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[Tug-Kenny RIP]

Another techie problem has come my way    (why me)

I decided to raise the  motor voltage to 12 volts instead of 6 volts.  I have changed the servo 4.8 volt battery for the old  6 volt battery and invested in a 12volt  7Ahr. for the motors   (I 'm not sure if it will float now !!)

I wired it up on separate supply lines and now, when the motors are accelerated I find the servos start judderring all by themselves until max speed is reached, then it all cuts out with the ESC's flashing their lights.

My question is this.  What voltage is supposed to be on the servos, as this also runs to the ESC's.  I seem to be getting half a volt coming back up the 6 volt line from the 12 volt battery.  :(

Hope you can help


Cheer...Ken

[Shipmate60]

What ESC's are you using and have you disabled the BEC if the ESC's have one?

Bob

[FullLeatherJacket]

Hi Ken

Most radio systems run from 4 cells. If they are rechargeable then that is nominally 4.8 volts, although a fully-charged pack can register over 5.5 volts. With alkaline cells it's 6 volts, but that drops quite quickly under load.

I'm not sure what you've done to cause such a commotion, but if I were you I'd completely divorce the power supply to the motors and ESC's from that to the receiver and servos. If the model you are talking about is Aziz then you have a shed-load of room for a decent 4-cell NiCad or NiMh pack dedicated to the receiver and servos. More folk than I could count have come to grief by trying to power the motors and radio from the same supply. I've been lectured until my nose bled about earth-loops and other things I couldn't even imagine, so I try to adopt KISS every time (Keep It Simple, Stupid). Have a shufti at the Mayhem site here:
 
http://www.modelboatmayhem.co.uk/Common/Electrics/Images/setupsA4JPG.jpg

Keep the power cables for the motors etc well away from the receiver and antenna wires, and make sure you have soldered suppressor capacitors across the motor terminals (details elsewhere on this forum, or PM me)............and avoid BEC.

Works for me, but suit yourself anyway.

[Mankster]

Most modern servos will run happily off 6 volts though there lifespan may be reuced slightly.  RX's should be fine on 6v aswell. Make sure you have disabled the BEC on the ESC (disconnect red wire to the Rx), and try fitting suppressors to the motor.

[HS93 (RIP)]

I ran model cars for a long long time and we would try to use 6v to keep the servos as quick as possible in cars they did not last very long due to impact I still run all my stuff of 6v in boats i don't like becks in boats so run on 5 nicads I only do this so if the drive battery is going flat or you ask to much of it you don't get glitches I did look on the futaba web site and found this though

http://www.futaba-rc.com/faq/product-faq.html#q109

My expensive, ball bearing servos 'buzz', 'humm' or 'chatter', especially when I first turn on the receiver.

MY standard servos never did this. What's wrong? What do I need to do?
We often receive calls from customers who will mention that they notice "servo chatter" in their ball bearinged servos.

Always check your linkages and set ups for binding, servos fighting each other on the same working surface, and bad extensions to be sure that there's no problems in your physical system.

Assuming there is no binding or other issues, buzzing is a common and harmless occurrence, and indicates that your servo is "checking" itself for true center. There will many times be an audible "buzz" from their servos, even when there is no noticeable movement. And this is also harmless, as when the plane is airborne, the wind over the control surfaces, and thus load on the servo itself, will correct this small amount of vibration and noise.

Many times if a modeler is using a 6 Volt receiver battery, or a completely fully charged battery, they will notice buzzing, but, when the voltage drops slightly with some amount of load, the movement and noise subside. This is commonly known as 'a hot charge' and again is perfectly normal and will subside under loads and particularly in flight



there was allso this that may be usefull to people with fast boats




Why are S3003/S3004 servos not to be used in helis?

Both the S3003 and S3004 use a direct drive potentiometer. What that means is the output gear is connected directly to the potentiometer. Since the output gear is connected directly to the pot it is very possible that vibration will damage the pot. This is why we do not recommend these servos to be used in helis. Helis generate a very high frequency vibration due to the high rpm of the engine and the close proximity of the engine to the servos.



Peter

[Tug-Kenny RIP]

 Wow. Thank you everyone.

Had a sleepless night, wondering what I had done wrong.  I shall revert back to 4.8 v on a separate line.

