Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[NobbySideways]

Apparently Tunigy do a Voltage Protector, which to me looks like a 3300uf capacitor soldered directly to a servo plug... 


No bearing in mind I could make one of these with parts under the desk for free, is it actually needed? I should imagine some models are capable of spiking current draw quite heavily, but has anyone actually had it happen to the extent where control is lost for a sec? Bear in mind I've not done much with RC, I'm very inexperienced.


https://dalewoodmodels.co.uk/product/turnigy-voltage-protector-helps-to-eliminate-brown-outs/

[Umi_Ryuzuki]

Setting up and Running a Tito Neri for a client, I had power issues.
The high torque servos would pull a lot of amps when working against the prop rotation through
the Z-drives. That additional power draw would cause the boat to drop power and reset the receiver.
I worked around the issue by running the power cables for the two servo directly to the power bar, and running only the signal wire back to the receiver.
It worked fine after that, and placed third in a maneuvering competition.


 


Not sure if that capacitor would help or not, but I see how it might...

[inertia]

As a manufacturer then at a total cost to me of perhaps 40p I would say it's a very necessary item.............. 
If I were a customer then I'd wait until all other possibilities had been exhausted and then fit one - maybe. 

'Brownout' happens where the voltage supplied to the receiver falls below its minimum operating level and then suddenly jumps back up again, causing the receiver to reboot or reset itself (as if you'd switched it off and on again quickly). Its most frequent cause is a BEC regulator which in turn falls below its minimum level because the main battery drops in voltage. Usual cause is a stalled motor, battery failure or an electrical short circuit. If it bothers you then see what happens when you switch the Rx off and back on again very quickly. It might be a problem for a RC helicopter but unlikely for a boat. I've never used one or seen one fitted anywhere.

Caveat emptor (but please yourself).

DM

[malcolmfrary]

It can't do anything to save any battery, but it might make up for some deficiencies in a battery that was marginal in current delivery ability or mildly under-rated wiring.
The link only claims that it "helps" to eliminate brown-outs, not that it actually cures them.  That's where the emptor should start caveating.  Having said that, it shouldn't do much harm.

[Andyn]

Brownout protection? See here..


http://bit.ly/1J8lWyI

[Martin (Admin)]

That's Brownout  not..... something else! 

[Time Bandit]

I bet around 80% of all RC plane crashes happen due to brown outs or letīs call it insufficient receiver power.
2A BEC from ESC and 6 large digital servos, thatīs what I see sometimes 

In my planes I usually separate the BECīs for the receiver and the servos and/or solder 100ĩF caps into the servo wires.
For slow boats I donīt see the necessity to do it if you have no "reglar" brown outs, but for faster ones itīs definetly a must have for me.
20 pounds at 70mph are a deadly weapon if uncontrollable for 4s and itīs sometimes unbelievable what you see here at the lake. "Polished" 2000€ 10 KW powertrain in the boat but a 3$ BEC  running a 200€ high power servo.

Iīd say: avoid the root cause, get a proper BEC system (those high amp 10A? Turnigyīs are pretty good, they even have a low ripple at the output, but are also only capable of 5A or so) or use a receiver battery. No need for additional caps.

With some servos (e.g. those cheap MG996 with metal gear) itīs nice to have a cap in the wire since those draw extremely high currents for a few milliseconds.

[inertia]

"BEC" again.
Unless it is absolutely unavoidable my advice would always be to use a separate receiver pack in a model boat. It's not even as if they were expensive; check out the price of a 2900maH NiMH pack against a high-current UBEC.
Soap box away.
DM

[tigertiger]

That makes absolute sense DM.
I can understand the weight issues for extra batts for planes, but it is a consideration in very very few boats.

[inertia]

I just checked on a popular Far East supplier's UK warehouse website and found a 2300maH 4.8v NiMH pack at Ģ3.77 and a 8A UBEC at Ģ10.52.
On Umi's point, it's long been a practice for high-torque yacht winch servos to be run from their own battery pack - frequently 6 or even 7.2v. I don't see the need for digital servos in most model boats but if you do fit them then a separate battery pack for them might be a very good investment. You need to ensure a smooth and uninterrupted power supply for the receiver to avoid brown-outs.
DM

[NFMike]

That makes absolute sense DM.
I can understand the weight issues for extra batts for planes, but it is a consideration in very very few boats.

True, but it's inconvenient having a separate battery to charge ... probably with a different charger as well.

[NobbySideways]

I do seem to have a habit of opening cans of worms... 


I can understand the logic of a separate receiver battery pack. I don't mind a bit more weight up front... probably a good idea... 

[Martin (Admin)]

Throwing my hat in the ring, BEC every time, it's just less items to worry about.

Lets start a poll!

[JimG]

A separate receiver pack is not proof against 'brownout'. When this first came up (early Spectrum sets which took several seconds to reboot) it was found that 4.8V AA NiMhs could not provide the current for high power servos without dropping the voltage below the minimum for the Rx. The recommendation was to use a 6V supply for these or larger cells which could cope with the current demands. (Other makes had a lower minimum voltage and did not suffer this.) Newer Spectrum gear does reboot quicker now so not so affected.
I see no reason for not using a BEC to provide Rx power as long as you make sure it has a high enough current rating. I fly a jet using a BEC from 2 LiPos to drive 6 high power digital servos. I have no intention of using a separate Rx NiMh pack. (The BEC is capable of 10A and will pick the better of the two packs to provide reliable power.
If the ESC you are using has a suitable BEC then use it, if the boat can carry more weight then fit a larger battery. If you are using a brushless system the BEC is probably capable of providing power better than an AA battery. One of the lessons from planes is that the switch from the Rx battery is one of the least reliable parts of the circuit.

