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Author Topic: Model Boat wiring  (Read 76197 times)

Z750Jay

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Re: Model Boat wiring
« Reply #25 on: August 11, 2014, 11:01:50 am »

I tend to go with three to cut down on the RF, not sure why it's but it's what he electronics guri told me to do. Probably as that gives each one a connection to the casing and the other thus suppressing the RF interference
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inertia

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Re: Model Boat wiring
« Reply #26 on: August 11, 2014, 11:15:47 am »

The article "Beat RFI" (March 2006) here explains just about everything you need to know. The capacitors are to reduce both current spikes in the power supply wiring and the radiated RFI from the motor itself. Like the mans says, just do it.
http://www.modelsoundsinc.com/articles.php
DM
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Z750Jay

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Re: Model Boat wiring
« Reply #27 on: August 11, 2014, 11:24:47 am »

Great article and reading it did give me a face palm moment - earthing via the stuffing box. Considering one of last weeks jobs was checking the earthing points on a minesweeper why did I not think to include this on a model boat?
I am not sure how effective it would be but it has got me thinking
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Bob K

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Re: Model Boat wiring
« Reply #28 on: August 11, 2014, 11:57:15 am »

That article was very illuminating.  Many thanks Dave M.
Stresses the importance of wiring layout, keeping RF sensitive items such as Rx far away from RF sources (ie motor etc). Personally I tend to loom wiring in well separated groups, power, control, servos.
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david48

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Re: Model Boat wiring
« Reply #29 on: August 11, 2014, 12:08:55 pm »

Is earthing to to the shaft tube more to do with galvanic corrosion,than system earthing , I do not now that's why I ask .
David
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U-33

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Re: Model Boat wiring
« Reply #30 on: August 11, 2014, 12:13:39 pm »

Yep, I know there's no capacitors on the motor, I'll whip it out and solder a set across the terminals. I have a stack of Action ones stood standing by ready, so once the second set of painkillers have kicked in, that'll be the first job.


Cheers guys, and well spotted Mr M. ;D


Rich
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Z750Jay

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Re: Model Boat wiring
« Reply #31 on: August 11, 2014, 12:25:43 pm »

I don't think that galvanic corrosion is a big factor for us as our models don't spend that long in water and more to do with contact area to earth to bleed off those unwanted RF wiggles. A lump of aluminium would be better and would also act as a sacrificial anode for galvanic corrosion. Hmmmmm, not got a job on for this afternoon so the mind is going for a wonder
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inertia

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Re: Model Boat wiring
« Reply #32 on: August 11, 2014, 12:27:52 pm »

Cheers guys, and well spotted Mr M. ;D
:kiss:
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Buccaneer

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Re: Model Boat wiring
« Reply #33 on: August 11, 2014, 01:05:31 pm »

Please spare a thought for those of us that try but do not quite achieve. We are not all technically trained or knowledgeable. After a few years of wooden static boats (I can cope with wood) I moved into RC in 2006. A couple of years later I won Bronze at the Beijing Olympics in the 50 Metre 'Running Away from Soldering' event.

As time has passed I have slowly improved my use of the soldering iron, plastics, paint and Superglue but will never achieve the level of some of my friends at the pond.

Let us not forget:
1) There is a difference between lack of ability and laziness.
2) Don't say "All you need". This is on a par with giving the wife a lawnmower.
3) Don't say "It's easy" All things are once they are explained, you have been trained, and you find you can actually do it.
4) At the end of the day it's on the pond, it works and it's my pride and joy.

Encourage us and help us, but please don't put us down and put us off.

Buccaneer
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Plastic - RIP

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Re: Model Boat wiring
« Reply #34 on: August 11, 2014, 01:13:07 pm »

Is earthing to to the shaft tube more to do with galvanic corrosion,than system earthing , I do not now that's why I ask .
David

Earthing the shaft tube? That sounds like complete rubbish!

I'd love someone to convince me otherwise. Is the shaft a homo-polar generator?