My only concern was the smallness of the battery, as it goes to the RX, four servos, three ESC's.

Back to the cold shed....


Cheers...Ken

[FullLeatherJacket]

Ken
Don't worry, mate. You can get AA-sized cells over 2 Ah these days (NiMh); that should run your radio for hours. Try Modelpower's website; John could do you a properly made-up pack with plug etc for £not-a-lot. I've used his stuff before with no complaints > suit yourself.
FLJ

[HS93 (RIP)]

There is no reason why you cannot use SUB c or even D size for receiver packs in  SUB c you can go up to 4.4ma and soon even higher
the fly boys use big packs because they runlots of servos and giro's etc  Peter

[wombat]

Hi Ken,

If you are using the M-tronics viper ESCs, then remove the red lead from the servo sockets, otherwise you will be backfeeding the 6V battery through the BEC driven from the 12V (not sure how the BEC is implemented in the Vipers)

I find a little bit of chatter on my rudder servo, but nothing to worry about. Other than that everything runs hunky dory - can you do a sketch of the layout you have, and maybe a couple of photos - you may have an odd current circulation path in there somewheres (Bane of my life at work). It is amazing just how complicated very simple circuits can get  :(

TtW

[Tug-Kenny RIP]

Well everyone.  I spent 8 hours today on this problem.

The latest situation is as follows.  The servos are wired to a 4 cell  Nmh battery and work flawlessly.

The Mtronic ESC's are wired direct to the 12volt battery through 5 amp fuses   (all the 10amp ones gone till the shops open !!).

The motors are wired direct to the ESC's.

It all works OK until the motor revs exceed half speed. The problem is, when it goes faster. They cut out for a split second and then come on again.   ( sounds a bit like a war time motor cycle in a country lane at night )  (don't ask !!)

If I go to top speed, the motor stops and All the ESC's start flashing their lights and the servos chatter. ( This is the bit I'm not keen on !!)   Looks great on the oscilloscope.

I have downloaded the Mtronics blurb and saw an item on suppression so I have fitted 1000uF capacitors right at the ESC's.  This has increased my top speed to 3/4 until it breaks up, so I am alright until I need top speed.  ( any river police about !!)

I reverted to the 6volt battery and it worked fine.  This tells me the ESC's are breaking down under the higher voltage.   They could well be damaged by now, and the makers will not have them back, as the wires have been cut about a bit.  ( the bow thruster motor goes very fast without breaking up, probably because it never was in the original frame of disasters) 

I would try it's ESC in place of one of the others, but it's all hard wired in-situ now and I don't want to go through it again.

There were some pics included with this but the server crashed,  (story of my life !!),   so I'm trying again without them. See later letter if I can get them up and running.

Thanks for listening


Cheer...Ken

[Tug-Kenny RIP]

here we go with the PICS

Cheers...Ken

[Faraday's Cage]

Hi Ken,

Just to clarify a few points.

Youre using separate batteries for both receiver supply and motor supply ?

Have you disconnected red wires from the speed controller plugs that plug into the receiver socket ? If not then do so as all this wire does is supply the receiver with 5 volts from the BEC circuit in the speed controller which will conflict with your existing receiver supply battery.  Its possible to take the pin out of the plug with red wire still still attached if care is taken. This way you can reinsert the pin if required at a later date.

I may be teaching you to suck eggs as I dont know your capability.
Good luck, Terry.

[Tug-Kenny RIP]

Hi Terry.

Yes, I have removed the middle wires from the ESC's. This is because I have two batterries

Mind you, the previous history include wiring up this BEC wire when I had it running on the 6 volt battery only.    I discontinued this way when I realised the 6 volts was going everywhere.

Thanks for your input.

I shall start sealing the deck soon, so I shall be working through the holes from now on !!!   rather like wallpapering the Hall through the letter box.

I have also noticed the prop shafts have bowed in a bit  (under the weight...perhaps) and now the props foul the Kort tubes.   and it's all glued up and technically finished...ugh !!!.    I thought brain surgery was hard enough !!!     

This is a fun hobby


Cheers...Ken




Cheers...Ken

[Scottie]

Ken, not certain if this is revelvant here but computerised radios can 'overdrive' Viper' esc's resulting in what you are experiencing. Also, I had a pair that did strange things when the red wire was not connected to the receiver.

