on really fast.

I will need to be careful how I route the power cabling with respect to the tachometer cabling to prevent this. It's amazing how much noise motors can produce.

The motor caps 'could possibly' be just a hoop that Kyosho had to jump through to satisfy the FCC too, because any electronic device has to conform to rules to ensure that it only can produce a certain level of interference to other electronic devices. Without the caps, the mini-z may float into a category of interference that would make it illegal to mass produce.

Just a couple other ideas about the motor caps...
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Old 2015.03.18, 10:25 AM   #32
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Question, why are the caps on the motor and not on the board? Do they need to be a close as possible to the source of the noise?
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Old 2015.03.18, 02:09 PM   #33
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Question, why are the caps on the motor and not on the board? Do they need to be a close as possible to the source of the noise?
Yes to the second question.
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Old 2015.03.18, 03:20 PM   #34
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Yes to the second question.
Wouldn't they also need to vary their capacitance to account for minor differences in the motors that change the noise put out by said motor? I can't imagine the PN 70ts I'm using in my tank put out the same level or type of RFI that the stock Kyosho motor does, that a bog-standard Maibuchi 130 from the 50 cent bin does, that a 20t bonkers bonneville special motor would.
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Old 2015.03.18, 05:45 PM   #35
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Wouldn't they also need to vary their capacitance to account for minor differences in the motors that change the noise put out by said motor? I can't imagine the PN 70ts I'm using in my tank put out the same level or type of RFI that the stock Kyosho motor does, that a bog-standard Maibuchi 130 from the 50 cent bin does, that a 20t bonkers bonneville special motor would.
The EMF is at the frequency of the motor's rotation, so you should not see a difference in the 'frequency' of the noise if any two motors were running at the same speed, no matter what the differences in the motor's composition may be. However, I did notice a ringing effect with the motor without caps that did not seem to exist with a capped motor. These harmonics(like octaves on a piano) occur at multiples of the main fundamental frequency, and could reach frequencies and amplitudes that could disrupt nearby electronic devices.

I'm starting to lean on this as being the main reason for the caps in the first place. It is easy for all of us to assume that it is to protect the mini-z, when it could in fact be to protect everything else 'from' the mini-z. Anything that relies on a consistent clock cycle that is within the same frequency as one of the EMF spikes could get jammed and cause a failed transmission or an audible click, or in some cases a resetting of a microcontroller.

At any rate, as long as you have a cap value that produces the filtration needed for all frequencies that correspond to an entire motor's range of rotational velocity, that cap value should be good for any other motor that operates within that same band of velocities, as all of the fundamental frequencies produced by the motor's should be within the same range.

It would take some pretty extensive theory testing to nail down the exact values that would optimize the filtration of each and every singular motor, which isn't worth it in my opinion. I usually wait until noise is a problem, and try to filter until it isn't. The motor spikes have not caused any issue with the operation of my mini-z, but they are causing issues with some of my other devices....
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Old 2015.03.18, 06:55 PM   #36
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I think the simple answer is that they are not strictly required with a 2.4 GHz car but you're still better off with them.
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Old 2015.03.19, 07:12 PM   #37
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So here's a little experiment I did with my scope and a motor with caps and motor without. Yea, I know it's not apples to apples if it's not the same motor, but bear with me... the cap effect is still obvious...

If I grab a wire with my scope probe and hold it just above the motor, I can get a view of the electric field produced by the motor.



Here's the same motor, and a view of the amplitude of the electric field vs. time at the wire above that motor.



Here's a 'different' motor, which does 'not' have caps...



And then here's a snapshot of the scope screens of each motor, with the amplitude jacked up a little bit on each so the harmonic spikes are a little more clear...

With caps...


Without caps...


If the caps would allow for easy access to the armature, I wouldn't have a problem with having them for cleaning out that noise, but as long as that noise is not causing my mini-z any harm, and I want to work on my motor, the caps are going to have to go...
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Old 2015.03.19, 08:11 PM   #38
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Originally Posted by Jshwaa View Post
If the caps would allow for easy access to the armature, I wouldn't have a problem with having them for cleaning out that noise, but as long as that noise is not causing my mini-z any harm, and I want to work on my motor, the caps are going to have to go...
I really don't understand this statement (that you've made a couple times)...you have all this techy motor BS and take the time to show us different "noise" graphs but you find that caps are impeding you working on your motor? Is de-soldering one connection point on each side that difficult or time consuming?

