Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Can my reciver handel the power to 5 hitec 5955 or do i need a powerbox

Daniel i sweden

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

your RX will handle them just fine.......

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Yes. I have run up to 10 JR8611 and 9 Futaba 9152 servos through a single R149DP without a problem.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Personally I think these powerboxes are just another unneccessary well marketed product :)




Flame away.. I know I am not the only one thinking it :D

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Well I don't really agree with that but only 5 servos in a 9 channel receiver should be fine.
In my 33% setup I use 3x5955 and 4x5945 plus throttle and choke. Worked perfect since beginning 2 years ago.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Powerboxes offer far more than just current handling! Things like voltage regulation, glitch suppression or elimination, multi servo per channel functionality, trimming, servo matching, voltage monitoring as well as other stuff, all part and parcel of some of the powerboxes out there. It really comes down to comfort level and budget!

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

it also adds another point of failure

voltage regulation ? - not really needed unless you have lipos (if you must use lipos can just buy a reg)
glitch suppression or elimination ? not really sure how - if you have a glitch there is a reason
multi servo per channel functionality, trimming, servo matching ? - matchbox / equalizer.. although personally I can do that in linkage
voltage monitoring - rather use a load meter to put a high load and get a real reading


It really comes down to comfort level and budget! - Like I said .. well marketed.. made a lot of people think they need them :)

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

No problems with the current handling ability of the 149 RX and five high power servos.

The real problem in this case is the capability of the power source/distribution system. What type/size of batteries are proposed? Heavy duty, quality gold plated extensions, connectors and switches are a pre-requisite for digital servos. The goal is to minimize electrical losses and failure points, so accurate length extensions and leads are preferred with minimal connector counts too.

Servo interfaces and or Powerboxes serve a purpose and are a means to an end. There are distinct advantages IMO, especially when you can eliminate several ancillary devices with fail-safe modes, truly redundant isolated power routing, control signal amplification and isolation and more. Do we really need these devices, NOT. But in the scheme of things they replace multiple other devices, minimize electrical losses and provide a robust power distribution system that is second to none.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Well I am sure there are cases where this would be a benefit, such as a high-end 40%er with 2 or 3 rudder servos, 6 al. servos and 4 el. servos.. or something like that sure.

However you can build NiMH battery systems that don't need any special gear and will still put up 40+ Amps if needed and only weigh 4-6 oz. more then a lipo system.

I don't mean to get the thread too far off topic... but ultimately if you don't need a power box for a 5 servo setup, the next question is surely when do you need one.


I don't know for sure (please correct me if I am wrong) but I would think if you used 2 receivers and a properly designed NiMH setup with high-end cells that had a nice low ohm rating that you would be able to build a system that was less money and was more redundant than a power expander setup?

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

It also eliminates a lot of points of failures such as match boxes, regulators etc. The Emcotec Unit that DA sells also does voltage regulation, has built in radio suppression filters to eliminate the need for servo chokes etc. Yes they are marketed well and used for good reason, most of the pros use them, such as Chip Hyde and several others. Do you need them in a 5 servo setup, not likley, however I run my 34% Extra with one on 2- 7.4 volt 4800 mah Lith Ion batteries and have never had an issue. Run 9 Jr 8611A servos throughout and have never had an issue. would I use one again, yes, makes for very neat wiring and a very stable voltage distribution system. If you dont want to use one then don't, but dont bad mouth them unless you have tried one!

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Thanks to everybaody!
I think i try one so i can use two lippo and have a battery switch.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

you can use 2 LiIon with 2 switch into 1 Rx no problem....

I fly a 40%er and mine is 2 batts, 2 regs into 2 Rx's and thats it.....

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

One thought you must keep in mind, the neat little connectors used are only rated at 3 amps.

Servo current draw when stalled can approach or exceed 3 amps, and draw in excess of 1 amp during normal flight loads.

5 servos x 3 amps ea = 15 and 5x1=5

Both values are well above the rating of the single connector power into the reciever. This results in added voltage drop across the terminal connection and degraded servo performance. You paid a lot of money for top of the line servos, go the extra mile to get the performance.

