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[Shellback]

Can any of you masters of the arcane mysteries enlighten me? I have three questions: 1 are there purpose-built electrical connectors for the two brass posts on the Marx Monoperm motors, 2 are they at the same potential as the two tags on the sides of the motor body and 3 do I have to make a positive soldered connection to the body of the motor? The motor has never been used and offers no clues as to these questions. I don’t want to remove the paint from the body if it is not necessary, inviting rust.

[Colin Bishop]

It is all explained here:

https://www.modelboatmayhem.co.uk/forum/index.php?topic=54053.0

Read carefully as there is a mixup with the photos

The tags go to the brushes. I must admit I have always soldered to the brass pins!

Colin

[HMS Invisible]

Can any of you masters of the arcane mysteries enlighten me? I have three questions: 1 are there purpose-built electrical connectors for the two brass posts on the Marx Monoperm motors, 2 are they at the same potential as the two tags on the sides of the motor body and 3 do I have to make a positive soldered connection to the body of the motor? The motor has never been used and offers no clues as to these questions. I don’t want to remove the paint from the body if it is not necessary, inviting rust.

Q 1 & 2 is answered after reading the five year old thread

Q3
It will work without suppression on 2.4 GHz.
 If you are using 27 or 40MHz FM or AM sets:- a single 10nF to 47nF Y5V (mind the rated voltage) ceramic disc capacitor, coloured brown ,across the motor, is enough.
 You won't notice a difference by soldering the two capacitors to the case.

[Shellback]

Thank you both, you’ve dispelled the fog and set my mind at ease.

[roycv]

Hi I use these motors for my smaller model boats.  Recently I did have an interference issue at quite moderate range,  After checking for the obvious I soldered another 20nf capacitor from each terminal on the motor, to the body of the motor and the range problem was cured.
I had to file a little of the grey paint finish off to get to bare metal and tinned and soldered it quickly then I had a solder point to solder the caps' on to.
I use the tiny esc's that have the Rx type wiring and connectors on, I use 7.2 volt Nimh batteries.  They are only a few pounds and work well.  (30mm x 16mm x 8mm high).
regards
Roy

[HMS Invisible]

If Shellback had the possibility of common mode interference, I would have advised "You don't need to solder to the case if you fit one of these filters or the clamp on type".
If it wasn't not, I'd say try soldering again and with a different capacitor.
 

[Shellback]

Just when I thought it was safe to go back on the water...


To put my query in some context, I am resurrecting a project I started about 30 years ago. Caldercraft Northlight Clyde Puffer; I abandoned it due to family pressures and the fact that the (second) hull was so distorted that I despaired of ever correcting it. I had intended to re-use the 4.7Mh kit I'd had in a R/C aircraft but my son very kindly gave me a Carson entry-level kit for my 80th birthday - last week, as it happens. I want to use the Monoperm motor from my first attempt, not appropriate for an aircraft but waiting patiently in the wings (no pun left unturned).


I am currently wresting the hull moulding into shape - I feel like a lady's maid from a costume drama: tighten the corset strings here, let them out there - and have not run the motor except for a brief burst to see if it worked and to check direction of rotation.  It does and clockwise. I am prepping the project slowly, step by step, filling and filing as I go.


You will see that I am therefore not actually experiencing interference  problems but wish to avoid them, having been terrified by tales of exploding ESCs had the correct number of capacitors and ferrite toroids not been installed in the correct places. microgyros' comment about common mode interference went straight over my head and might have been in Swahili; but that is to illustrate my ignorance, not to disparage his comment. The suppression kit from Mtroniks - three brown cs and a helpful diagram - seems to chime with roycv's answer and, indeed, sundry others. If that will prevent a meltdown in the ESC dept should there be a R/F burp from the motor, I'm well satisfied. If any o' youse is itherwise mindit, I'd be happy to hear your thoughts. I have plenty of time before I launch M'Lady Northlight. Hey, there's a name!

[Colin Bishop]

Yes, no point in overthinking this. Just connect the motor up and probably you only need to fit the one capacitor across the pins or brushes just in case. I never had any problems with Monoperms back when I was using them with 27meg gear and my Dean's Medea kit uses a Monoperm with the same setup under 2.4Ghz. Never had a problem. They draw so little current anyway so there's no massive sparking going on.

