steveline9

Hi all, I am building a S/M Hawk at the moment and dont know whether to fit an opto-isolator or not.
I am running 6 digital servos and am worried about two things as follows:

1 Length of servo leads (2m on ailerons and elevators).

2 Current through the reciever

I like to keep things simple so ideally would like to know if i can just use the reciever with this setup rather than complicate things with more units

schroedm

My Feedback: (1)

With 6 servos I'd say you need not worry about either of your concerns.

Out of interest, do you really need a 2m extension lead for each aileron servo?? I have never needed a lead that long on any of my giant scale gas models with 9-10ft wingspans??

Rgds,
Mark

Erik R

My Feedback: (32)

Steve,
I lost a bandit last year because the ecu sensed a voltage drop in the receiver as a loss of signal/pcm lockout when I blew flaps to set up for landing.That plane didn't have an isolator.I have a cyclone I bought turnkey that has an isolator installed because the same problem occurred.Simjet in the bandit,AMT in the cyclone.Just maidened my super bandit successfully with the isolator.Using the ED 111 in both.Bottom line if you install one,you'll never know if you really need it.If you don't,you'll find out the hard way like me.No brainer.Spend the money,and have peace of mind.Good luck,
Erik

schroedm

My Feedback: (1)

I don't really know the technicalities behind this but that sounds a little worrying? Is this "drop in the receiver" normal? Isn't fitting the isolator potentially just "sticking a band aid" over what could be a bigger problem????

mikuk

Hi,
Fit one for peace of mind, all my turbine models have them fitted, dual battery /switch on the servo side (SM Services 8ch opto) just the least used servo to the rx, would love to source 10channel opto, anyone know of one?? Mike

George

My Feedback: (57)

Erik, I had the same exact thing happen to me TWICE a few weeks ago before I figured out what the problem was. Fortunately, I did not lose the BobCat on either incident, just a few scratches and a couple cracks. My problem was a "brown out" due to a degraded battery pack that was being pulled down too far when ever I exercised too many servos at one time and it would shut the turbine down. I had many flights before that occurred and it when it started, it would happen during the second flight on the charged battery. The battery has been replaced and all is well now.

I'm unfamiliar with the isolators and have no experience with them. I would like to learn more, but am hesitant because it is just one more component to worry about.

George

Spartan Missile

So 8 digital servos in a large jet into a Rx is not a good idea ?
It's a shame that the Rx manufacturers do not post any data about this.

lov2flyrc

My Feedback: (24)

Try running an Eagle Tree Telemetry system and watch your onboard voltage during high G manuvers or flap deployment at speed, make you think twice about not having some sort of circuitry that can handle these amp loads. Typically not an issue on the smaller airframes but gets a bit scary when you have many large digitals all under load at the same time. Never really thought it was an issue till I used the eagle tree and had the ability to monitor onboard voltage during flight [X(]
Necessary on the Hawk, probably not.... But, cant hurt

Flyjets

My Feedback: (51)

Hi

I have personal experience with these devices.

Stay as far away from them as possible I lost a large acrobatic plane due to the failure of this unnecessary piece.

On Jet Models for the most part the servo draw doesn't warrant the use of these type of devices. Once you get into multiple servos ganged together or large control throws these devices are needed.

Best of Luck
Ian

lov2flyrc

My Feedback: (24)

Ian,
Care to eloborate on which device and failure??
Todd

reo

My Feedback: (130)

The IMAC fellows flying the big gas stuff have been using isolators for quite some time with lots of success.

The benefits of an optical isolator like the EDR-111 are two ot three fold:

1).....they allow a separate power source for the servos only. This is a plus because when using multiple digital servos with long leads and large surfaces current to the servos becomes a real issue. Regardless of the amount of amps fed into the RX, the receiver is still limited to the the amount of current it can provide to the servos and at times it will not be enough.

2).....eliminates RF issues with long leads, etc.

3).....amplifies the control signal to the servos.

IMHO, there is no downside to using a device like the EDR-111, in short, cheap insurance.