Jim

[sparkey]

  I always use a separate battery for RX having suffered a brownout on my very old Sea Queen which hit the concrete bank rather hard and fast,the damage to the old lady was considerable and heart breaking,so now all my boats RX have their own supply, like it is not likely that most boats are short of space or weight is a problem,so play it safe guys and do as I do or one of your pride and joy's could end up wrecked like mine,high capacity rx batteries are not that expensive (about a tenner)when hundreds of pounds of your boat is involved,some time ago I bought a box of batteries from an old guy who was going into a home and didn't have the room, there were some 11.1v 2200ma lipo tx batteries which I use with a voltage regulator from Tornigy 5v 4amp output,works well and last for ages,there is about a hundred batteries in the box and I am slowly using them all up, recycling you might call it and has saved me a fortune,Ray.        

[Calimero]

I'm facing those very issues with my Mtronik ESC and my way-to-powerful-and-fast rudder servo on my Odin tug. Current draw from the servo is way too high for the Mtronik's BEC (I was using a Graupner ESC before with a marginally better). At best the small controller for the navlights resets itself. At worst the RX goes berserk with the rudder twitching and of course no power.


Anyway I'm with Martin: BEC all the way. I have a 5V/5A standalone BEC which will tap right in the main batteries and power the ESC, servos and such.


And I'm switching to my new TX which let's me set servo speed from the TX (rate of change, actually) so that my rudder will behave a bit closer to reality and draw much less current.

[NobbySideways]

Could the poll differentiate between built in BEC and a seperate BEC?

[inertia]

BEC is the cause of more electrical problems for - and questions from - beginners than anything else. Just read some of the old threads in this forum and you'll see what I mean. If you know what you're doing then they are not a problem - but you are in the minority, believe me.
I have nothing against them for any idealogical reasons. I do use a BEC brushless speed controller in my small Huntsman, but it's only running a tiny 2G4 receiver and one Hitec HS81 servo and there is a low-voltage alarm and cutoff (if only to protect the LiPo pack). However when you start using high-current digital servos, for whatever reason, then whatever sort of BEC device you have will drain significant levels of power from your main motor power supply, reduce run times and increase the risk of receiver power failure. That would point me increasingly towards fitting a separate, high-capacity receiver power supply and not just a fatter UBEC.
We can dismiss RC aircraft and helicopters from this argument because they have completely different requirements from most model boats (except perhaps fast-electrics). As for 'inconvenient' - sorry but for as long as you have to go into the workshop and set up a charger for your main battery and perhaps the transmitter then that argument is tosh.
Finally I don't believe there is any point in having a poll unless the type and size of model is considered, because it's not an absolute 'for' or 'against' issue. I'd not consider a separate Rx battery in a 1/16 scale Huntsman but I wouldn't run the Rx from a BEC in a 'Parat', with four digital servos for the two VS drives and multiple other servos, switches, pumps and lights.
Dave M

[NFMike]

... there were some 11.1v 2200ma lipo tx batteries which I use with a voltage regulator from Tornigy 5v 4amp output,

That is basically a BEC then. If you exceed 4A by much it'll brown out.

[Martin (Admin)]

Could the poll differentiate between built in BEC and a separate BEC?

Bit late now!   

[inertia]

That is basically a BEC then.

Not strictly. The way I read it no Battery was actually Eliminated from the Circuit; the regulator was used simply to reduce a separate Rx power supply from 11.1v to 5v. No doubt Ray will correct me if I'm wrong. 
DM

(BTW I wasn't the one who polled as hating BEC's!)

[Martin (Admin)]

(BTW I wasn't the one who polled as hating BEC's!)

             

[inertia]

     

[Time Bandit]

BEC is the cause of more electrical problems for - and questions from - beginners than anything else. Just read some of the old threads in this forum and you'll see what I mean. If you know what you're doing then they are not a problem - but you are in the minority, believe me.

Totally agreed.
Thatīs my experience as well.
At least 80% of the people you meet at the lake (no matter if beginner or not) are totally unaware of basic electr(on)ical  facts.
This includes the usage of resistors with LED, you wouldnīt believe how much people still believe that a voltage regulator set to the forward voltage of the diode alone is a good power source for LED  and then wonder why the "unbreakable" LED go up in smoke after a few hours.

A BEC is a nice thing, I personally use them in every boat (itīs pure lazyness that I donīt want to charge another batt), but a very dangerous item since they are less "forgiving" than a separate battery and most of them are totally overrated regarding their amps.

[NFMike]

Not strictly. The way I read it no Battery was actually Eliminated from the Circuit; the regulator was used simply to reduce a separate Rx power supply from 11.1v to 5v. No doubt Ray will correct me if I'm wrong. 

Indeed, it hasn't eliminated a battery.
However, my understanding of the brownout problem is that a BEC (aka Voltage Regulator in most cases) has limited current capacity compared to a rechargeable battery.
So introducing a VR between your battery and receiver/servos has the same potential issues as using a 'BEC' (VR).