Scottie

[tigertiger]

There is reason why you cannot use SUB c or even D size for receiver packs in  SUB c you can go up to 4.4ma and soon even higher
the fly boys use big packs because they runlots of servos and giro's etc  Peter

Q HS93
Should this read 'There is no reason...'?

[HS93 (RIP)]

YES

[Telstar]

Hi.  In Tug Kenny's post
I have fitted 1000uF capacitors right at the ESC's.  This has increased my top speed to 3/4 until it breaks up, so I am alright until I need top speed.  ( any river police about !!)
I started to wonder what size wire you are using from your main battery to your motor circuits. If I have got it right on how ESC's work, they pulse the power to the motors so the current showing on an ammeter is not the maximum current in the wire. In this case is the current being take by motors causing too much volt drop in the wire. A 1000uF capacitor is big for just suppression, and will act like a mini battery close to the ESC's helping smooth the supply, and remove some of the pulses from the battery side. Maybe the wiring from the battery is a bit on the small side, I would guess it would need to be capable of carrying twice the required average current (ie. for two motors of say 12A the wire would be able to carry 48A ). As a senior citizen I remember volt drop trouble with VW beetles there 6V battery (in the back) and 48watt headlights were a bit dim, but adding a pair of spotlights to the same wiring from back to front of the car dropped more volts and made the overall lighting worse not better. 
But I digress, perhapsthe wire is a bit on the small size (in cross section) and the wire runs a bit long. Don't know ,just a thought.
cheers Tom

[Tug-Kenny RIP]

Thank you all for your input. I must say I'm overwhelmed by your kindness and consideration.

It would seem the reasons for my troubles are approaching it like an electrician. A little knowledge is a dangerous thing !!

I shall check the following tommorrow and report back.

1.  The wire runs are too long
2.  The wire might be OK for a TV, but not boat building.
3.  The ESC's are breaking up with the current overload  ( I have purchased a 20 amp version today)
4.  The 2.3:1 geared motors are wrong for 12 volts  ( excessive current at speed)  should be 6:1 gears
5.  My glue has dried up, as the top fell off days ago !!!

I have to get it right, as my "Mrs" thinks I'm not all there.   :)


Cheers...Ken

[wombat]

Hi Ken,

Scanning the photographs, I wonder if some of the problem is the length of the cables - they are running the length of the boat. I'm not sure it is a compatibility problem with the receiver/radio set - I am using the same reciever.

The cables to the main motors could be a little thin. The other possibility that occurs to me is that if you are running the power leads in the same trunk as the servo leads you could be getting spikes from the power lines coupling onto the servo lead giving a spurious signal. In moving to 12V this problem will be made worse.

The 1000uF will help - though it will not really get out the high frequencies. You could drop a 10uF tantalum and a 0.1uF ceramic if you have them handy

Try moving the servo leads to the other side of the boat.

TtW

[Tug-Kenny RIP]

Hi Wombat

Another nine hours today.......feels just like a job.

You were correct. I pulled it all to bits and laid out the motor with the ESC on the bench. I laid the TX with it's battery also on the bench and switched on.  WORKED A TREAT.    :)   :)   :)

I had wired the servo wires all together in the tube along the length of the boat ( 3ft) and they were the cause of my glitches.  Thanks for pointing out this mistake.

The rest of the day was spent re-locating the bits and re-wiring the whole thing at the stern. Some slight glitches were noticed but as another member pointed out, we are dealing with computers and high speed pulses. I didn't mention that the TX is the Futaba 'Sky sport 6' and that it was located on the bench by the side of the hull when testing.  ooh err.   ???

Thanks for listening. Hope to move on to the deck soon


Cheers...Ken

[wombat]

Hi Ken,

Nine hours.....is that all, took you no time at all  Been there, done that, bought the tee-shirt and drunk the fizzy drink.

Not so bad when its a model boat - when it is a 300kV power supply the size of a van life gets interesting when the controls go haywire. My three rules for going into an HV area:

1/. You can't tell if it safe even if it is switched off - always go into the area second.

2/. Lightning takes the shortest path - always make sure that the person who goes in before you is taller than you

3/. Always carry spare underpants.

Tim the Wombat