Ron

Flyjets

My Feedback: (51)

Todd

I lost a Dave Patrick Edge when the Jomar Optical Isolator failed.

Batteries where Lith- Ion Fromco along with Kurts regulators feeding the receiver and the Jomar Isolator.

The Jomar Isolator glitched the signals to the Futuba 5014 G3 receiver.

Even though Fail Safes were set the plane never entered Fail Safe because the Jomar controlled all servos output.

After the crash I was very upset Model never made it above 5 feet on Take Off. This was a machine that was flown in competition several times and had 30+ flights on her.

My Team Futuba buddies wanting to see if the G3 5014 was the source of the problem removed each component. The servos were still glitching but when the Jomar was removed all was fine.

The Optical Isolator was sent back to them and they did send me a new one. Needless to say I now run a very different setup on my machines. Here is a photo.

Ian

Spartan Missile

FYI, from the Macgregor site, the UK distributors for JR

http://www.macgregor.co.uk/faq/General/optoisolator.htm

Dave Wilshere

Guys

I run 8 digitals, one standard and two electronic valves through a JR 1000DS Rx with a std JR PM 10 switch and JR 1900J battery.

268 flights tell me its safe-28 flights in one day (with charges) tell me its safe.

I still think that PowerBox systems are a good idea for back up, but all my standard size jets including my SuperBandit use a standard JR set up with out a problem...its the quality of battery and switch that makes the difference...

Dave Wilshere

JohnMac

Personally I have seen Opto Isolators solve problems and also create them. In my opinion you should only fit one if you need one.
The question of redundancy is a different matter. Statistically, batteries are the item most likely to spontaneously fail, followed by the switch. I have had a few such incidents up to the point I decided to fit twin batteries into everything I possibly could, and none since. I have still had batteries fail, but the second battery has saved the day.
Dave, correct me if I am wrong (because I don't have one) but does the power box use 2 batteries for the servos and a third one for the Rx?
Regards,

John

Dave Wilshere

john

No, two batteries supply the Rx and servos-but each channel 5 on the expert and 7 on the Pro, Competition and Champion all have their own supply and amplifier.
The 5 or 7 leads plugged into the Rx all supply power to the Rx.

Dave

JohnMac

Hi Dave,
OK thanks for the clarification.
Regards,

John

Gazzer

I was intrigued by MacGregors view on this and where the ABCW technology fitted in.

I truly wonder what effect cable screening would have, given that most sophisticated cabling technologies have screening, is it about time, is there a need and justification to move from the current servo cabling to those that are fully screened?

I'm not an RF expert at all but it seems that longer cables are most at risk, so screening them would provide a value of proportianate benefit.

love to hear views and then of course, how do we get a manufacturer/supplier to start providing screened cables if this would improve things??

Gazzer

Speedbird66

Hi All
I have been following this thread and would like to make some comments:

Yes, screening of the servo cables would probably be good. However, if you are using long servo cables you would still benefit from some kind of signal amplification. The PowerBox system does that and a few other things as well:

- Signal conditioning and amplification (to servos) which also is an active protection to glitches induced by signals being picked up by the long servo signal leads
- Individual short circuit protected power supply to servos (with voltage regulator in some models) which means that you will get the specified torque of your servos.
- Separated power supply of reciever (with voltage regulator in some models) independent of the servo load
- Dual battery power management (short circuit protected)

My personal opinion is that there is a potential risk for voltage drop in the reciever due to heavy load by digital servos being plugged directly in to the reciever. When this happens the reciever will either die or go in to fail safe.