22 AWG wire is marginal in my opinion for these large servos, MIL Spec is 18 AWG for 7 amps
and this gets warm to the touch in sustained operation. Under sizes wire/connections results in oversized servos to make up for electrical losses when using standard componets

I would love to see the connectors that were fine for .40 sized models brought into the 21 century where 25 to 50% models are pretty common.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Well like I said I dont use matchboxes and regs.. or chokes for that matter. I did use a SmartFLy eq for awhile once until it broke in flight. From that point on I started to look at things and research things. I decided why add an unneccessay point of failure when you can spend a couple hrs working on linkage and your radio to achieve the same outcome as a matchbox or equalizer.

I hate to tell you but the "Pros" use them because they usually get them for free or little cost. That is all part of the marketing... they are also flying some of the biggest planes out there and push their planes to the limits.

"If you dont want to use one then don't, but dont bad mouth them unless you have tried one!" I am not bad mouthing them.. I am simply stating my opinion... this is a forum and that's it's purpose :eek:

If you read my previous post you will see I asked a question about a dual receiver setup vs. a power expander.



I am not sure this makes sense to me.... If this were true then you wouldn't be able fly any decent sized plane (80" and larger) hard?

The reason I say this is because your battery is plugged into 1 of those channels on your reciever. So if a single connector can only handle 3 amps then the first hard flight with 5 servos could draw between 10-15 amps... where is the extra 7-12 amps coming from?

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Four 33% birds and one 35%er. No powerbox,regulators,matchbox and no problems at all. Waste of money.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Intresting diskussion!
Does anybody know where to find servocables that dont have voltage drop?
One thing i have found is that with two batteries in the powerbox they only most take the half of the Amp.
The powerbox that i am intrested of is:

http://www.modellbau-deutsch.com/e/p...tion/start.php

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Wire size is generally not the culprit associated with electrical losses for our needs; 22awg is more than adequate IMO. Wire/connector quality, miss-matched connectors and connector count are the primary area of interest.

I use the exact length servo extension; this allows me to use minimum connector counts with a dedicated run to the servo interface for each and every servo.

Airwild Hobbies offers good HD stuff as do other OEM’s such as JR, Hitec and likely Futaba too. I have often used companies such as Radical RC and EMS Jomar Systems to provide custom length extension and wyes in the past with great success.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

I run 5 x 5955's and 1 x 5925 for my throttle through my 149DP receiver. 50 flights on my AeroWorks 50cc Yak 54 QB. I use 2,400mah TBM Lion's with single, fail-safe, voltage regulating switch.


Doug

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

I run 5 8611's with no problems

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Sounds like you're using a single 2400mAh battery and a fail-safe regulator? If this is the case your power supply is marginal IMO. A 7.4V 2400mAh Lithium-Ion is capable of delivering about 4.8 Amps sustained and momentary peaks to 10 Amps I suspect. The problem here is Lithium falls flat on its face if subjected to sustained high current demands. Your servo load has the potential to demand about 17 Amps during rigorous flight envelopes and or in a stalled condition for verrry short durations. If this load was to present itself severe voltage degradation is likely and you'd be in a world of hurt, especially with Hitec Programmable digitals. These servos require a minimum of 3.6V or so to remain booted up and operating. As I noted lithium batteries voltage decays at an alarming rate when exposed to high demand current loads.

A larger lithium battery (4800mAh) would be a wise investment IMO or a good old reliable 2400mAh 6.0V NiCad or even a low impedance NiMH battery will do the trick too.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Im confused, if the 3-pin connectors are marginal for one servo, how am i running half my 35% plane off one (from the battery)?

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

That's what I tried to point out earlier :)

The thing is if you take 2 low imdenacee NiMh packs they can handle up to 40 amps and only weigh 6 oz. more than a lipo / power expander setup.. with a lot less points of failure.

This is why I dont see the point of a power expander.... it looks like one central point of failure to me with a lot of unneccessary things added, all to make things look neat :)

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

The loads imposed are momentary with and averaged current draw near 2 amps for your model. However as heat builds from current so does the resistance and current draw. As noted previously the current spikes are momentary too. A 14 servo 40% model will spike at 24Amps or so doing aerobatic maneuvers…

The OEM connectors are like bottlenecks or maybe a funnel; servos will consume what’s available to them, more power better performance end of story…

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

The points of failure are identical, switches and connectors... If the switch fails on a servo interface who cares, if a power connector/lead fails who cares the model still operates without issue. If an onboard regulator/diode/switch goes south a redundant unit takes up the slack or its shut down and isolated from the latter power routing source.

