Hammbone

My Feedback: (309)

Like I said before, the reason to use a Power Expander is because a standard connector has its limits. You recognize that 22g wire has its limits, but you don't recognize that a standard connector has its limits.

Jim

Tired Old Man

My Feedback: (1)

But I do recognize that there are limits. Recall that I've even tested them. As far as 22 ga wire is concerned I've even had the calcs done by a couple of electrical engineers to see how much and how far it can carry and still provide a given voltage and amperage, with and without a connector in the line somewhere. That's under 5' to deliver a continuous 2 amps with an initial 6.5v input btw. On larger models any connector far from the receiver/power source would probably never be able to experience 3 amps. Want to test your connectors? Easy. Grab an amp meter and connect a servo up to it. Stall the servo so it draws 3 amps or more. Hold it there for a while. Watch and feel the connector.

You see, that's the problem. I know what can and can't be done, and recognize that with correct wire sizing and limiting the number of connectors much of what we buy to put in our planes is absolutely unneccessary. It wasn't all that long ago giant scale planes were flown with large wing spans, multiple gas engines equipped with magnetos, electric retracts, numerous servos, with gobs of wiring and none of the stuff on the market today was available. All we used were larger batteries. Guess what? Those planes flew very well and without issue. Still do, and would if another was built.

Spend your money where you want to and enjoy. I'll admit that all the new equipment makes it a lot easier for the average person to put one together, but man, what a price to pay. We are much too easily sold on advertising.

Bob_S

I think that when you start using more than 1 servo per port on the receiver you should start considering a power expander. For sure if you are talking about more than 2 servos per port. It doesn't need to be anything fancy. In fact you can use something like this. http://www.servocity.com/html/servo_power_boards.html

Hammbone

My Feedback: (309)

Yeah, $100 for a Power Exoander. What a price to pay..........

Jim

OldRookie

My Feedback: (13)

Bob,

I like that idea. Less than $20.00, and you can run a heavy gage wire to power board, and are able to use a Deans connector from your switch. That is about all I am looking for. All of the other circuitry in the SmartFly Power Expander, just leaves another point of failure.
Has anyone here used this power board?

Greg

Bob_S

One board can run two channels with 3 servos each or 4 channels with 2 servos each. You just need to bridge the signal paths together for the servos you want ganged.

OldRookie

My Feedback: (13)

Bob S,

Another good idea, good information.

Thanks again,
Greg

Tony Hallo

Here's JR's answer for the most demanding applications. [link]http://www.jrradios.com/Products/Default.aspx?ProdID=JRPR922[/link]
The radio manufactures finally are getting on the power expander train. At $240, about the same price as a receiver and power expander. Features robust power buss, this one might handle 60 amps, I doubt the standard receiver will.

altavillan

My Feedback: (1)

As of right now there is only two reasons I use a power expander.
1. To allow Hitech servos to work with the new Fut 6014 rx.
2. I believe SF makes a quality product that does what it says... Provide a clean signal to the servos.
The SF expander and 6014 rx is on a 35% plane with a bunch of 5955's. There's a ganged rudder that will go nuts with out the expander.
Soldering up multiple connectors to the batteries to draw straight from the switch's/batteries is how my 30% ers work with the 617 rx. The 617 rx weighs less than .5 oz making it kinda tiny for running a 30% plane but it does just fine since no real power draw is coming off it's buss bar.
So I vote yes and no.

Tired Old Man

My Feedback: (1)

The proof of a 60 amp bus in the receiver was turned into a statement of fact a couple of years ago. The printed text is in a Scale Aerobatics column of Model Aviation written by Mike Hurley. I think the first name is Mike, could be wrong on that part. Last name is correct for certain. You get to do the looking on your own.

Taildragger726

I wish JR would have made multiple outlets for ganged servos. A major issue(with me) with two, three or four servos per surface.

Tony Hallo

[link]http://www.jrradios.com/Products/Default.aspx?ProdID=JRPR1222[/link]
They offer a 12 channel however you will need the 12 channel transmitter!!! I expect other manufacturers to follow suit. Multiple outlets can't be far off either, of couse this is only my opinion. Planes are getting bigger, jets are faster, servo output is up, it was only a matter of time. The standard plugs are at the design limit with the current servo power demands, I expect the next increase in output will require seperate power supply to the servo.

RTK

My Feedback: (1)

I have set up 35+% planes with and without power expanders, and if done correctly, they both work fine. I like the the smart-fly power expanders, priced right too. When paired with the new A123 batteries they make a clean install.

Altivillan-You can send those servos into Hitec and they will up date them to run on the lower signal voltage of some Futaba receivers.

The attached picture is one of my latest planes, next one won't have Li-poly.

altavillan

My Feedback: (1)

I still wouldn't trust the Futaba 6014 to run Hitech servos with out an expander. So I see no reason to send them in. They work fine in the 617 and 607.

RTK

My Feedback: (1)

My 5955's work fine with the 6014, or at least so far

Tired Old Man

My Feedback: (1)

So there you have it. The original question was to need a Power Expander or not.

The answer is ambiguous. Some feel they need it, some have never needed it. I suppose it all lies in the talents and knowledge of the individual setting up a plane. Those newer to giants may find them more necessary than those that have been setting up longer. They would likely make the process easier for many in either case.