Re wrestling the hull back into shape, use a hairdryer to warm it up, hold it the desired position and when it cools it should set in the new position. You don't need to melt it, a hair dryer is fine.

Colin

[HMS Invisible]

... microgyros' comment about common mode interference went straight over my head and might have been in Swahili; but that is to illustrate my ignorance, not to disparage his comment.

Two capacitors to the case and the ring core are both to suppress common mode interference, but the latter fits your requirement:-
I don’t want to remove the paint from the body if it is not necessary.
But it isn't going to be a problem so you just need a single cap between the brushes and therefore you won't notice any difference by soldering the other two

The suppression kit from Mtroniks - three brown cs and a helpful diagram - seems to chime with roycv's answer and, indeed, sundry others. If that will prevent a meltdown in the ESC dept should there be a R/F burp from the motor, I'm well satisfied.

I don't speak for Roy but he soldered the two to the case and his range problem was cured. It doesn't contradict my first post.
My follow up suggestion with an alternative to the additional two caps doesn't address why the additional to caps cured Roy's problem.
The capacitors won't protect your esc from an rf induced meltdown but you don't need to worry about that either.

If any o' youse is itherwise mindit, I'd be happy to hear your thoughts. I have plenty of time before I launch M'Lady Northlight. Hey, there's a name!

A resettable polyswitch, rated to trip if the motor stalls, will protect the motor. The resulting current alone would not tax the ESC enough to meltdown unless you preheated the drive transistors with extra wattage from a linear bec at 12 volt input. Again, that possibility is avoidable with the right measures.

[Shellback]

I am overwhelmed by the depth and breadth of the knowledge on this wonderful website. And by the generosity from the members: thank you all. I think I have extracted the information I need to avoid disaster and will report back later. I’m taking photos as I go and might submit a build log when all is done. Could be of help to other strugglers in the fog, a fog blog?


Roy, I knew of the hairdryer technique and had employed it in the original build without any success. As it happens, I had another go last night, as ever was. Lo, behold and cor blimey, it worked. No more do my bulwarks bulge.


Thanks to you all: I’m off to the workshop.

[Shellback]

Sorry, I addressed my hairdryer comments to Roy - it should have been Colin. Senior moment.

[roycv]

hi microgyros, the ferrite ring you suggest, how many turns would you recommend?

I have been using RC for 55 years now and 95% of the time I use electric motors and it used to be enough to put a 0.1 micrfarad across the terminals.  I still use the same type motors but find I have been increasing the amount of anti-interference needed.  I am still using 27 and 40 Mhtz RC.

I hear but do not know that the 2.4 Ghtz RC do not need the same interference measures with electric motors.  I wonder if modern esc's which is the only change, have less anti interference.  Not being privvy to the circuit diagrams it is difficult to know.
I used to make my own esc's but they are so cheap now it is not worth the effort.
Regards
Roy

[malcolmfrary]

Hi I use these motors for my smaller model boats.  Recently I did have an interference issue at quite moderate range,  After checking for the obvious I soldered another 20nf capacitor from each terminal on the motor, to the body of the motor and the range problem was cured.
I had to file a little of the grey paint finish off to get to bare metal and tinned and soldered it quickly then I had a solder point to solder the caps' on to.
I use the tiny esc's that have the Rx type wiring and connectors on, I use 7.2 volt Nimh batteries.  They are only a few pounds and work well.  (30mm x 16mm x 8mm high).
regards
Roy

The only problem with low value capacitors used for RF suppression is that if one grows an internal broken wire, there is no easy way to test it using commonly available test gear.  Adding another in parallel, or two in series across the motor terminals with a mid point attached to the case effectively replaces the broken wire with a bypass.  I tend to the view that "the simpler, the better", more components is just a way of increasing the chances of the cure being worse than the problem.  The single capacitor has always done fine for me, but to prevent the capacitor legs acting as transmitter aerials I try to ensure that they are as short as possible and the same length.
If there are any worries about rust following soldering to the can, it can always be painted over afterwards, but I've never felt the need to go that far.  I've yet to come across an ESC that could be damaged by too much suppression capacitance, especially at the low power levels involved in this case.  Getting to that kind of value with capacitors with a suitable RF rating would probably physically overload the boat.
Well behaved motors like Marxs' offerings probably don't need suppression when used with 2G4 radios, but it might be considered good manners just in case they get used in company with others who are still running, say, 27MHz.
When I was trying to keep radio hams out of telephones, the rule was "as many turns as you can fit in a single layer, but leave a gap between the ends".  I was using the phones cord, so the two wires were together, but if using single wires, check that the turn directions match.  You don't want to accidentally make a ferrite receiver aerial.
Radio interference is usually taken to mean an unwanted signal generated locally and picked up by the receiver aerial, then processed by the receiver to give an unwanted output.  But if the source is strong enough, an interfering signal "might" be picked up by other wiring.  The semiconductors in the output stages of some electronic gear were quite capable of acting as crystal detectors, and providing themselves with enough signal to switch unexpectedly.  I would not expect this to be a problem with the power levels involved with a Puffer and a Monoperm, especially with a sensible wiring layout.

