chuckk2

There may be another consideration or two worthy of mention. It has to do with what happens when a servo "stalls", due to a mechanical limit of a control surface, or a stop in the servo itself.
I generally setup servos using a exerciser, digital readout, and receiver battery. This allows me to get the linkages setup properly, and make sure that the mechanical stops are beyond the needed control surface travel.
The transmitter is then used to set the servo "span" and centering, once the receiver is installed in the A/C. Digital servos can draw quite a bit of power when "stalled" against a stop. When I have a slide switch that controls/carries receiver and servo power, I prefer to use double pole switches, and wire the poles in parallel. Finally, a visit to Radio Shack or a similar store that carries electronic parts might be made in a search for suitable capacitors to be added to the receiver and servo power. This should help with servo peak current spikes.

V2PLUS10

The Hitech spec sheet shows that a single HS-5085 can draw 3 amps on a six volt system when stalled.....

Truckracer

My Feedback: (19)

At no time in this thread has there been an indication the servos were doing anything but free running as the sticks were stirred a bit. At best the servos would be drawing a few hundred ma. of current each .... the servos were not stalled by all accounts.

Any good battery / switch can handle that kind of current and a whole lot more. All quality switches are wired with parallel contacts ... the limiting factor being the single servo style connector and cable size that connect to the battery and receiver ... more than the switch contacts. A SmartFly or ElectroDynamics HD switch has parallel connectors to the receiver and are good for at least 6A of continuous current draw. From there there are a multitude of electronic switches such as the Badger or Wolverine if you want to spend the money for them. This size of plane should not require any of these exotics though.

V2PLUS10

We can guess about this all day long. There needs to be some troubleshooting by the thread starter.

eddieC

My Feedback: (2)

Delete.

apwachholz

@truckracer (or @everyone)

Question: Am I in danger of loosing my RXconnection(a.k.a brown-out) due to the issues at hand? (and btw, why do they call it a brown out.....?)

I'm running a Spektrum DX7 with an AR6200 full range receiver, if anyone is curious. As for testing, I've done quite a bit already and I'm beginning to think that truckracer is right, I just need a beefier battery that can handle higher current demands. I'm thinking NiCd as I have a charger that canaccommodateand I don't own a charger that canaccommodateLiFe.

eddieC

My Feedback: (2)

Probably because a blackout is a total power loss, while a brownout is a partial loss.

BuschBarber

My Feedback: (2)

A Hangar 9 Current Meter can be connected between your Rx and your Rx battery or BEC. It will indicate the voltage drop and current draw on your Rx. You can momentarily stall your servos and get a sense for how much Current you are drawing and how much of a Voltage Drop you are seeing in the worst case scenario.

Truckracer

My Feedback: (19)

That would certainly answer quite a few questions.

Truckracer

My Feedback: (19)

apwachholz

The brownout question was answered by another poster. Think of a light bulb dimming rather than going dark ..... brownout was a term created by the press or the power companies during periods of low power availability back in the 60's or 70's and somehow it got applied to RC.

Many people fly 30CC, 50cc and even larger planes with 5 or more high torque servos plus the throttle servo on one good LiFe battery. I have (6) planes set up that way right now with zero problems. If all those servos were to stall, the current draw would be well over 20A but guess what ..... you never stall them so it isn't an issue. Stirring the sticks creates current draws in the 2A to 3A range ....measured on the ground. With a single 2300 MAh. A123 battery I usually see only about .1 V drop at the receiver with all servos in motion. I use about 225 to 300 MAh max. capacity from the battery on each 10 minute plus flight based on recharge requirements. I also use the same battery system in large helis and only use about 250 MAh from the battery for each flight there. The switches used are either high quality multi pole slide types such as the types listed in an earlier post or in one case, I have a fancy electronic switch. Voltage drop across these switches is hardly measureable and if a voltage drop did develop, the switch would be replaced asap.

On 100cc and above planes I just add an additional battery and switch. The point here is that you don't need a bunch of fancy equipment, regulators, etc. .... you just need good quality batteries and switches that are capable of handling the current requirements of your servos. Your servos are not power hogs like the ones that would be typical in larger planes or helis.

If you are thinking about a new battery, you can go with Nixx chemistry but I would highly recommend one of the LiFe types with an absolute minimum of a 10C rating. Good chargers are available at reasonable prices so that really isn't an excuse not to use them. I am especially partial to A123 batteries but I certainly see many of the soft side LiFe batteries being used everyday with great success.

As mentioned by others, there is some great reading about the various battery types and charging at NOBS batteries .... that is also listed under Hangtime Hobbies. NOBS is not a cheap source of batteries but the quality is excellent and the product is reliable. Wild Hare RC use to offer a starter set with a A123 battery and charger for a reasonable price. You might check with them also for info and availability. There are many other sources of excellent LiFe batteries so I'm not trying to push you in any one direction.

Its too bad you are not close to one of the excellent posters here in this forum. Many people could diagnose and resolve your problem in very short order.

3136

I would get a servo lead, plug it into a spare channel on the receiver and strip the pos and neg wires and hook them up to a multimeter.
Flip all your controls around and look at the voltage.
If it drops too much you need to supply more current.
To test that theory, try running just one servo as earlier stated, and look at the comparative effect.
I'm not an electrical genius, but that reasoning sounds solid to me. (correct me if I'm wrong)

Truckracer

My Feedback: (19)

You are 100% correct. That would be an excellent test if the OP has the meter.

modeltronics

My Feedback: (27)

I’ve been reading this thread since it started and have made some comments in it. I would like to make a couple more but I do not want to start an argument.

