Electrics

[Robert WaltersParticipant @robertwalters31200]

Hi you electrical geniuses out there, hope you can help me out.

Question 1= Is there a formula for working out the capacitors to solder onto motors to stop interferance.Do you need different size Capacitors for different size Motors

2 The model I am just starting to build has 4 Motors fitted, I wish to have them wired as pairs i e one stbd to one port, can any one advise on what parts I will need and a diagram (I am no electrician so if someone can, please make it simple)

[Robert WaltersParticipant @robertwalters31200]

[ArneSParticipant @arnes]

Mr Walters,

I’m sure some would say that capacitor size was critical but I have found that  0.01 to 0.1 microfarad seems to work for me.

As to wiring the motors, you need to specify if you want the pairs in series or parallel before a diagram can be supplied.

ArneS

[60wattParticipant @60watt]

I don’t claim to be a genius.The wind just blew me past motors on the way to electronic engineering so it is bread and butter stuff.

 

Robert you say you are coupling the feed from one starboard motor to one port motor.I can see the logic of doing that on a plane.

Perhaps you mean the inner and outer motors in pairs,one motor pair on either side?

 

 Decouplng motor generated r.f. interference.

 link 1 Typical low cost ceramic caps to suppress model motors

 

The microfarad values are not critiical but the capacitors should be the lowest k ceramic you can get.It is counter productive to fit higher numerical capacitor values if they are polyester as they don’t  decouple high frequency radio well due to their higher inductance. (see #4.0 in link2)

 

Lower frequency radio interference (0 to 30MHz) feeds back to the radio receiver through cables and so the capacitor across the motor terminals (RIGHT) should be ceramic  .01 to 0.1  microfarad to form the lowest impedance at lower radio frequencies. ( .01uF is a high capacitance value when you look at it at radio frequency)

That capacitor is the basic minimum.

Going further

You might find some motors have the two capacitors on the left already fitted inside the case.They should have a value of 0.01 to 0.01 microfarad on short,low inductance leads.

They filter out 30MHz to 1GHz which can be better decoupled by using the motor case as a screen.

 

A ground plane would be a  water (via rudder or stern tube) in the case of a model boat and a metal case in computers ,radios or power supplies.

Don’t fit the two left hand capacitors if you are not prepared to ground the motor case to water.In computers and radios  the earth strap to the ground plane  is low inductive braided wire but that is overkill for model boats.

 

If you need the logic behind the microfarad values and why the decoupling capacitors should be ceramic start googling the terms

“capacitor esr”,esl,

“decoupling capacitor”  or start surfing:-

link2 Capacitor charecteristics

link 3 Decoupling capacitor  (Wikipedia)

 

There are even further measures to completely eliminate motor interference but I’m not going there because nobody bothers with them.They blame their equipment.

[Robert WaltersParticipant @robertwalters31200]

Hi Arnes ans 60 WATT, thank you both for your prompt reply to my Questions. I have now fitted  capacitors to the motors taking your advice. as regards the wireing in pairs, my intension was as you said 60 watt. to wire say the left inner to the right outer and visa versa with the other two, this was so if I lose power on one pair I will still be sble to control the boat in a straight line and bring it home.(that is my theory)

Wether to wire them in series or parallel whichever way you think  will be more efficient.

As I said in my profile “I am a retired heavy plant fitter” I new how to sort Hydraulics out and swing a big hammer but electrics, no way.

Once again thanks for your information and the prompt reply. R Walters

[60wattParticipant @60watt]

Hi Robert.

A left pair and right pair is the norm and rudder control would adequately compensate.

Parallel connection on motors.I cant fathom that series motor connection business at all.

If efficiency is an issue then max eff. is achieved by lightly loading dc motors so that a prop slows the motor down to 75% of its no load figure..Maximum power requires a slightly larger prop but there is a  common tendency to overload motors.

If you have motors that turn like a turbine and big props you may even need a gearbox.

[Dave MilbournParticipant @davemilbourn48782]

Robert

There are a couple of wiring diagrams on the ACTion website which show installations of four motors (Large battleship and USS Enterprise). If you could let me know more about the sort of motors i.e. size, type, voltage and the type of model then I might come up with an alternative for you.

It’s not rocket-science or black magic!

Dave M

[Robert WaltersParticipant @robertwalters31200]

Hi 60 watt.

The parallel or series connection was suggested by Arnes. Thanks for the rest of the information, takes some sinking in but I will get there in the end. Bob

[Robert WaltersParticipant @robertwalters31200]

Hi Dave

Thanks for your reply,the model I am constructing is a scratch built “Fairmile D long range Rescue craft” I/32 scale Overall length 1200mm, Marine Modelling plan No2148

Motors are EXPO Std 380s 4 in Number paired off (it states on the plan) using 2 BOBs 8 amp boards (this to me is a mystery).

I went looking for the ACTion website (actionkit.co.uk) but couldnt get the actual site all I got was a list of different wweb sites to click onto. so which site are the 4 motor installation diagrams?

