rxAxilleas

hi all,
i am building a dauntless sbd and i need some help for the electronics setup.
how can i secure the plane from electronic failure? do i have to use any isolators? two rx? two bats?
i am thinking of using two bats , two rx and two switches and drive the aileron , and throtle servos with one rx and the elevators and rudder , flaps with the other.
is it right?

one other question i have is for the wiring setup.
for example , there are three servos for flaps , two for elevators , two ailerons...
i have soldered the wires for the servos together so to have one connnector to go to receiver. is it right or do i need an electronic gadget for that? is there any chance to have any interference ? if one servo fails , what happens with the others ? will they still work with this setup?
thanks and any help will be apreciated
achilles

rc4flying

My Feedback: (21)

Well, you never mention what radio and how many channels you will be using or size of the plane but, what you want and what you are doing with the soldering of the servo wires together will only be the start of a big head ache, in my opinion.
You may want to be looking into a PowerBox "Champion RRS" Unit. There are other choices also. These will allow you to do what you are after and give you some redundancy to boot. Soldering the servo together to plug into one channel is not what you want to do. It will take your servo voltage and have all three servos dividing up the 6 or so volts you will be supplying from that channel. With a PowerBox unit I describe will let you plug each servo into one channel separetly and supply each with it's own steady 6 volts. These units will regulate your power supply provide circuit protection and offer 3 or 5 channels of matching capabilities. SOme other capibilities allow for 2 rcvrs to plug into this unit and provide for switcing in the event of a rcvr failure. And it uses 2 batteries for battery redundancy.
In my opinion, If this is a large scale model, you ought to be looking into one of these.

Edwin

My Feedback: (2)

You have all the current going through that one connector. I wouldnt do that. In my opinion, a power expander would be the best way to go. I would isolate the power between your receiver and servos, meaning your receiver would be powered by a separate battery than your servos. I am using a home made power expander with 4.8v for the receiver and 6v for the servos. Then you can run individual lines to each servo which means you have a good solid ground and power supplied to each servo. Theres a bunch of gizmos on the market for expanding one channel to multiple servos. Just remember, the more complicated you make it the more fail points there are. Using good quality equipment and ground testing thoroughly is probably your best insurance.
Edwin

BuschBarber

My Feedback: (2)

Both JR and Futaba have devices that allow you to Match multiple servos on one control surface so that they are not fightinig one another. JR has the Matchbox. You connect the Matchbox to the Flap channel, for example, and connect all three Flap servos to the Matchbox. You use dials on the Matchbox to set servo direction, endpoints, speed, neutral, etc. When you deploy the Flaps, the servos will move appropriately. It is probably More important if you have say 3 or 4 servos on one Rudder, or 2 or 3 servos on one Aileron, as all the servos are on one solid control surface.

Power Expanders come in many sizes and can include features such as Matchbox functionality, Voltage regulation to each channel, Battery Redundancy, etc.. You need to look at Price, Weight, Features, and pick the model that meets that criteria. Another thing an Isolator or Power Expander can do is separate the batteries for the servos from the batteries for the receivers. Typically, you would have one small capacity Rx battery and two large capacity servo batteries.

Some people like multiple Receivers, for Redundancy. Using two 72Mhz receivers, for example, you have two long antennas that need to be routed separately. You can actually end up with reduced range in some cases. If you go with 2.4Ghz, it is much easier. Some people used to put half the servos, for a given control surface, on one receiver and half on the other. If one receiver failed, you could still control the plane. If you use a Power Expander, it may be a little more difficult to use two receivers in that way.

victorzamora

Only sure fire way to do it I know of is pretty cheap. It also works 101% of the time. I'll guarantee it. NEVER will you have any electrical problems if you install one of these on your plane: http://www3.towerhobbies.com/cgi-bin...?&I=LXFU23&P=M



Lol, you thought I was serious .

rxAxilleas

hi guys,
thank you all for all the help and info you provided.

i use jr 378 tx and jr646 pcm receiver i think it is 8 channel.
the channels i use is:
-throtle
-aileron
-elev
-rudder
-gear
-flap
-brake

one important think is that every surface has one servo. so there is no issue of any servo fighting each other.
one the wing there are:
2 ailerons,2 brakes, 3 flaps, 1 gear air valve
i glue the wires of the ailerons -flaps-brakes together because i wanted to lead all the wires to a harness and a 9pin computer connector , so to connect and disconnect the wing easy.if it is a problem i can use a connector with more pins and i can attach a servo gadget as you describe.