Compared to a motor or PWM controller, anything else will be negligible.
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Z750Jay

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Re: Model Boat wiring
« Reply #35 on: August 11, 2014, 02:00:31 pm »

The RC plane lot never bother with RF reduction much beyond the motor and when their toys go wrong it gets real expensive  :-)
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inertia

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Re: Model Boat wiring
« Reply #36 on: August 11, 2014, 02:13:18 pm »

Please spare a thought for those of us that try but do not quite achieve.
Don't say "It's easy" All things are once they are explained, you have been trained, and you find you can actually do it.

Quite.
I've no problem with helping someone who genuinely wants or needs assistance and appreciates it when given. What does annoy me are those folk who dismiss the whole subject with some careless remark like "O, not electronics! It's so boring, and anyway my models work OK without me having a degree in rocket-science". These are generally the folk whose models are rescued most often or who spent most of their sailing sessions with the model on the bank with the top off. I've no time nor sympathy for them, and I don't have a degree in anything!

Plastic
I think you'll find the phrase was "earthing to the shaft tube", which makes a slight difference to your reply.

Jay
I don't think anyone is suggesting that much is necessary in the way of RF reduction beyond the motor because, as Plastic says, there's not much else which comes close as a source of it.

DM
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Z750Jay

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Re: Model Boat wiring
« Reply #37 on: August 11, 2014, 03:36:20 pm »

I wholeheatedly agree with you.  Even in the short time I have been in the hobby, most of the people that seem to suffer break downs treat electrics/electronics as a black art and take no care with what they do.
One chap kept frying his sail servos in his Dragonforce65 and put it down to bad servos. Had a look after the third one in as many weeks and rather than the usual 4 AAA packs of rechargerbles we were using he had used a 5 cell LiPo so he was powering his servos at around  7.3v.  Asked him why and he said "well more volts = more power but I don't know electrickery"
He is now using the same packs as the rest of us and his servos have stopped dying
Oh he was also runing a speed boat with the motoe and battery exposed and wondered why the motor was smoking a bit
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Z750Jay

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Re: Model Boat wiring
« Reply #38 on: August 11, 2014, 03:43:02 pm »

Even though I am an electrician by trade, I tend to deal with big AC wiggles 440v 3 phase stuff most of the time so some of the electronics is still a head scratcher for me.
How the digital 2.4 Ghz mutiplexed Tx/Rx stuff works I understand enough to know it makes electronics look easy!
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Plastic - RIP

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Re: Model Boat wiring
« Reply #39 on: August 11, 2014, 04:00:40 pm »

I've spent my working life playing with RF up to 30GHz at powers up to 100KW and solving EMC issues. I'm comfortable with motors and speed controllers interfering with radio equipment.

Fitting ferrites on leads, capacitors on motors, decently sized, short wiring runs and keeping the receiver as far away from the noise sources as possible will solve almost everything.

Earth-bonding to a prop tube? Why? This is not like a mains supply with lots of potential earth loops. There's not a link to anything else to develop a potential difference across.
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Z750Jay

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Re: Model Boat wiring
« Reply #40 on: August 11, 2014, 04:06:49 pm »

The earth bonding on the prop tube did get me.
I can see in theory why but like you said there is no real point as the prime sorce of RF is the motor and dodgy wiring.
The amount of intermitent faults we have at work that are down to bad connections is unreal.
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sparkey

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Re: Model Boat wiring
« Reply #41 on: August 11, 2014, 04:28:10 pm »

As Z750Jay says solid connections are the key to trouble free installations,usually you find that the guy who takes time and trouble over the look of the installation will have taken the trouble to make all of the connections sound,a moment spent going round checking the tightness of terminals can save hours looking for faults,Ray.
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Captain Povey

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Re: Model Boat wiring
« Reply #42 on: August 11, 2014, 04:55:36 pm »

 :-)) Yep Guilty as charged. I start out full of good intentions and then change my mind so much it all goes to pot. Please do not look in any of my boats if you are of a sensitive nature and allergic to spaghetti. Having said all that I think the termination points are pretty sound its just what goes on in between reflecting the thought process going on between my ears. {-) Graham.
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inertia

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Re: Model Boat wiring
« Reply #43 on: August 11, 2014, 05:05:55 pm »

Earth-bonding to a prop tube? Why? This is not like a mains supply with lots of potential earth loops. There's not a link to anything else to develop a potential difference across.

