Problems with electric drive

[MzeeParticipant @mzee]

I have an electric drive ‘misfire’!

[MzeeParticipant @mzee]

My equipment is:
Viper Marine 25 driving a MFA (Como Drills) 919D motor from a 12 volt 7.5AH rechargable sealed lead acid battery. Radio gear is Hitec Ranger II on 26.995 MHz and linear distance from controller to receiver is about 180mm.  Motor and ESC are both brand new: never used before.

My problem is:
At full ahead the motor momentarily and intermittently cuts out for brief moments but at half ahead and full astern it does not do this.

Attempted cures:
The 919D motor comes with a capacitor (of no indicated capacitance) between + and – leads.  I tried adding a 100 uf capacitor to this – in parallel – with no success.  I then tried a 10 uf capacitor between each lead and the motor casing, with and without the 100 uf capacitor between leads.  None of these combinations worked.  I have also tried shielding the receiver with aluminium foil.

Any suggestions on a cure?  Would braid screening/shielding around the servo leads help?  The antenna goes directly from receiver up through the aerial tube. Might there be an internal problem with the Marine 25 controller (This is brand new and not previously used on any other model)? 

I have Viper controllers in three other boats, one of which is a large tugboat with twin motor setup and two controllers which are only about 80-100mm from the radio receiver.  This is the first time I am using the 919D motor and initially suspecting there might be a problem with the motor changed my setup with an identical unit – both had this cutout problem on full ahead setting.

 

Mtroniks made this suggestion which doesn’t sound right!  “

It sounds very much like the motor is pulling too much current for your battery at full forwards speed.>>

The way to cure this is to fit a large capacitor across the battery input wires to the speed controller.>>

> >

You will need to purchase a 10,000uF 16V capacitor and solder it across the battery wires on the speed controller (as close the controller as you can) you will need to remove some of the wire insulation to allow soldering to the wires.”>>

 

PLEASE can somebody help?

Thanks, Rob

[60wattParticipant @60watt]

Rob,the Mtroniks remedial suggestion is effective where you have long supply leads from the battery and a voltage failsafe

The 10,000 uF capacitor would stop a problem due to supply voltage dropping below a minimum threshold.

Edited By 60watt on 15/02/2010 14:10:49

[MzeeParticipant @mzee]

Thanks 60W. 

 

Lead length battery to ESC is 20cm and motor to ESC is 40cm – which is about half what I have in my large tugboat.  I don’t know what max amperage the 919D motor pulls but I’d have thought that the voltage drop on a freshly-charged 7.5AH battery would be negligible (The ‘misfire’ problem happens immediately when I ask for full ahead – not after I’ve ‘played’ for an hour or two!).  In addition the ESC is powered from the receiver battery (red wire cut as per instructions!) which comes from also freshly-charged Uniross 2000mAH pencells.

 

Unfortunately I live in a place where I can’t nip around the corner to buy electronic stuff so I shall have to try the Mtroniks suggestion when next I go to the City like in about two weeks

 

Thanks again,

Rob

[60wattParticipant @60watt]

Rest assured you don’t have anything faulty and you are not the first person on this forum to have problem with a geared 540 on 12 volt.

 

The cable length does not seem so excessive such that a voltage failsafe would operate.

The advice given to you is only as good as the information you give to Mtroniks and they would know best how the controllers behave in different installations.If you left any information out,keep up the dialogue.

[glennParticipant @glenn]

Hi Rob, is there anyway you could swap esc for 1 in your other boats to see if its the esc causing the problem. its unlikely the motor is pulling to many amps to cause an overload. Its not unheard of to get a faulty viper esc.

 

cheers Glenn 

[MzeeParticipant @mzee]

Yes Glenn.  I am about to do just that but other commitments prevent me from doing this until the week-end.  I’ll post the results.  Cheers, Rob

[ashley needhamParticipant @ashleyneedham69188]

I have this on a few of my boats, notably the Sunderland , and its always due to receiver reception or lack of good reception,always cured after a bit of fiddling with the receiver lead/ariel.

 

I think that the Viper controllers are a bit sensitive to this, my Oberon submarine was dreadful until changed the ESC, then, no trouble.

 

Ashley

[MzeeParticipant @mzee]

Many thanks Ashley – I obviously need to spend time ‘fiddling’.  I cannot find a 10000uF capacitor and wonder if perhaps both Mtroniks and ’60 watt’ mean 10000pF (as per Maplin’s cat # SC85G)?  Never had problems with these old ‘klunkers’ which have been powering some of my models for 30 years!!!

Rob

[MzeeParticipant @mzee]

Oops!

[60wattParticipant @60watt]

Rob,what do you reckon on the chances of two electronic engineers confusing the two? 10,000pF on the left and 10,000uF,16volt electrolytic on the right.

 

If you have a broken stereo,telly,radio or even a plug in psu,you will find a large value electrolytic capacitor,but honestly,don’t even bother.

The suggestion by Mtroniks was to put it across the esc power feed but unless there is a voltage failsafe configured to protect a Lipo then it won’t do any good.

 

[MzeeParticipant @mzee]

’60 Watt’,  I never throw away anything that might even remotely be useful one day!  In my ‘junk box’ I have stuff that went in there in Kenya up until 1962 and then more went in in England for the next two years and since then even more useful stuff (junk to my wife) has accumulated.  Anything that might one day be useful is stripped and only the bones chucked away (sometimes!).  So, yes I took a look at some of the electrolytic condensers recovered from old PC monitors, radios and a few Tape players/recorders, and they are almost the size of the 919D motor.  Hence my query whether the value might not have been pFs and not uFs!  It’s so easy to read what you expect to see rather than what is actually written, isn’t it?

 

So, back to my old Maplin catalogue ……  Thanks and have a great week-end.

Rob

[60wattParticipant @60watt]

The value (10,000 uF ) suggested by Mtronics was not a mistake and has the same remedial effect as in a particular auto application.See Maplin A07GU

The suggestion would have been made on incomplete or erroneous information.

 

Your boat,on the other hand, could do with ferrite suppression(see picture) on your motor cables and connecting the motor case to the battery -ve.For safety’s sake I would use a 22 ohm resistor to make the link.

 

[MzeeParticipant @mzee]

Thank you, Gentlemen all, and apologies for the long delay in responding to your helpful answers.  I have been somewhat incapacitated for a while (pun intentional ).

 

I eventually fixed the problem by soldering 0.1 mFd capacitors between leads and from each lead to motor casing.  

 

Regards,

Rob

[ashley needhamParticipant @ashleyneedham69188]

Ah Ha! The easy things… i fitted the radio gear in my battleship on Saturday, and the motors/rudder worked ok.. but the rudder was juddering something chronic. i fiddled with the positions of the stuff to no avail…and looked at the motors.

 

They were low powered 540`s from MFA…pre suppressed with a cap across the terminals, and so i added the rest.. caps from terminal to case, and hey presto..no juddering.

 

I hesitate to say it..but possibly this really is all you need in most cases?

 

Ashley

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