very cool info....totally beyond what's needed to discuss the thread but gotta love them props.
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Old 2015.03.19, 11:17 PM   #39
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I really don't understand this statement (that you've made a couple times)...you have all this techy motor BS and take the time to show us different "noise" graphs but you find that caps are impeding you working on your motor? Is de-soldering one connection point on each side that difficult or time consuming?

very cool info....totally beyond what's needed to discuss the thread but gotta love them props.
Yea, well, whatever... Thanks, I guess. Now to get this scope, 'er meter, 'er power supply to desolder caps for me... pfff...
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Old 2015.03.20, 02:29 PM   #40
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i for one love seeing the science behind the technology it's over my head but love pouring over all the tech talk, pictures, diagrams, etc.
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Old 2015.03.20, 03:20 PM   #41
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I appreciate your time to connect up the scope and attempt to see what is going on but I am not sure how valid it is. A floating scope probe rarely gives any kind of result you can trust. I think a much better test would be to connect the scope probes properly to the motor terminals and then look at the AC signals that are being generated. If you want to look at the true spectral(RF) noise that is being generated then you need to use a proper tool for that - a spectrum analyzer.
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Old 2015.03.20, 07:27 PM   #42
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TheSteve, I understand your thought process with that...'no circuit without the ground connection', right? Well that is how electro-magnetic fields work. The magnetic field produces an electric field, where the potential is still there because it is disrupting the normal state around it. It can exist because it is periodic, with periods that are very small, but can have magnitudes that can be relatively high.

As far as the validity of the test, well that would be more apparent with a video, as you can see the amplitude of the periodic signal go up and down in proportion to the distance the wire was from the motor. The wire is acting like an antenna, picking up the electric field from the motor, just as a radio would pick up the signal from a radio station. Of course as you get closer to the radio station, your reception improves, just as the wire does in picking up noise by being closer to the motor.

And by the way...Thanks to all of you that can read one of my posts and either take it or leave it. I like the opportunity to use the public domain to not only share what I've learned over the years, but to reaffirm it for myself. Integrating something you've learned is important, otherwise the knowledge is useless. I'll try not to fill up the internet in the process, and hopefully I can get by some of the funny particulars of the natives in the process...
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Old 2015.03.20, 08:59 PM   #43
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Originally Posted by Jshwaa View Post
TheSteve, I understand your thought process with that...'no circuit without the ground connection', right? Well that is how electro-magnetic fields work. The magnetic field produces an electric field, where the potential is still there because it is disrupting the normal state around it. It can exist because it is periodic, with periods that are very small, but can have magnitudes that can be relatively high.

As far as the validity of the test, well that would be more apparent with a video, as you can see the amplitude of the periodic signal go up and down in proportion to the distance the wire was from the motor. The wire is acting like an antenna, picking up the electric field from the motor, just as a radio would pick up the signal from a radio station. Of course as you get closer to the radio station, your reception improves, just as the wire does in picking up noise by being closer to the motor.

And by the way...Thanks to all of you that can read one of my posts and either take it or leave it. I like the opportunity to use the public domain to not only share what I've learned over the years, but to reaffirm it for myself. Integrating something you've learned is important, otherwise the knowledge is useless. I'll try not to fill up the internet in the process, and hopefully I can get by some of the funny particulars of the natives in the process...
Yes, I know exactly how electromagnetic fields work. Believe it or not you're not the only one here that might be educated.
Anyway, you clearly have no interest in learning from others, only saying what you think you already know.
There are lots of people here that do appreciate you sharing your knowledge but you may also want to realize you might also be able to learn something.
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Old 2015.03.20, 09:14 PM   #44
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yes, i know exactly how electromagnetic fields work. Believe it or not you're not the only one here that might be educated.
Anyway, you clearly have no interest in learning from others, only saying what you think you already know.
There are lots of people here that do appreciate you sharing your knowledge but you may also want to realize you might also be able to learn something.
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Old 2015.03.20, 10:40 PM   #45
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Yes, I know exactly how electromagnetic fields work. Believe it or not you're not the only one here that might be educated.
Anyway, you clearly have no interest in learning from others, only saying what you think you already know.
There are lots of people here that do appreciate you sharing your knowledge but you may also want to realize you might also be able to learn something.
Well, my apologies. I was trying to have a discussion with 'you' and address something 'else' at the same time and it came out bad. However, in your effort to challenge the validity of an experiment I would have thought you might want to back up your stance on that. Regardless of our educations, if the pictures aren't proof enough of what I'm saying is true, do you expect me to concede to a couple of your sentences of mere nay-say? By all means Steve, suggest something to me that could further bring us closer to an understanding. I love learning. However if all you got is your thumbing of your nose at ideas, I don't know what else you want from me.
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