Servo Interfaces send both batteries to the servo buss with short circuit protected power routing with failsafe ON operation for both battery packs and heavy duty high current plugs together with multiple servo ports which minimizes connector counts, wyes and the like… This is not plausible with your set-up without more goodies or not at all…

Furthermore some of these devices have redundant power routing, switching and provide head-room in the event of an EMI/RFI intrusion, individual servo failures are isolated from the rest of the system, servo signals are amplified and decoupled from the flight system its all good IMO… I’d worry more about a switch or connector failing, a battery and or wiring short taking out the power system or even a battery failure long before a servo interface failure, but that’s me.

According to the manufacturer of one the major players in Servo Interfaces a single documented failure has yet to be realized., go figure five years later and like the Eveready bunny there still going strong.

On the other hand I understand your apprehension too. These devices are certainly more sophisticated than a simple switch(es) and multiple connectors.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Don't drink the powerbox kool aid.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

According to Futaba Rep, the general rule is 1 servo per channel. 9 channel reciever = 9 servos(including high torque servos) I asked this question at the Toledo show a couple years ago.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Well it's def. an interesting debate to say the least. I guess there are valid points on both sides.

I can think of 3 40% Cardens that are run through extreme 3D constantly without so much as a matchbox which is why I don't see the need for a power expander. I will say they do have 2 receivers though.

Thanks for sharing some of the more detailed knowledge

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Mike described it better than I could, the best analogy I can come up with is a conventional light bulb. The bulb filament will conduct a large amount of current but the voltage drop across it results in energy being dissipated in the filament. In the light bulb this is the desired result, the heat generated produces light via the white hot filament.

In a car,boat, or airplane the wiring and termination are just to route the electricity to the device that is going to make use of the energy. In a model aircraft those devices are servos.

You or at least I do not want to waste the energy in heat generated in the termination or due to conductor loss. Ohms law says current (amps) X current x resistance = watts dissipated

The total resistance in a circuit includes internal battery resistance, termination to the battery, wire from the battery to the terminal, terminal to wire to switch, the switch, the wire to the receiver, the terminal to the receiver, internal in the receiver, the termination from the receiver to the servo wire, wire to the servo, and any terminations between, and do not forget the path all of the way back to the battery.

Every wire, every termination every junction has a definable resistance and current carrying rating.

Every place in the circuit where a voltage drop occurs, and it does occur even during a momentary current spike, the Ohms law equation does not have a time element, robs the servo from energy to perform its job.

Terminal and wire ratings are !QUOT!never exceed!QUOT! values for 100% duty cycles at a given ambient temperatures. Above this you risk thermal runaway and light bulb filament creation.

Now as Mike said the peak current values are momentary and are in fractions of seconds,
thusly no observable physical results of circuit overloading are apparent.

To those of you that are flying your aircraft on a single receiver, essentially pulling 6, 8, or 10
servos through a single 22 gage wire and 3 amp pin .... I hope you continue to have good luck, I simply cannot afford that kind of a gamble

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

There must be a lot of good luck going around!

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Yes there is a lot of luck, however I keep reading about unexplained servo failures that work perfectly after the accident, intermittent reciever failures, just luck I guess.

Luck, the bring together of preparation (or lack there of) and opportunity.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Actually, having disassembled a PowerBox SC-12 and traced things a bit, I can tell you that it is laced with potential single points of failure. There is no redundancy at all in any of the signal paths between the receiver and the servos outputs. Also, in the one spot where there is a measure of redundancy, i.e. a pair of linear regulators, one per battery input, they appear to have compromised that by introducing yet another single point of failure in the form a 47CTQ020S by International Rectifier. That part is a single D2PAK (single epoxy case) housing a pair of Schottky diodes that are internally connected as a common cathode pair. Each diode leg is rated at 20A max forward current.

