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Author Topic: supression?  (Read 2594 times)

colin-stevens

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supression?
« on: May 25, 2009, 07:47:07 PM »

do brushless motors/esc's need suppresion? ask because i am getting some weird reactions on 2 esc on a Y-lead off of 1 channel.
colin
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stallspeed

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Re: supression?
« Reply #1 on: May 25, 2009, 07:54:14 PM »

Not on the motor but if you share the battery between two escs or use a ubec you should coil the esc servo leads through a ferrite ring.That stops a circulating current.
Grounding the motor cases also helps.
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colin-stevens

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Re: supression?
« Reply #2 on: May 25, 2009, 08:54:28 PM »

take it you mean the esc leads. if so, where on earth does one get a ferrite ring. does it need to be colied at the esc's or at the single lead of the Y-lead?
at the moment i am using a dedicated battery for the receiver as using one of the esc's as a power scource created other problems.
colin
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stallspeed

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Re: supression?
« Reply #3 on: May 25, 2009, 09:12:14 PM »

The brushless aircraft esc suppliers sometimes supply the servo cable looped through a ring.

I actually meant a separate switching bec called a ubec which is piggybacked to the esc supply to power the receiver.It is used in planes if the escs dont have a 3 or 5 amp bec and digital servos.
If you had a single propulsion battery and two speed controllers (or a ubec) you create two parallel paths between the propulsion battery and receiver negative.A ferrite ring on the servo cable blocks interference caused by motor current looping through the parallel connection.
Before you think about suppressing a brushless installation though,it would be better to find out where the problem came from.What is your radio?

p.s. google your esc name with the word interference.
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Subculture

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Re: supression?
« Reply #4 on: May 26, 2009, 10:09:42 AM »

Ferrite rings can be found on lots of appliances. I get mine by stripping down old bits of kit and salvaging them. Redundant (i.e. blown up) computer PSU's usually give up a few, they look like oversized polo mints with lots of wire wound around them. Computer fans often have the power leads wound round a ferrite ring.

I snip them off the board with a pair of wire cutters, and cut off the wire.

You can also purchase them new from Maplin in a variety of diameters.

Andy

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Re: supression?
« Reply #5 on: May 26, 2009, 10:11:23 AM »

BTW, have you disconnected the red wire from one of the servo plugs on the ESC's?

If not, and the controllers use BEC, then you will have two BEC's feeding into the power bus. That will put you through all kinds of hell.

andrewh

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Re: supression?
« Reply #6 on: May 26, 2009, 12:12:28 PM »

colin,

basically no, they don't in the same way as brushed motors.

Can I suggest creeping up on this problem - one step at a time.  Do you have a servo tester?
They are the most magic thing since the predecessor to sliced bread - and save setting up a Tx Rx to test stuff.

However I suggest you try (with either a servo tester or Rx) each of the ESC/Motors seperately using the bec in the ESc if that is what you are going to use. (if you use a seperate RX battery you MUST disconnect the red lead in the ESC or you will get indeterminate fighting going on)

Try both on their own, change over motors, try again.
Still OK?
Try both on the Y-lead (BOTH red leads removed if you are using a Rx battery)
(ferrite rings may be useful, but I don't think you have the kind of problem that they would help with)

Did ANY of these tests run smoothly - without the "weird reactions" you mentioned
andrew
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colin-stevens

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Re: supression?
« Reply #7 on: May 26, 2009, 10:53:52 PM »

ok, more info. using a Futaba 40Mgh set. both RED leads removed from ESC(speed controllers)
only noticable on the water, when coming out of a turn, or applying full power, she "twitches", as if a motor has cut out, or there was a lot of torque on one side. occasionly i would lose steering, only to get it back.
(also when i got her back i found the servo gears had stripped. this has never, ever happened to me before.)

one thing that crossed my mind was maybe the receiver battery was'nt up to the job.
another is that if the rudder servo was on its way out it may have "interferred" with the ESC's

query, does it matter how many turns wound round ferritr ring? and do you do it to both ESC(speed controllers)

colin

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malcolmfrary

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Re: supression?
« Reply #8 on: May 30, 2009, 12:04:37 PM »

For the purpose of keeping radar out of telephones, we used a pair of 1.25" ferrite toroids taped together.  The recipe was " tightly wrap 13 turns of the line cord around the ring in a single layer, leaving a 1/2" gap".  This was to put as much wire as possible in there, on the grounds of "the more the merrier".  The important words were - single layer and tight.  The same is probably true for this application, but every turn is a bit more length in the motor lead.  If the original leads are being used, shouldn't be a problem, but if the leads need to be lengthened, increasing resistance might lead to other problems.
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colin-stevens

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Re: supression?
« Reply #9 on: June 02, 2009, 06:50:43 PM »

sory losing the plot here. thought the ESC-receiver leads were wrapped around the widgets?
too much for my single brain cell to handle
colin
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stallspeed

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Re: supression?
« Reply #10 on: June 02, 2009, 09:28:13 PM »

I mean't thread the servo cable through a widget because although it is not the cure for likeliest of problems,it is as easy as unplugging a servo.(if you have a ferrite polo mint).
The problem that cures is noise on the signal to the escs where you hook both escs to one supply.I thought you implied the problem was confined to the escs when I suggested that.Forget it as it is not a cure for radio problems.

I suggest you try Andrewh's method.
With no servo tester,you can observe a servo in a spare channel to pick up signs of radio interference.You can eliminate the rudder as a source by unplugging that servo.Hold on to the boat and give it a burst of throttle.



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malcolmfrary

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Re: supression?
« Reply #11 on: June 02, 2009, 09:33:22 PM »

Sorry, Colin, silver moment on my part.   :embarrassed:
The toroids can be used anywhere, power or low signal.  Use extension leads between the Y junction and ESC, and put as many turns as you can, in a single layer, wrapped tightly and laid flat, leaving a 1/2" gap of ferrite showing.  This to ensure that the interfering signal doesn't hop across.
Just how effective they may be is an open question.
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colin-stevens

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Re: supression?
« Reply #12 on: June 04, 2009, 03:20:45 PM »

cheers guys. remains to be seen wether this cure the problem, but worth a try.
colin
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