Suppressor thingies

[Dave MilbournParticipant @davemilbourn48782]

All will be revealed, Dr Dude.

[Colin BishopModerator @colinbishop34627]

But one last question…..what is wrong with choc-block connectors?

They taste horrid!

Colin

[Malcolm FraryParticipant @malcolmfrary95515]

Any screw connector is liable to work loose if used where vibration is possible. Thinking back to old type telephone cabinets that were full of the things. Firmly planted to the ground, traffic vibration could do the job. Or undo it, as it were.

With choc blocks, there is always the uncertainty of actually getting a solid metal to metal connection, and when it is got, it is open to air. In the case of model boats, damp air. Damp air plus dissimilar metals usually equals trouble sooner or later.

A minor point about fitting capacitors – the leads should be kept short and they must be mounted as close as possible to the motor terminals. Long leads to a capacitor can actually act as an aerial transmitting interference. Perhaps not much, but the motor is usually a lot nearer the RX aerial than the transmiitter.

[The Long BuildParticipant @thelongbuild]

Posted by Dave Milbourn on 27/09/2013 14:11:22:

O – I almost forgot the most common fault – not reading the instructions FIRST.

Reading the What !!

[Paul TParticipant @pault84577]

Its surprising how many people don't read instructions, specifications and drawings.

Dave

How do you get a good soldered connection to the can of a motor? (don't say all will be revealed)

[Dave MilbournParticipant @davemilbourn48782]

Use a small file to roughen and clean the case on the spot where you want the joint. Clean with IPA or meths (that's isopropyl alcohol – not India Pale Ale….)
Use at least a 25W iron with a 3mm bit or wider. (I have a 40W solder station).
Tin the iron then apply it to the case, feeding in solder to form a blob about the size of a small pea. Use resin-cored lead-based solder.
Bend and fit the two small caps to the motor terminals.
Bend the other legs of the suppressors to touch the solder bob.
Apply the iron and some more solder. Heat until the solder melts and "sucks" the wire legs into the blob.
Solder the other suppressor across the two terminals.
Done.

[Malcolm FraryParticipant @malcolmfrary95515]

What Dave said plus I find that a dab of flux on the area to be tinned helps a lot when soldering on big lumps of metal. That, and using a very hot, high powered iron to ensure that the job is done as quickly as possible and the iron removed before the plastic bits know you're there.

Most soldering problems come from not having the work pieces clean enough, using an iron that isn't quite up to the job, and not letting it reach its proper temperature.

[Bob Abell 2Participant @bobabell2]

It would be a great help if the motor manufactures provided small thin tabs on the motor casing

Otherwise, it`s out with the big daft copper soldering iron…..Which deters me no end!

Hence…….They don`t get fitted!

Bob

[Dave MilbournParticipant @davemilbourn48782]

Which deters me no end!

Why?

Dave M

[Bob Abell 2Participant @bobabell2]

It seems wrong to have to heat the casing up to such a high temp, just for a miserable bit of wire!

Tabs would solve the problem nicely….IMHO

I don't mind paying 25p for such a nice feature?

Bob

[Dave MilbournParticipant @davemilbourn48782]

No – you miss my point, Bob. Why does using a soldering iron deter you from fitting suppressors when no motor I know of has your tabs fitted? I doubt if Mr Mabuchi could be persuaded to alter his assembly lines just for a few old geezers who make toy boats, but I have his address in case you wish to write to him…………
If you are so wary of soldering then you could always drill and tap a small hole in the case (say M2.5); fit a screw and trap the wires between two washers – or use a solder tag. Just make sure all the swarf is removed from the motor and mask off any open ports in the case first. Frankly it seems like a lot of fuss when soldering is such a quick and easy job.
(That, incidentally, is my last word on the subject.)
DM

[John Thornton 1Participant @johnthornton1]

Posted by Malcolm Frary on 27/09/2013 21:17:06:

Any screw connector is liable to work loose if used where vibration is possible. Thinking back to old type telephone cabinets that were full of the things. Firmly planted to the ground, traffic vibration could do the job. Or undo it, as it were.

With choc blocks, there is always the uncertainty of actually getting a solid metal to metal connection, and when it is got, it is open to air. In the case of model boats, damp air. Damp air plus dissimilar metals usually equals trouble sooner or later.