I also think that the PowerBox system is well spent money for any Jet Model and is among the safest installation available on the market today (dual reciever system excepted)

/Johan

sirrom

My Feedback: (4)

I read alot of stuff on the internet and take most of it with a grain of salt, but I read this thread and thought that I should chime in. I am not an expert on batteries by any means but Red Schofield is. He talks about this problem on his website the battery clinic. Click the link below and it will take you to his article. No offense to anyone here but I am more inclined to believe his words since he has forgotten more about batteries than most of us will ever learn. I will however say for extreme servo wire lenghts there needs to be some protection there and I tend to take my ques from the giant scale flyers who's airplanes see more voltage through their systems. Yes some of the biggest jets like the BVM F100 with all it's servos see quite a bit of votage but not as much as a 40%+ aerobat with 3 to 4 digitals per wing, 2 or 3 digitals per elevator and 4 digitals on a rudder. Thats 14 to 18 servos in one plane all pulling serious amps. I wonder what the amp draw is on a giant scale aerobat when doing a high deflection manuever like a lumshavak, or just a plain and simple snap roll deflecting all surfaces at the same time.

http://www.rcbatteryclinic.com/parallel.html


Patrick

Speedbird66

Patric
That is a very good article. The was a similar article posted in the RC JET Int Magazine by Tom Wilkinson a year ago as well. As for the the dual battery power function of the PowerBox system I see this an nice feature that comes with package. There is no harm with the diods - they are just there in case of a short circuit.
The important functions of the PowerBox are the signal amplification and individual power supply of servos and reciever.
Also worth mentioning is the min voltage memory that will give you an indication of how the batteries are performing during a flight.

/Johan

sirrom

My Feedback: (4)

Johan,
I dont have a problem with the powerboxes because for giant scale airplanes they do have their place but for something like a Bobcat or similar I don't think it is needed. Guys are over complicating their electrical systems in small to medium jets when not needed and what are actually the chances of a battery pack shorting out? I have been flying since I was 18, and in 19+ years I have never had a pack short out on me.

Just my .02 worth

Patrick

Speedbird66

[quote]ORIGINAL: sirrom

Johan,
I dont have a problem with the powerboxes because for giant scale airplanes they do have their place but for something like a Bobcat or similar I don't think it is needed. Guys are over complicating their electrical systems in small to medium jets when not needed and what are actually the chances of a battery pack shorting out? I have been flying since I was 18, and in 19+ years I have never had a pack short out on me.

END QUOTE

Patric
You are spot on with your comments about the rare occasions of battery failures. Most pilots use sophisticated chargers to cycle their Rx batteries anyway just to be shure of the battery condition. Batteries tend to degrade very slowly and very seldom fail spontaniously.

To me it doesn't appear ideal to plug one battrey (ore two in parallell) in to the battery slot of the reciever and having a number of digital servos drawing a significant power through the thin copper foil of the circuit board of the reciever. For that reason only I believe a separate power supply of the servos is safer and better.
When a servo is jammed or by any other reson draws a high current the reciever may suffer from a voltage drop which could lead to shut down or going in to fail safe.
The PowerBox eliminates this failure mode completely. Even if you short circuit the power to one servo everything else will work.
There are also special power switches available (Graupner) that separates the power supply to the servos which is in my opinion the minimum requirement for safe operation.

/Johan

Erik R

My Feedback: (32)

Steve,
I had a 4000mah Duralite in the bandit.When I extended flaps at speed the voltage draw to the flap servos caused a voltage drop in the receiver.I never lost radio,but the ecu sensed the voltage drop as a radio failure,and commanded a shutdown of the turbine.An ECU commanded shutdown will not cause the white puff of smoke that an air bubble in the fuel line will.The bandit is so quiet that I was unaware the engine was shut.As I tried to add power nothing happened and the ensuing stall was unrecoverable.Cost me a 10K bandit.The original owner of my cyclone said the engine flamed out every time he blew flaps until he put an isolator in.I flew it all last summer with zero flameouts.I am not a fan of Jomar products,but have been using The EDR-111 in my jets and 33% airplanes with no faults or failures.I believe they cost $75.Cheap insurance for an expensive jet.Good luck,
Erik

martin.lees1

Advice needed.

I am now confused about my intended set up on my rookie .

9 Digital servos
3 std servos
1 jetronic valve

2 1700mah nicad,s Through S&M battery backer , with 2 heavyduty switch harness.
Rx Futaba 9ch


Will my reciever be able to take the load or will i need a power box ?.
The way i see it is that more components you add the more links you are adding into the chain.


Rgds Martin.