Servo Glitch

Hey Troy,

Last comp, i spoke breifly to you about the glitches i was having with my whinch etc and i sorted this out but it seems when i turn my steering back and forth quickly it then takes on a mind of its own and rattles left and right and the whinch cranks out rope too. This lasts a few seconds.

Now i recall we spoke about this and you said something about an external BEC???? Mate this information went so far over my head it had ice on it.

So can you tell me how to stop this glitch and can you give me a schematic type set up of the wiring and how it should be done so that i can eliminate this piss me off situation. Also what type of equipment i'll nee dto buy, brands etc.

I run a savox digital servo

Thanking you sir

Jase

It may be taking to much power from your steer servo (the winch) but it sounds like you need a new steer servo to me.......'then maybe a bec aswell if the glitching persists.

Nah its just a BEC issue Scotty.....Jase, nathan and i were working on it at the last comp.

First off. What is a BEC?
A Bec is a Battery Elimination Circuit. BECs were designed to eliminate the need for a 2nd smaller 6v battery pack to power the RX & Servos.
What does it do?
A BEC is essentially a voltage regulator to step the main battery pack voltage down to a safe level for servos and the like (generally 6v or less).
99% of all modern ESC's have an internal BEC that steps down this voltage and powers the Rx (and therefore the servo's) through the small wires that go from the ESC to the Rx.

Now this internal ESC is restricted to how many amps and volts it can put out due to space and temperature restrictions of it being inside the ESC (Usually around 5v and 3amps or less)

An external BEC is able to get around this as all it does is regulate voltage, it is its own component and therefore is able to handle the big amp draw that comes with hi-torque servos without the space and temp restrictions of being placed inside another component. (eg. a Caslte BEC output is adjustable all the way to 9v and can handle 10amp draw)



So if we relate this back to the issue with you rig Jase.

The internal BEC of the FX-R is only 2-3amps constant (less if you are running 3s lipo). The Savox servo can draw up to 5-6amps at stall (full lock, steering quickly or trying to steer out of a bind). So what happens is it 'browns out' and shutting down the internal BEC of the FX-R, causing the Rx to lose power (remember the ESC's internal BEC powers the Rx) so nothing is getting signal and the steering and winch go ape-shite.

What an external BEC does is bypasses the ESC's internal BEC totally, directly powering the receiver and anything that takes power from the Rx (in this case steering servo and winch). Due to this and the fact the an external BEC is able to handle more amps it should stop the 'glitch' that you are experiencing.


The best BEC to get is a Castle Creations 10amp BEC. Like this (click)
They are $20-30 depending on where you go. But they only come preset to 5.1v. You will need to use Castle Link and the dongle programmer to change than up to minimum of 6v.

You might be able to get away with a cheap hobbywing/turning 6v/3-5a BEC like this (clicky).
I use one of these cheap BEC's in my honcho with a Hitec 7955tg servo and it works fine, and also run one in with mog without a hitch as well.


This is the wiring diagram off Castle's website:
But its the same for wiring any BECs through the receiver. You will need a spare slot in your Rx, the BEC usually plugs into the Batt/Bind port.


Hope that answers you questions mate...If anything is unclear let me know.

you are the guru of all things rc as i said jase wide load is the man to ask any questions and want a honest and clear answer

Troy

does that mean he will need one or two BEC's ?

Aperture wrote:Troy

does that mean he will need one or two BEC's ?

One Castle one would be fine. But you might need 2 cheapies but only testing would really show if its needed.

They are $20-30 depending on where you go. But they only come preset to 5.1v. You will need to use Castle Link and the dongle programmer to change than up to minimum of 6v.

If you don't want to buy your own Castle Link and live reasonably close to the Cornubia quarry track I have one that I use for tuning my Savage.

ntoff wrote:

They are $20-30 depending on where you go. But they only come preset to 5.1v. You will need to use Castle Link and the dongle programmer to change than up to minimum of 6v.

If you don't want to buy your own Castle Link and live reasonably close to the Cornubia quarry track I have one that I use for tuning my Savage.