MIXMASTER

My Feedback: (15)

Oh boy, here I am starting to build my 1st 33% Yak/3W80 and this is becoming an issue before the maiden! I dont like to waste money, but I want to be safe & happy with my plane. I have an old Fluke DVM, I think I could use it to do the current test on a stalled servo on the bench. If I remember my basic electronics right, I connect the leads in series w/return(black) lead from the servo. I'm using Futaba 7C FASST radio, I seem to remember e-mailing Futaba about their receiver max current specs & 10A. comes to mind. Sounds low, conservative number for todays digis & 3-D planes. Also, TBM has some notes stating that 1amp draw is typical with a single digital servo, so 7 digis on a 33% could demand 7amps total, would that be a safe estimate,worst case? Any way, I'm looking at it from different angles too, I'm spending several grand on a plane, another $100-$150 shouldnt be a big deal, specially if it gives me an extra safety factor along with performance. On the other hand, I still dont want to waste $$$ if not necessary. I know I sound like I'm wavering, I am!!! Will have to evaluate several things & decide. I know one guy flying 35% 3-D planes without P.E. , he uses the programmer & match boxes, never had a problem. Then another guy swears the P.E. is a must, not safe to do it any other way, he has never had a problem either. One thing I got from this post, the P.E. is not a replacement for proper servo set-ups, you better get that right or watch your batteries drop.

Zeeb

My Feedback: (41)

Just a couple of thoughts;

I was told by a guy who's been doing RC stuff for years that one might figure on 1 amp per 100 oz. of torque on a servo. If one looks at the specs for the high torque servos, that number is really close. Now granted, they would not pull that kind of power in most situations, but can if needed. The other caveat is that if they get binding problems with the linkage, they can actually draw more current....

Now as for the buss in certain popular rx's; IIRC Bax over on the Futaba support forum indicated the FASST rx's have an 8 amp continous rating on the buss. I don't recall if I've ever seen anything other than that figure for the Futaba, or what the burst capability might be.

The Spektrum/JR stuff is 35 amp with a 50 amp burst capability.

So as to which way to go for your power setup?

Basically you're now down to the place we all come to at some point in the hobby; you can do all the research you want on specs and other user's opinions but at some point, you're just gonna have to decide what you think will work best for you....

MIXMASTER

My Feedback: (15)

So if I only needed 2 or 3 channels w/ 2 servos each, I would have to solder the pins together as needed?

MIXMASTER

My Feedback: (15)

Thats pretty close to what I recall from Futaba, only 10A. max is what I remember. Thats a huge difference from Spectrum & JR receivers mentioned above. Even 10A. sounds like it would be pushing it with a 33%, 4 aileron servos(2 per channel)2 on rudder, one on each elevator. The Servocity board looks like it would work for my 33%, not sure if I would have to do a lot of wiring/soldering though, the web site only gives you "kit" price or "assembled", doesnt say how its assembled, i.e. can you specify 2 servos/channel or 3/channel??

Steve

My Feedback: (54)

My expiereance has been to use a power expander if I'm using less than a 9 channel reciever. I'm now using 14 channel recievers and have had no need for the power expanders. I'm using dual LiIon batteries on regs and have never had a power issue, or stall. I also use the HD Futaba Switches. I do a lot of 3D, high G flying like wall, parachutes, blenders, rolling hariers, ect. I"m using Hitec 5955's and 7955's. Two per aileron, two on the rudder on a couple of models.

OldRookie

My Feedback: (13)

Zeeb,

So you are saying that the complete line of Spektrum/JR receivers has a 35 amp continuous capacity, and a 50 amp burst capacity?

Greg

jimsyak54

it's pretty ridiculous considering the literally hundreds of airplanes that are flying without power expanders to conclude that anyone has to have one. power expanders came on the scene several years after 35% and 40% airplanes were common, and they were not in response to a specifically identified problem, but to a perceived problem. billy hempel was flying a 50% edge without a power expander because one had yet to be invented. No one has been able to prove their necessity, just like the folks that said years ago that a single receiver could not handle servos loads of ganged servos - a position that has been yet to be validated or proven, yet is still repeated. a friend of mine says that if you feel better having one, then buy one, and if you know you don't need one, fine. but the idea that you have to have one is bunk, and the empirical evidence is overwhelming. btw, mfrs have it in their interests to be very conservative in what they publish, and I used to regulary blow 5 amps through my connectors when i was fast charging a 5000 Mah pack, and of course they worked just fine.

OldRookie

My Feedback: (13)

Mixmaster,

I contacted Servo City on their Servo Power Board. They said you have to solder the pins in, and it was a simple process.
I like the idea of the Servo Power Board, and most likely purchase one. For $18.00 it does what I would want from a power expander, at one fourth or less the cost of a power expander.

http://www.servocity.com/html/servo_power_boards.html

Greg

Zeeb

My Feedback: (41)

I haven't dug into the specs for the AR7000's and below as I don't see an issue there when I run the 9 channel rx's or above on my gassers. The AR7000's may have the larger buss as they are very nearly an identical size with the AR9000's, but you'll need to dig into that if you're interested. I know folks do run those in gassers, but all I run 'em in is a couple of glow models I keep around. All the 9 channel and above rx's, AR9000/JR R921, AR9100/JR R922, JR R1221 and the JR R1222 all have the same buss capability. I'm not sure if they use the exact same buss (part number) in all of those, but it would seem to make sense that the same buss is used in all the rx's from a manufacturing standpoint.

The big PowerSafe rx's with the dual 16g. input wires and built in fail on softswitch, AR9100/R922 and R1222, do not have any rx's inside the main unit like all the others since the engineers thought it might be best to move them away from that big power buss. That's why all those can use 4 satellite rx's.

Just keep in mind that the current (sic...) bottleneck in the power systems now, is the standard size servo connectors with their tiny pins. Those are only good for about 3 to 4 amps (depending on whose test results you believe and the quality of those connectors) continuous and will burst to 6 amps without much problem. They will get slightly warm at the 3.5 to 4 amp continuous rate, or at least the ones I use do...