If for some reason, one of the two diodes in that single package fails, then the full load being drawn will have to travel through the remaining leg. Because of that, it is possible that a failure of that type would result in higher heating of the junction that is still functioning. That extra heating may also contribute to a failure of the only remaining path for power to the servos. It is not a true redundant design. Perhaps there are some PowerBox models that are designed differently that don't have these shortcomings? I've only had the chance to peak at the SC-12 so far.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Yes, there are different models and manufacturers of servo interfaces, i.e., ModelBau PowerBox, Emcotec DPSI and Smartfly each has its own merits and limitations IMO...

And yes while the power routing from a single power/battery is not truly redundant with the SC-12, if one route fails the model fly’s home with halve the battery power. Even at 20 Amps the system is more than capable as a typical 40% model with fourteen 5945/8411’s consumes an average current of 3.6A performing aerobatic maneuvers. Emcotec’s approach differs considerably, specifically with power routing and the dual diode housing as noted above and then some.

I don’t think any of the manufacturers suggest they have redundant signal paths to the servos, I'll have to dig in to that one...

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Mike, are you suggesting two receivers, or an Emcotec/smartfly power expander in the 35-40% stuff. I can not find anywhere in the in the U.S. can you even buy an Emcotec DSPI. One of the Duralite Powerboxes has similar capability to the Emcotec but double the cost. Two PCM receivers are about the same cost as an Emcotec/Smartfly.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

All of this brings me back to a question I asked on page one...

If you used 2 receivers and a properly designed NiMH setup with high-end cells that had a nice low ohm rating would you not be able to build a system that was less money and was more redundant than a power expander setup? IE: 2 switches, 2 recievers, 2 NiMH packs.

I direct you to a battery setup like.. http://www.hangtimes.com/weightcompare.html

I mean you keep seeing people who say the battery channel on a reciever can only handle 3 amps. Yet you are constantly told to buy NiMH packs with the lowest resistance so they can put out the power when needed. You are also told to use the best quality wire with atleast 22awg or better and ultimately if we are well aware that a digital servo can draw 3-5 amps does it seem remotely logical that everyone designs receivers that only handle 3 amps per channel?

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Mike, I think you may have missed the point. The Powerbox SC-12 has a design that uses a common component to route the output of both regulators into one common point. If that one component fails in a way that takes out both paths, then the game is over. It's not a redundant design.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

The US Distributor for Emcotec is Desert Aircraft...

I use a single RX in my models with the Emcotec Mini/Duralite-PowerBox 40/16 for 35% models and the Emcotec DPSI-RV LDO/Duralite-PowerBox 40/16 or 40/24 for the 40% models. I have also used the dual RX set-ups too; and there is the DPSI Twin interface as well specifically designed for two RX’s one is used as a primary and the second comes online as a back-up RX when the primary fails, is locked out or activated from the TX.

When you add the total cost up for a second PCM RX and two fail-safe ON switched regulators the cost for a servo interface is not that hard to pass up considering you have eliminated several ancillary devices together with there associated connectors, electrical losses and shortcomings comparatively and NO you don’t really need these gadgets several goodies will fill the void without the added benefits of servo interfaces thereof.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

I understand that there is a remote possibility of some unknown failure mode of the dual diodes housed in single enclosure utilized by ModelBau could possibly render the system inoperative BUT, this is a distinct and remote consideration although it’s plausible nerveless. Power is supplied to the entire flight system in the event of a single power route failure, thus the REDUNDANT claim I believe. Remember the power routes are short circuit protected and each diode operates independently of the latter common cathode or not. FWIW, not all interfaces use the dual diode housing…

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

That's what I was interested in, which are models that are designed without that limitation. BTW, for a truly robust and redundant regulated power system , you need to use the right linear regulator chip. There are some really superior regulator chips available that eliminate the need for added parts such as isolation diodes on the output. Frankly, I was really surprised to see that part in there. Made me do a double take. Any time you have to add a part to overcome the shortcomings in a design, you're getting less than you bargained for.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

All Emcotec Servo interfaces use two single housed Schotkky Rectifiers for each power route coupling the power prior to the linear regulators...

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

And that makes perfect sense to do. I know exactly why they would do that.