I have a castle link for my 2WD Fastie. Thank you, and unfortunately Toowoomba is a tad far. hehehehe.

G'day Troy,

In relation to this glitch, i have been a tad bit slack, and not got around to doing this yet..... however it was only doing the glitch for a micorsecond and so i was putting up with it.

I went to have a drive today and well in true fashion to my laziness, the steering and winch went absolutely spastic, for like 10 seconds with the winch spewing out line, and the sterring looking like it had taken a hit of speed and was flipping out. Now with Q-Rock less than a week away, this major glitch is not going to be conducive to my driving.

So i know i'n throwing a spanner in the works, but is there a quick fix problem to bypass this without a BEC, i.e. you said something about putting a 6V power pack in is that like a 4 AA battery tube i have lying around?

I am goig to buy a BEC but won't have it by this weekend. Can you assist, and can you assist with setting it up.


Now by all means begin shaking your head at me, and start calling me names as I deserve it. If need be I am able to bypass to your pad early Sunday in
Redbank?? On my way to Q-Rock..

Help me Obi-One-Wideloady, you're my only help

Dont worry mate wont chew you head off....its an honest question. I sort of half covered it in the big blurb i put up about BECs previously but here's the stuff you want to know.

Yes you can use a external battery pack to power you Rx, Servo & winch.

So if you use the 4xAA tube you have and plug that into a spare port on you receiver it will work just like an external bec.

Just make sure you bypass the internal bec on the esc by removing the middle wire (usually red ) from the esc's Rx plug. All i do is carefully lift the little plastic tab, pull the wire out, then fold it back and tape it to the other wires to stop any shorts.


*Important Note* - Because you are going to be running straight power into the Rx that you will need to unplug the Rx battery pack to shut the Rx off. Also make sure that you turn you radio on first and off last now. If you forgot to do this your winch and servo will go nuts cause there will be no radio signal.


Let us know how you mate.

OK Here are some photos for you to look at, I'm trying to get my head around it for configuration, and putting together.

the first one is my battery pack.

[img][/img]

The second one is my radio transmitter??? The empty plug is where i unplugged my winch to avoid the wind on effect, so it is taken, the THR (Throttle), is attached to photo 3?? which is the ESC? STR (steering?) is my Servo. So this trnasmitter is where I'm getting my glitch?

[img][/img]


Photo 3
[img][/img]

OK so how do i put my battery pack in i.e. where do i plug it in, in the scheme of things?

And once i plug it in, the middle red wire on the STR needs to be removed Is that correct?

Yup that pack will be fine.

Plug the pack into BIND, winch into AUX, servo into STR and esc into THR

You need to remove the red wire from the esc (THR) plug.

That should be it.

EDIT: Dont forget to actually switch the truck off totally now you will need to unplug the main pack as well as the AA pack.

As easy as that????????????

WOW!!

I was thinknig about the bind plug, but thought it wasn't a power source, type plug.

OK so to get this straight. Once all is plugged in.

Turn radio on, turn vehicle on, drive have fun... Weeeeeee!!!!!!!

Finish having fun..... Ooooohhhhh.... unplug battery pack (4 x AA, not LIPO), turn radio off. Is that it?

OK That did not work at all...

Here's what i did, took red wire from THR, turned radio on, plugged LIPO in, then plugged battery pack in bind.....

STEERING WENT BALLISTIC and winch just spat out line... vehicle would not respond to radio.

Eventually it stopped and i tried throttle, no worries, then i tried steering erratically (left and right really fast), Ballistic again.

So is there an underlying problem that may not be a BEC/External power source issue.... or have i done something wrong?

You might be right with this one, it might be an underlying issue. But its pretty hard to really work it out without seeing it/ mucking around with it myself.

It might just be a case of the radio and receiver taking a while to sync up (my dx3c takes about 5secs to full sync with the receiver). In my experience that would be why its steering/winch is going ape.
But it doesnt explain why, after it powered up and the glitching stop the steering goes ape again when you try to steer. (a dud/dieing servo would explain that)

Try it this way: Turn radio on (leave it on for a 10secs), plug pack into bind port (so your rx is powering winch and servo) then lastly plug main pack in. See what happens.