[Shellback]

Thank you for your help Malcolm. I am tending to agree with you that "the simpler the better". I was concerned by tales of catastrophic ESC damage due to poorly suppressed motors but, reading all the contributions from Forum members, the worst case would seem to be that I might annoy a 27MHz user nearby. I am not a member of a club and, given the current restrictions, am not likely to be sailing in company any time soon. So: one 0.1μf cap, short legs, soldered between the motor terminals is the way I'm going to go. In fact, that's the way I've gone.

[roycv]

Hi micro...  thanks for the detailed response.  With winding the ferrite same direction turns for both winds?  Does it have to be a ring or would a length of ferrite also work?

The intereference I have had has always been the slight chattering of the motor, or interruption of the signal, usually as the range increases.  Seems true for the simple esc's which amplified the M / S ratio as received and the higher frequency 'cheap' ones now.

I used to make up the Electronize ones when he used to supply them as kits.  Everything has gone too small for me now.

Regards
Roy

[HMS Invisible]

Thanks in advance, maybe? That was Malcolm. It covered the important part about winding direction.

Look at the Electronize instructions for the WIRING paragraph.
In other words:  "don't do as the very first image" Link because, at best, one esc superimposes noise onto the clean esc input signal of the others (top of esc_signal_noise.jpg) to make the middle trace when you throttle (bottom rectangular trace)
At worst, if a rusty connection is in a wiring loom negative (or very long supply wires ) it can send the full motor current to the battery -ve through, and fuses, the back door route to the battery via the internal esc common connection points & 22 gauge black cables.

In that application the common mode filter is one of a few fixes and can be easier done with a servo lead threaded through a core. It is low frequency, not RF, so you need high permeability (high μ) ferrite.

I've suggested in other threads, where they had FM/AM radio & RF interference & no suppressor fitted or to hand, that any old desoldered capacitor from scrap would suffice.

55 years means you missed (by a quite a few years) main frame computer lab simulation packages for high frequency response & component stress for complex circuits. There are online tools, and freebies, to do that stuff/chore now.
It is easy enough to remember, at high frequency, inductive and capacitive reactance predominates so circuit & component analysis requires the more accurate RLC model for every component and for circuit board layout and any cables.

The high MHz frequency model for a common-mode filter would include the air dielectric & capacitance between adjacent transformer turns and so why you keep them apart.
What is crucial is creating a mirror image with the same 1:1 ratio and the winding direction.
It makes a transformer that impedes unbalanced current in the two wires so, no, a wound solenoid will not work.
The mutual inductance value is not important & number of turns matters only as they are limited by space.
Saturation won't happen so you can use high μ ferrite material as you have two balanced windings. If you dismantle an old server, the single ended chokes will be low permeability and, easily identifiable from the two windings, the 1:1 common mode and clamp on ferrite will be high μ.

2.4 GHz and suppression

Just look up the internet for frequency response plots for capacitors for that subject. (Search Link)
Perhaps it stirs up memories of textbook & chalk board diagrams. The wire ended & high value caps are inductive have passed through self-resonance long before 2.4 GHz is reached. It then becomes clear (or refreshes the memory) the reason for a low value capacitor (for high frequency decoupling) in parallel with a higher value capacitor.

I used to make my own esc's too before a mistery illness & life events got in the way of the fun in recent years.
I'll get back to doing it when, and if, I can.

[roycv]

Hello Micr.o.. and Malcolm your advice in information always welcome.  I have read through the advice and even remembered some of it!