Using a voltwatch or a meter does not give you enough information. During the first less than 10 milliseconds that a servo starts to move there is a current inrush. The voltwatch or most meters are not fast enough to catch the current inrush and the voltage drop caused by the inrush. Even if they were fast enough your eyes would never catch it. It takes a storage scope to see this. ( and I know not everyone has a storage scope) Even though you cannot see this fast voltage drop it can be enough to brown out and reset your receiver. I did look at the voltmagic mentioned early in this thread and it is a much more useful device than a voltwatch.

Also mentioned in this thread is a current meter. I would put that in the same case as using the voltwatch or voltmeter. It is just not fast enough to see what is going on. To see the peak current it takes a storage scope with a current probe.

It is my opinion that some of the devices sold make you feel good but do not tell the entire story.

Next is using NiMh batteries. The internal resistance of NiMh batteries is not a constant. It goes up as the current demand from them goes up. Be very careful when looking at the specifications of NiMh batteries. As the internal resistance goes up with the current draw so does the voltage drop. The internal resistance is not a linear function of current draw. I have worked in engineering with devices that use NiMh batteries and it took a lot of testing to find this out.

This is just my 2 cents worth.
Pete

tomfiorentino

Oh boy....I would run for cover on that comment.

Tom

eddieC

My Feedback: (2)

I think that's a very believable statement.

I think taking a data-logger or recording watt-meter aloft would be a big eye-opener in many cases. Peak loads, especially for 3D helis and planes, could be surprising.

tomfiorentino

At the end of the day, the information has to be relevent. From everything I understand about this subject, we need information about voltage drops that sustain themselves over a period of time that is long to become problematic for our application.

The on-board voltage devices are sensitive enough to be in front of what our receivers see so that they provide early enough detection of problems.

They are a perfectly matched solution to the presented problem.

I don't know the first thing about a storage scope, but I know I don't need one!

Tom

modeltronics

My Feedback: (27)

Hi Tom
Take a voltage source and make it dip below the reset point of your receiver for 10 miliseconds (or even 100 miliseconds) while looking at it with a standard volt meter or a voltwatch. I can bet I know what you will see…nothing. I know what your receiver will see… a low enough voltage to reset it in some cases. Now look at it with a storage scope and you will see the voltage drop.
Pete

tomfiorentino

Hey Pete,

I get that...but does it really matter? I mean, my point is take that same low voltage level that would cause the receiver to tank and tell me that your battery wasn't in the cemetery anyway! Said another way, you have a bigger problem than a brownout...

Also, I am interested in the 100 millisecond comment. Too often we just talk about a voltage level threshold. But there has to be a duration to it. So, ok, the voltmagics of the world will see voltage dips that the receiver wont see, and your scope will see voltage dips that the voltmagic wont even see. But neither of them are seen by the receiver.

I know guys have tested this and it would be good to just have published data by the manufacturer. One of my JR receivers instruction sheet says keep voltage at 4.8 vols or above at all times. Why? Because it browns out at 4.7 volts? No...

Tell me a voltage level of x.xx for a period of xx seconds initiates brownout.

But again, its mostly an academic argument anyway because the battery is smoked anyway...running that thing too low!

Would be interesting if someone could publish some stats for voltage dip and duration in combination altough it is different for all receivers I would imagine.

Thanks for the post!

Tom

modeltronics

My Feedback: (27)

Tom
Good point and I agree with you that it would be nice to see some specs published. I do have the equipment to make these measurments but don't have the time right now. It might make a good winter project to set this up on the bench to find the time and voltage to reset different receivers.

Pete

Truckracer

My Feedback: (19)

All the above is very good info but lets look at the OP's equipment once again. Though his servos are digital, they are relatively low torque mini sport servos. This is not some giant scale aircraft with the latest and greatest, whiz bang high torque servos. High current peaks and extreme voltage excursions should just not exist if he has even close to an adequate power source. I have the equipment and the experience (decades worth) to operate it, I have published info on connector and cable losses, all kinds of switches, etc. but almost none of that applies here. A good simple switch and battery should solve this OP's problem ..... period.

Rodney

The Voltwatch is almost (notenly almost) as good as an oscilloscope as it responds to the transients quite well. That is one of the good things about the Voltwatch, if you see it flickering into the red you know you have some voltage transient problems. This can be a forewarning of possible brown outs if you are using 2.4GHz systems. That flicker into the red is a very reliable WARNING that you are getting some very low negative voltage transients at the point the Voltwatch is connected. Somewhere you are getting voltage drops; could be high battery internal impedance, to small a gage wireing, faulty switch but something definitely dropping that voltage for an instant or two. It is not a faulty Voltwatch.

tomfiorentino

Bravo, bravo! So don't ignore the message.

Actually, the OP tried a different voltwatch in the same airframe and got the same results.

Agree...not the voltwatch.

Tom

3136

I know it's kind of masking the problem but would a capacitor alleviate the issue?

eddieC

My Feedback: (2)

Not hardly. If you have some specific data beyond a Mk 1 eyeball, then let's see. Having had a voltwatch fail in a G-23 gas heli with a 1700 ma Nicad pack using analog servos, I can attest they can be flawed and a costly event when they do. I've moved past them to various watt-meters and a Sentry ESV that puts a load on the pack. Much better options out there than a row of flickering LED eye candy. [X(]

Approach Control

My Feedback: (44)

Go to Harbor Freight if u have one close by and buy a $4.00 digital
Volt meter (modiy your connectors so u will have the proper connector and u can load test it using a y harness to tour servos