so if i route every servo lead at the fuse seperately, then i could use two rx-bat .
i am thinking of :
1st rx and bat : aileron1,elevator1,ruder,throtle, flap1,brake1
2nd rx and bat : aileron2,elev2,flap2,flap3,brake2,gear

of coarse if i use champion rrs system as Joe suggests i would be much better but do i still need an expander or isolator(is this the same thing?) to separate the bats fro servos?do these two gadgets are enouth?do i need something else?
do the two rx system have any problems with the antenas that will be side by side?

i am not familiar with that kind of equipment and terminology and i am not sure what exactly i need.
can someone suggest what a complete system needs for the above plane?

many thanks!
achilles

BuschBarber

My Feedback: (2)

I have never used two receivers as I have never had a receiver fail. I know that it can happen. As I mentioned before, using two Non 2.4 receivers can shorten your total range. Just a consideration and does not mean that it won't work.

A simple, relatively cheap device is the I4C Isolator. You can hook up one Rx battery and two Servo batteries. The servos plug into the Isolator and the Isolator plugs in to the Rx. I have used that device and I hook up a Switch Harness to each battery so I can charge them separately.

JR/Spektrum makes a 2.4 Rx that has heavy duty wiring, with Deans Ultra connectors, for Two battery packs. It is designed for Higher Current Draw situations.

rxAxilleas

HI,
where can i find this 14c isolator you mension?can i put multiple servos for the same channel on it?if not, how can i do that?
many thanks
achilles

BuschBarber

My Feedback: (2)

Check out http://www.rcuniverse.com/forum/m_1237707/tm.htm

The Isolator allows you to connect one servo connection to each channel connector on the Isolator. The Isolator has pigtails for each channel and they each connect to a channel on the Receiver.

The JR Matchbox, or the Futaba equivalent, allows you to connect up to 4 servos to one channel. Dials, on the Matchbox, allow you to Reverse servo direction, for each individual servo, and set Neutrals.

Applications would be servos on each Elevator half, multiple servos on one Rudder, multiple servos on each Aileron or even one servo per Aileron, or a servo on each Flap. If you had multiple servos on each Aileron, for example, you could use a Matchbox on each Aileron half.

PlaneHeli

I am not sure whether you are referring to airbrakes or wheel brakes. But It may be better to have either both brakes on together or no brakes at all.

If you have the wheel brakes on a separate Rx/Battery, if one fails you may have only one brake activate causing a rapid groundloop on brake activation during landing.

If you are referring to airbrakes, you may get severe yaw if activated while airborne.

Just a thought.

dirtybird

My Feedback: (5)

As you can see there are a lot of gagets you can buy if you need peace of mind.
Let me say this: I have flown digital proportional systems since the late 60's all the way up to 100cc gas.
I have never used any of those gagets and I have never had an electronic in flight failure.
I have always used just one battery, one switch, and one receiver.
I have had switches servos and batteries go bad but I always found them on ground checkout.
I guess I must be just very lucky. But if that is true why can't I win at poker?

BuschBarber

My Feedback: (2)

You can use a Y harness, on any port of the Rx, and add a second battery. It eliminates all the gadgets and gives you redundancy on the battery.

When you get into Giant Scale, Turbine powered Jets, and other aircraft where the value is several thousands of dollars, it is worthwhile lookiing at some of these devices. If you are running 10 servos or more, off one Rx and one Rx battery, you need to look at how much current the system is drawing and how to ensure that you can deliver the power. At the same time, if you are using multiple servos on each control surface, you need to either use Programmable servos or a device to make sure the servos are in sync.

Redundancy, Power Distribution, and Servo Balancing can be handled with a PowerBox, for example. It is not unreasonable to go in that direction.

dirtybird

My Feedback: (5)

I don't fly airplanes that cost several thousand dollars and I don't think the thread starter is quite there yet either.
BTW an A123 battery will handle up to 60 amps and maintain the voltage at more than 5V without a regulator.

BuschBarber

My Feedback: (2)

I have been flying RC since 1978 and control line since 1956. As you progress in the hobby, you learn to improve upon the way you do things. You take extra steps to reinforce an ARF design. You throw out the cheap hardware and use better hardware. You get better chargers and pay more attention to maintaining your batteries. You use better servos and slop free linkages.

I do not necessarily use redundant batteries on every plane I fly, nor do I use Power Boxes or multiple receivers. They have their place. If you check your equipment often and cycle your batteries once a month or whenever they seem to be loosing capacity, you can save an airplane. I always check my battery voltage before every flight. I go over all the linkages once a day or after a hard landing. I have a good Tachometer and a good Digital ESV.