Back in the day I was a mainframe 'engineer', but we did everything from replacing gears in gear boxes and re-drilling and reeming taper pins and adjusting Geneva intermittent drives through to other mechanical, electro mechanical, relay martices, printing mechanisms, hydraulic driven disc drives optical control of 2400 feet tape decks and even an early cheque sorter using an analogue computer to read the magnetic ink.  That was apart from the fast progession of processor models and speed and their s/w.

I preferred to mend my own PCB's as the float of 'repaired' ones was highly suspect, including the early transistor ECL and CCL technology.  Having left behind valves and the like.  One of the things you learn along the way is a logical process of thinking.

You name I've worked on it, I am glad I was there at the time and would not have missed it for anything.
The Eureka moment came one evening when I was called to a site doing calculations for stressing a Thames Bridge and it was churning out wrong numbers.
The processor had an extended mathematical unit (EMU) attached, I had to press a button and get an 18 line printout.  I then found the reference book which the numbers referred to and worked my way through.  It told me to change the pcb in location XXXX and it all worked.

 I did not know what the fault was nor what the cure was.  The end is now very nigh for me and my ilk!
I got the message though, I applied for and got a management job and 'guided' others in their tasks.

The last big job (for the company) was to find a problem with a small electric motor that should have had a ballrace instead of a plain bearing.  I worked out that the savings to the company over 2 years paid all of the salary I had ever been paid. 

I do like small electric motors!

regards
Roy

[HMS Invisible]

Hi Shellback,
555 motors have an internal ferrite suppressor. 

Some links that explain the alphanumeric capacitor codes X7R, Z5U, Y5V mean.You can then forget it all and, like I suggest, fit one cap that is salvage from scrap, isn't a short circuit, and looks right. https://www.allaboutcircuits.com/technical-articles/x7r-x5r-c0g...-a-concise-guide-to-ceramic-capacitor-types/
https://ec.kemet.com/blog/mlcc-dielectric-differences/

Roy, I'm 56. The museum artefacts disappeared before I was a student.     

The early kits you soldered together would be ZN409 based so don't you think they'd go better with glitch free 2.4GHz sets?

I've not tried the kemet simulator.The "K" magnutude graph shows 2.4GHz is in another universe.
https://ksim3.kemet.com/capacitor-simulation

[Shellback]

Hello micro, While I appreciate your efforts I don’t think I would ever apply the knowledge you are working so hard to impart, even if I understood the smallest fraction of it. Your second sentence is the one I latch on to and I shall go directly to that, not passing go and giving a total body swerve to sentence one and the alphanumeric entities alluded to therein. If I can shoehorn a battery, receiver, ESC, motor and sundry servos into the boat’s hull sufficient to drive it through the water at a reasonable pace without bursting into flames - the boat, not me... although... - I shall consider the job a good ‘un and be mightily pleased.


Colin’s article on motor, prop etc. selection could not have come at a better time.


Oh what a wonderful resource is Model Boat Mayhem and how well named. Power to all your elbows. The elbows of all. I’ll stop now. 

[roycv]

Hi Micro.. I know where you are coming from re 2.4G sets but I have so many 27 and 40 Mhtz sets that there is no incentive.  I have more 5 ch 40 Mhtz rx's still looking for models than I shall ever build. 
Last count was 20+ tx's.  My caps I buy in 50's from Farnell solve any interference problems so I have glitch free model boat and yacht outings.
The only complication is the 4 types of crystals but I have lots and they are still on sale.  I work on the principle if it works then why replace it.  However this is not something my wife shares and as we have been together for over 57 years we learn to compromise!

regards
Roy

[HMS Invisible]

Hi Micro.. I know where you are coming from re 2.4G sets but I have so many 27 and 40 Mhtz sets that there is no incentive.  I have more 5 ch 40 Mhtz rx's still looking for models than I shall ever build. 
Last count was 20+ tx's.  My caps I buy in 50's from Farnell solve any interference problems so I have glitch free model boat and yacht outings.
The only complication is the 4 types of crystals but I have lots and they are still on sale.  I work on the principle if it works then why replace it.  However this is not something my wife shares and as we have been together for over 57 years we learn to compromise!

regards
Roy

Roy, just to let you know, are you aware of the ongoing discussion about the availability for model submariners and the plus and minus points of the alternative?
I have half the number of your 40FM hoard so I don't keep track of all the individual threads but this is a short one: Modifying an old TX for openLRS at 458MHz