[Colin BishopModerator @colinbishop34627]

This is the ACTion site: http://www.action-electronics.co.uk/

 

Click on “Diagrams and Articles” to see the wiring diagrams.

 

Colin

[ashley needhamParticipant @ashleyneedham69188]

Maplin`s do electric motor capacitors, you get three in a pack, two for terminal to case,m and one terminal-terminal, and i have no idea what size they are, but it doesn’t really matter as you simply buy the pack, fit and forget. Ashley

[60wattParticipant @60watt]

Hi Robert

   The mention of  “bob’s bored” landed with a thump! Forget what I said about parallel connection

   Forget the bobs boards if you have not already bought them.They need careful selection depending upon the amp draw of the motor used if any form of speed control is to be achieved.The current drain of the motor depends on the propeller.

 If you watch boats on a pond you could spot which ones employ bobs boards.

 

[ashley needhamParticipant @ashleyneedham69188]

60…the main problem with Bobs boards is that they are always drawing max curent even when the motor is on a small throttle…is that correct?? or is it urban myth…   Ashley

[Paul TParticipant @pault84577]

Dear all

 

Although they do have drawbacks Bobs boards are a very cheap way of putting speed control into smaller models and if it were not for them my early models (many years ago) would not have been so much fun.

 

They do draw a huge ammount of power, get very hot and wear out quite fast but for a young lad building his first models they were super.

 

Paul

[Bob Abell 2Participant @bobabell2]

Can I butt in here………………….Just joined thr thread late on, so I haven`t read the early stuff…………………….But I use Bob`s Boards on most of my models…………….they come as a very nice set complete set,  from MFA with all leads plugs, motor couplings fuses and sockets and best of all……the capaciters are already soldered to the motor body

 

Just passing……………………Bob

[60wattParticipant @60watt]

“….is that correct?”

Wait a minute,Ashley…….two sixes = No. But I do know where you went wrong with your sketch.

I found at a venue where they “build them big” you could get no better throttle response than you could by occasionally tapping on a microswitch.

I have the materials at hand to home made rheostat I  would be quite happy to sail all models but for the fact Idon’t want the extra breakdowns.

 

Hey Bob.

I was logged,typed the above message,hit the add posting button and got logged out because you pipped me to it.

Colin,call the techies at once.

[Bob Abell 2Participant @bobabell2]

Here`s my Bob`s Boards in Great eastern……..just for interest

 

Hey 60 Watt!……………How do you know it was me that knocked your “log in” out?

 

Perhaps, this could be my problem too?

 

Bob

[60wattParticipant @60watt]

Bob,I thought the same.

It would be simple enough to check whether that or a time out occurred.

 

Steering closer to Robert’s topic,perhaps I should make clear that I noticed that the inertia of the very big models meant they would respond no worse to pulsing the motors on-off than with any form of speed control. 

——

I’ve just remembered what happens when you loose radio contact when sailing with a rheostat control……Crrrrunch!

 

[Glynn GuestParticipant @glynnguest59245]

I hesitate to be critical on this forum but I cannot see any “Bob’s Boards” in Mr Abells picture posted today 0914.  I do see some variable resistance type of controllers that were once popular in the RC car field.

GlynnGuest

[Paul TParticipant @pault84577]

Bob

 

Glynn is right these are form RC cars

 

Come on you old fool and get your facts right

 

Paul

[Robert WaltersParticipant @robertwalters31200]

Hi All, “Jeez what have I started” I only wanted to know about capacitors and how to wire the four motors in pairs the most efficient way. I didnt want to start WW 111. In the past I have built models with only one motor, which are quiet simple to wire up, when I ask for informarion about four motors it ends up with people calling each other “old fool” and knocking each other off the air, and my problem still isnt solved. R Walters

[Robert WaltersParticipant @robertwalters31200]

Thanks Dave Milbourn for suggesting the Action web site and thanks Colin Bishop for passing on the web site address. Have now printed out a wireing  diagram for the 4 motors. Once again thank you all for your time and information, no doubt in the future I will be asking for some more advice, I hope you all will respond as quickly the next time. R Walters 

[Colin BishopModerator @colinbishop34627]

Glad to have been of help Robert. If you need any more advice just ask.

 

Colin

[Bob Abell 2Participant @bobabell2]

Just spotted the latest postings, referring to my erroneous thinking about Bob`s Boards etc……………..having been out for the day

 

So what`s a Bob`s Board then?

 

Bob

[Paul TParticipant @pault84577]

Bob

 

This is a Bobs board

Sorry its not a very good image.

 

A Bobs board is very like the speed controller that you use except that it is flat rather than round.

You can see on the photo where the arms wear out the circuit board as they turn.

 

Look at this link for more info http://www.modelboatmayhem.co.uk/Common/Electrics/Speed%20controlers.htm

 

Paul

[Author]

Posts