I switched to 2.4 and away went RF noise, errant shootdowns and waiting for the frequency pin.

I have had very few equipment problems.

Definately don't go out and spend a ton of money on all the high priced gadgets. Just get what makes sense at the time and be aware of what is available should the need arise.

rxAxilleas

hi guys,
all of you are right and the subgect is a very long to discuss . also the plane isn t so big to justify any expensive gadget.
i think that two bats and one receiver will be ok.
the only concern i have is the three flaps with the three servos.as i say each one have each own servo so i dont need servo machbox.
is it ok if i use two y harnesses or solder the wires together?
the servos are hitec 475 i think about 61oz at 4.8v. the curent draw is not very high but is there any signal loss from the receiver as the signal divided to the three servos?the wire length is about 25" max. the powerbox system states that there are amplifiers in it. is it necesary for the above setup?the brakes are airbrakes and i think i will never use them. the ailerons are futaba 3050 digitals with a y harness and the elevators the same.

also i am thinking to go at 6.0v . is it ok? rx Jr649 pcm do i need any regulator?

thanks again for the help.
achilles

Josey Wales

My Feedback: (61)

Good information BuschBarber and I agree 100%.

JohnBuckner

My Feedback: (1)

I have used both four and six HS 225's all on a custom harness to a single Rx port for throttles on both four and six engined airplanes with no issues. On the six the furthest servos from the Rx are about forty inchs.

Is this SBD the original Skyshark sixty size kit or something about that size. If so I see no issues runing three standards (HS-475) on separate surfaces with a three way link.

John

BuschBarber

My Feedback: (2)

Some people use a voltage regulator, with 6v packs, just to keep the voltage down to 6v as the fully charged pack could top out at 6.8v. I have only used a voltage regulator if my servos will not work at 6v. My JR791 retract servos will not work properly at 6v. If I am using LiPo batteries, I use a 6v regulator.

You have to see how your system behaves at 6v.

rxAxilleas

hi John,
the sbd is 85" from J. Bates plans.i made already a custom harness that has an 9pin computer connector on the midle so to connect and disconnect only one connector instead of 4 (1ailerons,2airbrakes,3flaps,4gear). Joe and Edwin suggested that this setup is dangerus and i am a litle afraid .althout the servos are not attached on the same surface.is there a chance to have signal loss ?the worst case is the flaps that has three servos. the other surfases has only two (ailerons, elev, brakes) and i think that i am not the only one that uses a y harnes to drive two servos.i am thinking if the three servos at flaps make a truble to the receiver somehow . i used heavy duty cable for the harness i made. but the cable i not twisted.see i am new and learning...
thanks
achilles

dirtybird

My Feedback: (5)

If you are going to drive more than two servos from one receiver output maybe its time to employ one of those gadgets. Each time you ad a servo to an output you increase the load to that output and you run the risk of the servos not responding. They may work OK on a check but fail later. One of those servo synchronizers sold by the manufactures should provide the necessary amplification and give you the ability to synchronize the servos.
Remember when you make your own wireing harness you must be very carefull and carefully check it out. The wireing you buy is made by skilled technicians that have lots of experience making the same things over and over. They know what might go wrong and avoid those things. You are going to have to learn those things as you go.

JohnBuckner

My Feedback: (1)

That airplane is larger than suspected and a much higher servo count. A good candidate for isolating the rx with its own battery in that way you could still use the three flaps on a Y. I beleve there are devices for doing just that but that is not something I have done and will defer to those who have.

John

onewasp

21 Posts since this question was posed __ "how can I secure the plane from electronic failure?"

The VERY simple answer is/was that you do NOT.

The only thing that can be done is to lessen the odds of failure.
Quite frankly one of the BEST ways to bring the odds to your favor is to avoid complicated set ups.

In fact, the originator of this thread, given his desire, is his own worst enemy!

The ONLY fail safe which works is to leave the airplane on the ground!!
Then of course you have to hope no one steps on it.

slarty

Aah... but then it wouldn't be "electronics" failure !!

onewasp

True!!!
But then imagining that it were my airplane_______!!

Did you ever notice how a soup bowl 'breaks' but electronics "fail" ??

Now, if we had an electronic soup bowl________

slarty

Hmmmmm...... the electronics I play with (now) Spark !! BIG TIME !! But they don't let the magic smoke out oddly enough... [sm=confused.gif]

Hand held transmitters do though...... how verily odd !!