If that doesnt solve it start taking stuff out of the equation. So unplug the winch, power up and see if the steering goes ape.
If it does, plug the winch back in, and unplug the servo and see what happens.
If its still going ape, unplug esc and just power up the servo and winch with the receiver pack

If none of that works you'd have to try it with a different radio and rx to rule that out.

looks like I'm missing Q-Rock next weekend..... Sigh

I'll give everything a go tomorrow afternoon, after work, will let you know on each combo... I did try the take winch out and the steering went spazzy

but will try everything else.

Thanks for your patience and help

Sall good mate...happy to help.

I would take the servo out next and see what happens....I have a feeling that the issue could be rooted around it.

Keep an eye on the led on the receiver as well. Check to see if its on when everything is going spaz....If its not, that would be at least part of the problem - No signal for the radio to pick up.

when the steering goes beserk the LED on the receiver is off, and then flickers back on.

What I'll do this afternoon is take a video of the set up and then show you in this video what its doing so you can have a first hand view of the goings on, I'll Youtube the video and embed it here, it will assist hopefully,

anyway I'm going to work and will take my frustration out on the unsuspecting motorists of Toowoomba. God Help them.

Jayboy74 wrote:when the steering goes beserk the LED on the receiver is off, and then flickers back on.
What I'll do this afternoon is take a video of the set up and then show you in this video what its doing so you can have a first hand view of the goings on, I'll Youtube the video and embed it here, it will assist hopefully,
anyway I'm going to work and will take my frustration out on the unsuspecting motorists of Toowoomba. God Help them.

Lol....i thought all Highway cops took their frustrations out on motorists...

The Vid would help, but not really....You've pretty much given me an answer with that you said about the LED on the Rx going on.
Whats going on by the sounds of things is the servo is drawing more amps that is available from either the internal bec of the esc and even the AA pack can provide.
Cause of this its taking all the power from the rx (LED goes out) so everything else goes ape shite untill the rx gets power back and tells everything to go to neutral.

Only real way to check this is to replace the servo with another one and test again.

BINGO!!!!!

Hooked up a standard servo and no dramas at all!!!! under throttle, could turn madly and no glitch, under the AA power and returned the THR red wire back and went off the LIPO.

So it's obviously the servo.... so is this repairable??? I mean i have had it 3 months, and used it about 5 times for about 2 hours at a time, if it has to be replaced can it be a warranty job?? I bought it from the states, but am willing to chase Savoxx.

Can you repair it?

Anyway I can put in the standard servo for now for it to be driven, but am worried about its strength on course.

I will try to see if i can borrow Scott's servo as i don't think he's driving... won't tke long to fit out.

So tell me oh wise one what to do

Good to hear we worked it out.
Depends on the servo you put in there it might last for a little while at least.

I would love to have a look at it to try and work it out.
There might not be anything wrong at all. It might just be a case of it just needs a high output bec for it to work properly. I dunno exactly how many amps the AA pack would put out, but under load the voltage drop might be enough to wig it out.

I'm not sure about Savox servos but i know with Hitec you can send it back to them with proof of purchase and they will generally fix it for free + shipping costs.

Yes, now you say that the Savoxx may be asking for more power that the 4 AA's is taking and it may still require an external BEC from the battery... now BEC's are programmable (Castle) via a Castle Link, Cable (I have one of those), so if I buy an external BEC it may still be able to solve my issue is that right?

So I buy one, hook it up, then via the prgoram start at 6v and see what happens, if i get a glitch, i can then try 7v? And see what happens, in other words, I set the volts to the BEC that will alllow the right power draw for the Servo, and therefore no glitch, and therefore the servo is all good just needs more power??? Am i on the right track?

Now for the interim I'm going to source another metal geared servo, Scott says the guys at OZRC are good, can you suggest a brand that has the right price and is metal and does not need an external power draw? And from where. I'm going to make my own inquiries now. What Hitec do you like?

