The whole powerbox issue

[jjjvr]

Hi, maybe someone could put some light on the whole issue of introducing a powerbox into large scale aircraft. I am currently building my first 1/3 scale a/c, the cap 580 from greatplanes so is sort of new to this. Bottomline is that yes I suppose it would be the best to just put in an emcotec or equivalent and get it over with but is it really neccessary. I am running 6 hitec 5645 digitals, one 5955 and two standards. Another options seems like the smartfly super regulator, but as far as I am concerned that still places the demand for amps through your receiver. Therefore the question, when does is become neccessary to introduce a powerbox, and what is the best value for money?

Thanks
Johan

[TheTank]

I know of several 40% airplanes that run all servos directly through one reciever, without issues, although I would not do this myself. I currently have 2-35% airplanes with all servos directly into one reciever without problems, they also have dual power supplies going into them as well. I have had zero issues with this setup running a JR Rx. I suppose you could use an Emcotec mini if you liked, or something like a Smart-Fly power expander if you were worried about the amp draw through the reciever. On my 40% Yak, I do run one RX and an Emcotec DSPI-RV LDO box with great results. Without having to run any y-harnesses, each servo gets its own power source, and an amplied, rf-free signal. On a 35% airplane, I really think its up to the user as to what you want to do. But you will be fine running it all through one RX.

[b0Bro']

I just bought my first big bird (Second Hand). It has been running for years on one reciever no problems. Now that i have it I just feel that ive invested so much money into it, I will take the safe side and take all the load off the reciever with a power expander. Who knows, it could be on its last breaths now.

Personaly it just feels safer to me, altough it was probably not needed.

[RollingHarrier]

I have a CHP 34% Extra running all digital servos, dual NiMH batteries into the one running through the Futaba G3 receiver.
On my two 40%s I'm using dual Futaba 149 receivers that split the airplane right down the middle. All servos are digitals. I run it this way for redundancy.
I've been flying with these kinds of setups for years.
There are two things to be aware of when setting up a bird, signal and voltage degeredation to the servos. What you need to do is use twisted pair 22 guage wire on anything 2 feet or longer ( same concept behind telephone wires). If you know how, you can make them yourself or I think you can get them prebuilt from Airwild.
The receivers can handle the current. Eloy (HighFlight magazine) did a test on a receiver where he passed 8 amps thru a receiver before the traces started to lift. He even showed you how to solder wires across the buss in case you where still worried.
I also use Deans connectors between the receiver and the servos instead of the standard connectors. This way I know my servos are getting all of the current they need with no or minimal connector loss. Deans are also great for plugging and unplugging repeatedly. I've worn out (or broke) standard connectors after a few hundred cycles.
Hope this helps.
Jim

[jmiracle]

Here's my take on this....in a 33-35%, you're still mostly likely running 2 batts to the Rx....and if you use Li-ion's, you'll need 2 regs for the batts. A GOOD reg from Fromeco, Duralite, SmartFly, ect is going to weigh somewhere around 1.5oz - 2oz. with switch and wiring and cost about $40-$60. So your basic power system will weigh 3-4oz and cost $100-$120.

The Emcotec mini replaces both regs, plus offers a bunch more safety features....helps eliminate wye's....takes the power load off the Rx....cleans and amplifies the signal to the servos. The mini doesn't weigh any more than 2 regs....you can turn the entire plane on with one switch....and it helps clean up the wiring rats nest inside your plane. At $200, it will cost another $80-$100 over a basic li-ion/reg setup.

I won't build a 35%'er without one.......just my $.02....

[Kiwi]

JJJVR,

I will try to be objective here and not stray too much from your question.

The first myth with receivers is people think that the current draw to your servos goes through it. Thats actually false as the positive and negative source to you servos is on a bus. Basically your battery packs are connected directly to your servos.

If you have an old dead rx pull it apart and you will see what I mean. I have seen receivers with 20 amps load on them and they hold up. In fact a 40% model with good digital servos can easily load your battery packs up to 10 or 12 amps for a brief moment and easily hold an 8 amp load in some situations.

So whats the sense of a power system then if your receiver can take all that load and not melt.

Its simple. The current draw for your servos is not the issue. Voltage is the heart and crux of all rx issues. The problem comes along when the voltage drops under those sudden load changes. When that happens the signal seen by each servo gets a false pulse so the servo thinks the radio told it to do something. That false signal can become an issue if it is strong enough to generate a continuos voltage variation. Often what you see is jittering servos. Sometimes very minor, sometimes extreme flutter like movements.

So what does a power board do.

Principally it gives your receiver a clean 5 volt feed that is isolated from the servo deliver voltage. In the Power Expander for example the rx sees 5 volts. The servos can be running as high as 6,5 or so.

Any current and voltage fluctuation is all kept away from the radio part of your model. Its like two seperate circuits.

The other advantage of all the power systems is the rx signal to your servo is amplified and filtered so it gets a really clean and constant signal. Thus your servos go where you point them and not where Murphy decides.

Some power systems will even lock out a short circuit so if you have a servo burn up for some reason it removes current from it and hopefully you bring your birdy home with one servo less. Of course if that servo locks over then you need to be Billy Hemple or someone in that league to fly your one winged plane back home.

In breif. 35% or bigger planes I just wont fly without a power system. In my humble opinion the planes fly better, are less susceptable to onboard glitching and signal degredation caused by long servo wires and inbuilt RF.

In fact I have recently tested a new 14MZ smart-Fly power expander and the antenna down range test tripled. It went from 50 paces to nearly 170. That I will willingly show to anyone who doubts me on that. I am not selling smart-fly on this site but that guys is a fact.

So if you have a $3000 plane and dont want to put $200 more into it to just clean up the antique simple rx systen then thats a choice and there are guys with equipment in both camps. To me its a little bit of insurance and hopefully makes my planes safer.

Hope some of this jibberish makes sense guys. I'm no electronics guru and work on the theory that if you cant see it dont play with it. That is why I like nuts and bolts and not Lectricity.

Kiwi

[b0Bro']

If thats true, i feel better about my purchase!

[aviti]

Kiwi - I think your advice is sound but I also don't think on a 35% plane that a power system is a necessity. Why you ask? I've been running 9 servos out of my one receiver for over a year. I have dual 2400 Li-ions with Smart-Fly regs. Not one issue to date. As far as range goes, I took my TX out completely and with my engine running, I got to 300 feet and still no glitch.

Not saying there aren't benefits to the power systems for a 35%, but just pointing out that a lot of people run perfectly fine without them. To each his own.

[storklappe]

Kiwi,

Can you run the Smart-Fly with two receivers?

[b0Bro']

	Quote: Originally Posted by storklappe
	Kiwi, Can you run the Smart-Fly with two receivers?

Yes you can. Just need two boards.

[high alpha]

The power box has many advantages.A clean set up is just one of many reasons to use one.Hope this helps.

[Wayne]

Is it needed? No.
Lots of Giant scale planes flying around safely without them. That proves its not "needed"
I dont think you'll find anyone who has spent money on one saying they think its not needed. Its the nature of the hobby. Nobody wants to admit they spent money when maybe they didnt have to. I completely understand that.

Does it do some cool stuff? Absolutely.
Keep in mind that there are several ways to accomplish what we are all looking for. Safe, giant scale flying. If you feel one of these devices helps you achieve that, go for it.
is it "Needed" No.

FWIW, all my planes from 28% to 42% run the same set up.
Single RX. Dual Li-ions, Dual Switches, and Matchboxes to handle to extra servos on the larger stuff.