Might I suggest you take up the matter with David Harrison, the bloke wot wrote it? You'll find him very friendly and informative. You can contact him c/o Model Sounds Inc. I'd be curious to see his reply as this point has puzzled me for a while, but I didn't bother chasing it down because RFI doesn't figure on my personal list of problems.
Dave M
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Netleyned

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Re: Model Boat wiring
« Reply #44 on: August 11, 2014, 05:26:54 pm »

I wholeheatedly agree with you.  Even in the short time I have been in the hobbu, most of the people that seem to suffer break downs treat electrics/electronics as a black art and take no care with what they do.
One chap kept frying his sail servos in his Dragonforce65 and put it down to bad servos. Had a look after the third one in as many weeks and rather than the usual 4 AAA packs of rechargerbles we were using he had used a 5 cell LiPo so he was powering his servos at around  7.3v.  Asked him why and he said "well more volts = more power but I don't know electrickery"
He is now using the same packs as the rest of us and his servos have stopped dying
Oh he was also runing a speed boat with the motoe and battery exposed and wondered why the motor was smoking a bit
?

Five cell lipo is 18.8v.
 %% %%
Where did he stow it in a DF

Ned
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Z750Jay

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Re: Model Boat wiring
« Reply #45 on: August 11, 2014, 06:02:01 pm »

It was a wierd small one about the same size as a standard 5 AAA pack. Probably was a standard but with LiPo connections.
I was catching up with a mate who is a complete God with electronics(prototype, programming chips and one off electronic stuff business) and he said putting anything more than 6v through a servo is bad.
He is into his model railways and has developed servo based gates and signals with adjustable bounce and drop speeds so has some experience with them.
He will be helping me over the winter with some of strange things I want including a switchable power supply from remote

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Netleyned

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Re: Model Boat wiring
« Reply #46 on: August 11, 2014, 06:11:23 pm »

I use a five cell AAA in my DF velcro'd to the side if the fin box.
Not had any problems with the winch.
Had a rudder servo burn out nearly melted the hull but the
pond cooled it

Ned
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Z750Jay

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Re: Model Boat wiring
« Reply #47 on: August 11, 2014, 06:27:28 pm »

You have got to love those DFs.!
Thinking on it he may have been using 6 cell packs. I know it was one of those "WTF are you using" times.
They did not look "right". More like a battery pack from a fire and flood detection system on board.
Think it may of been something like this
http://www.modelboatmayhem.co.uk/forum/index.php?action=dlattach;topic=48201.0;attach=138963;image
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inertia

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Re: Model Boat wiring
« Reply #48 on: August 11, 2014, 06:54:44 pm »

I've just re-read that article again - this is the relevant bit:

Always ground the motor cans by connecting them to your propeller shaft stuffing box. If they are
not connected to anything other than the suppression capacitors, they will act as big fat antennas
radiating the RFI coupled into them by the capacitors! Exactly the opposite of what you want!
Also ground the negative battery supply lead so that you have ONE 0V or ground reference point.
Make sure the propeller end of the stuffing box has a small area without paint to make contact with
the pond water. Although the pond is not a great electrical conductor, it does act as a weak ground
plane, dissipating the motor can RFI signals to ground.


I suppose you could take issue with the last sentence but the rest makes sense. Doing something as simple as grounding two motors and a battery terminal (which may not actually be required) makes more sense than pretending you know nothing about electrics and leaving off suppressor caps - which does matter, and often quite a lot. Anyroad up, I've stood on this soapbox before and so it's time to climb down (again).
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Bob K

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Re: Model Boat wiring
« Reply #49 on: August 11, 2014, 09:49:33 pm »

In the three years I have been into RC boats I have learned so much from this forum, and this thread is a shining example.  Despite not having had an electrical breakdown in around 250 outings Dave's posting on good RF practice has added to my knowledge and ability to build ships that work as well as they (may) look.  We can all learn and improve our skills.

At almost every session there have been numerous breakdowns, almost all electrical in nature.  Rescue Tugs have become a necessary part of sailing days.

May I suggest that at regattas a prize may be offered for the most professional wiring job in order to promote good reliable electrical practice.  It could make my newly acquired Rescue Tug redundant ( tee hee !)
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