Bascially, if i get the truck moving for the weekend the people of Toowoomba will get a reprieve, they copped a hammering today and may not last another attack from me.


Also just thought so edited this: Reading about glitching etc people speak of the Capacitors etc, now can you see mine is it possible that it is not working thus causing it to glicth, so if i put it somehwere wlese will it get rid of my issue.... mind you I'm not sure of the reason this silver capcacitor is here for. so go easy on the terminology.



If the external BEC does not solve my issue I'll chase up Savoxx with my dilemma and see what they say, if i get no grace i'll give it to you to dissect and weave some magic on it..

Another interesting piece of this puzzle too, tryo is that Scott has the exact same set up as me as far as Servo, battery etc, yet he has had no prblems, so there is another thing thats perplexing is why is mine stuffing up but his doesn't?

Thjats what make me think is there something in the wiring that may be shorting out or something similar causing this problem.

The other thing is if i buy another metal geared servo am i still going to have the same glitching problem as now, which adds weight to the subject of another underlying problem we have missed.

Hmmm is it too early to be thinking this hard?

OK here's another line of thought but i didn't want to do it until i put it past you just so i didn't blow myslef up..

If the servo is drawing too much power from the RX, what would happen if i plug the battery in LIPO, AND the 4 x AA battery pack but did not remove the red THR wire, and allow the servo to draw from both power sources, to suit its needs.... is there a danger doing this?

Holy lot of info Batman! Alright I'll try and cover all this for you.

Firstly, its not an issue with the voltage the servo is getting, its the amps. That servo isn't rated for more that 6v, so if you get a BEC it shouldn't be set any higher than 6V (6.2v would be fine but no higher). Putting higher than recommended voltage through the servo will either make the issue worse, or totally kill the servo.
The advantage of the Castle BEC is that it has a 10amp output capacity. So if it is an issue with the servo not getting enough amps that would fix it.

So in short its doesn't need more volts, its needs more amps.


Replacement Servo: I would recommend a Hitec 645mg or 5645mg as an interim. They don't produce monster torque (about 10kg for the 645, 12kg for they 5645 or something like that), but i know for sure that they don't need a external BEC to run it. They're also fairly cheap (around $40 or something like that).

If you want cheaper, you can pick up a Towerpro 995 of ebay for less than $20. But they are hit and miss on quality. Some will last for ages but then about half of the ones I've ever ordered show up DOA.

Capacitors to solve glitches: Capacitors only solve a glitch if its caused by EMF (electro-magnetic field) Interference such as what a brushed motor produces (and power lines as well). Any glitch that is caused by EMF would effect your radio gear (you rig would drive around on its own). 2.4ghz radios are 99.9999999% immune to EMF interference.
But this issue is rooted around the servo pulling too many amps and shutting the RX down. Its not actually a "glitch" so to speak.

The Capacitor on the FX-R (silver one) is absorb and smooth any ripple current and feedback from the battery pack, 99% of ESCs have these built into the design. The FX-R doesn't, that's why its externally mounted. Its not to stop glitches. If the capacitor on the FX-r wasn't working you would know about it...The magic smoke would come out or the FX-R.


Running 2 lots of power into Rx: Do not do this....It will end in you needing to buy a new receiver and servo! Too much voltage for you rx and servo to handle. As i said, its not a volts issue - its amp draw.


Not sure why Scott doesn't have the issue, maybe his gear was made on a Wednesday, yours on Friday... But it does make me wonder.

I'm pretty sure now that you've said Scott doesn't have the same problem that there is something internally wrong with the servo (be it motor, or the control board) that's causing the big amp draw and therefore the the problem. If it was a larger issue, just replacing the servo wouldn't fix it.

You removed the suspect bit of equip. and now everything is functioning normally. That servo being the cause of the problem. But the easy way to check for sure is plug the Savox into another rig and see what happens. If everything goes Ape, you know its definitely the servo


Hope that explains it mate. If I've missed anything or its unclear let me know.