 

I'm glad I read this–I was just about to use a choc block connector! Can you tell me what to use in its place to run several devices (ESC, BEC, R/C switches, smoke unit, etc.) from a single battery? Thanks.

Edited By John Thornton 1 on 30/09/2013 22:48:46

[Colin BishopModerator @colinbishop34627]

The points made about choc blocks are good ones but i have always used them without any problems. Mine are always easily accessible and can be checked for tightness at regular intervals.

And they are very convenient to use. The plug types are handy too.

Colin

[Dave MilbournParticipant @davemilbourn48782]

I'm glad I read this–I was just about to use a choc block connector! Can you tell me what to use in its place to run several devices (ESC, BEC, R/C switches, smoke unit, etc.) from a single battery? Thanks.

ACTion P92 or P102 distribution boards. They use rising clamp connectors which don't make single point contact with the cable or try to amputate it when tightened.

DM

[Paul TParticipant @pault84577]

From the comments made I can appreciate why there is a concern over choc block connectors but I really think that this worry is misplaced as during a lifetime in the commercial construction industry I have never encountered a problem with choc blocks being used in either mains electric or micro electronic components.

I should say that in all cases the correct size connector is used with the appropriate size of wire.

[Dave MilbournParticipant @davemilbourn48782]

(Following a request from Paul T on Bob Abell's thread on his version of Ellie, I have put this together for those who feel they might need more information. Frankly I think it's just Paul winding me up again, but there you go………)

This is not the easiest subject to explain and I would question whether most modellers really need to know at all! There are probably hundreds of different websites which all do it better than I can, but here goes anyway:

Capacitors have two internal plates which are separated by a non-conductive material called a dielectric. If you connect them up to a DC supply then these plates become quickly charged up (one positive and the other negative) to the same voltage as the supply BUT because the plates are insulated from each other they will not allow a direct current to flow between them. This is why you can fit one across a DC supply without it short-circuiting the whole issue.

A DC motor not only spins when you apply a voltage across the brushes but also acts as a voltage generator of what is know as back electro motive force ( or “Back EMF" ) when it is rotating. This e.m.f. alternates in polarity as the commutator of the motor rotates and the brushes act as on/off switches to the generated current. This will produce unwanted transient voltage spikes superimposed onto the speed controller/battery circuit and also quite possibly will generate electrical sparks at the brushes. These sparks are like the old-fashioned crystal radio sets i.e. they result in the transmission of a spurious high-frequency radio signal (RF).

Both the voltage spikes and the RF interference will adversely affect any connected electronic circuits. A capacitor will allow alternating current to flow between its plates because they alternately charge up and discharge with the changing polarity of the supply. This means that you can ‘dump’ an unwanted flow of alternating current to ground (usually the motor case) via the capacitors connected to the brushes and smooth out the unwanted ripples in the motor supply caused by the voltage spikes via the one across the two brushes.

The values aren’t critical so 0.1uF – 0.22uF is generally used for the latter while the ‘dumping’ suppressors between the brushes and the motor case can be as little as 0.01uF. Ceramic disc types are the best (and cheapest) as they can withstand the higher voltages, but you should avoid electrolytic types as they are polarity-sensitive and will go bang as soon as you reverse the direction of the motors. You wouldn’t believe how much insulating tissue wadding could fit inside such a tiny can………..

OK – it's now open-season for all tecchies to shoot me down in flames! Just remember that I was pushed……

Dave M

Edited By Dave Milbourn on 28/11/2013 17:38:24

[Malcolm FraryParticipant @malcolmfrary95515]

The only, very minor, missing bit is the advice to fit the capacitors as close to the motor as possible and to keep the leads short. The capacitor leads carry the interfering current, so the shorter the better, less chance to radiate. They are generally short legged devices, but I have seen heroic efforts at bad siting and leg-lengthening.

[Dave MilbournParticipant @davemilbourn48782]

Heck, Doc – there was loads more missing than that! But thanks for pointing out a practical thingy.
Dave M

[Malcolm FraryParticipant @malcolmfrary95515]

Interference and its avoidance can be a vast subject, but in the interest of avoiding the arcane maths that probably still lives under the dust on my old tech college books, boiling it down to a few lines will work for most of us very well.

Most modern motors have got to the stage where accuracy and materials used minimize their interference generating, but some older motors, however much is done to them and/or around them, will never play nicely with a radio.

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