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Voltage drop and the dreaded "Brownout" , What's really at fault ?

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Voltage drop and the dreaded "Brownout" , What's really at fault ?

Old 09-23-2015, 12:08 PM
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init4fun
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Default Voltage drop and the dreaded "Brownout" , What's really at fault ?

Hi guys ,

As a continuation of the technical discussion portion of that trainwreck of a Spektrum thread , I offer this thread in replacement . Please use this thread to help expand folk's knowledge of RC control systems without the need to belittle or "one up" the next guy . We all know a fair bit about electronics , that kinda goes with the territory of RC , and several of us (RG Burrell , Myself , and a gent named John to name a few) are of the notion that the entire modern RC control system needs examination to determine exactly where the "soft spots" are , current carrying wise . Good Grief , ever actually cut into and see how precious little copper there is in a 22 or 24 gauge piece of wire ? And we're gonna power 5 digital servos from that ?

A chain is only as strong as it's weakest link . This statement works for not only actual metal chains , but electrical ones too .......
Old 09-23-2015, 02:16 PM
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dirtybird
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One thing you should keep in mind. There is a failure that is quite probable that has not been mentioned..
If a servo gets stalled it will draw very high current. If that draws the voltage down to where the receiver browns out, and the servo is a digital it will stay put continuing to draw extra current and will not allow the receiver to reboot. You will then seem to lose control.Always make sure there is no chance of servo stall especially on things such as motor control, flaps and landing gears.
And never use a digital on those controls.
Old 09-23-2015, 03:15 PM
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Checklst
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+1 on dirtybird..........he gets it.
Old 09-23-2015, 04:51 PM
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Well I think the MFG'ers are well aware of the power demands of the current technology... the older receivers are just that, older technology... things progress, new ideas come to fruition... just look at Futaba's R7018SB receiver, JR's / Spektrum's power safe receivers... they basically have a built in servo power buss with dual battery redundancy ready to accept the hv digital servos... I like the design of the R7018SB, but it would be nice if they would release a version with a separated power buss, as I like to put the receivers high up out of the way of the rest of the radio gear and don't particularly want 18 servo leads following up to the receiver, I rather have the buss remote were I can hide and dress in the leads in a neat and tidy fashion... any of the older receivers can be setup to be just as reliable using aftermarket power management systems... that's why SmartFly, PowerBox, and the rest developed these power boards, because there was and need as the demand increased for these larger more complexed models, with more and more servos added.... clearly the receivers were not going to handle the increased demand placed on them... that's the nice thing about innovations, its driven by the need to improve on the current technology.



John M,

Last edited by John_M_; 09-23-2015 at 07:01 PM. Reason: Fixed Boo Boos
Old 09-23-2015, 05:57 PM
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dirtybird
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The reed system I flew in 1960 had separate power supply for the receiver. What goes around------
Old 09-23-2015, 06:12 PM
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I suspect you need to start, by educating people in the fact that they even have an issue to begin with. The ignorance level among the Community is amazing. They won't even invest in a Voltwatch and bang the servos around to see if they have an issue; and if they do, they will ignore the results because plane flew fine before. Then we could give guidance on a good setup for the particular application. Crashing due to radio failure these days is really not acceptable given the quality of the equipment available.
Old 09-23-2015, 07:26 PM
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Yes, better written manuals would be nice instead of the bare basic information you get, most are so vague you have to figure out the rest on your own.

I don't have a volt-watch or any other voltage display permanently connected to the airborn system... but I do have the receiver and servo buss batteries on telemetry, so I can see the battery voltages from the transmitter... I also have a lead plugged into one of the spare servo buss inputs; that's where I can plug in my multimeter to take voltage readings from.


John M,
Old 09-23-2015, 08:19 PM
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Jump in the shower. Nice hot water. Then someone jumps in the bathroom shower off the adjoining bedroom, just on the other side of the wall, cranks up the hot water to max and... yours changes, typically not for the better. Only so much hot water is available and stored in the hot water heater. How about a third person in a third shower....Start running the dishwasher and clothes washer in addition to three showers and... and... and.... well, it just doesn't work out very well.

It's not any harder than that. There are solutions: two or three water heaters, lower flow shower heads, blah, blah, blah. But that's as hard as it gets.
Old 09-24-2015, 03:45 AM
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I have flown the giant scale stuff on JR and Spektrum equipment as much as anyone, I have yet to experience the dreaded brown out or loss of aircraft using this equipment. A typical setup for me like in one of my 50% + airplanes goes like this, 8 ea. Hitec 7990s on the flight controls and a JR DS 3421 on the throttle, or 13 ea. JR 89811s on the controls surfaces and a JR DS 3421 on the throttle. I have used the Smart Fly EQ6 Turbo power expanders to feed those monster servos and have also used a single powersafe receivers to feed them as well. I always use a pair of good quality 2500 to 4000 ma lipos for power in applications like this. When I am setting up small or large airplanes for first flight I insure there is absolutely no binding, or slop issues in the linkage from the point of servo outputs to control surface or throttle inputs, no range or bind issues between transmitter/receiver, I also insure a safe C/G that will allow me to fly, land, and make adjustments. You guys ever notice when you buy really high torque servos they come with cheap plastic servo arms? You don't use them in the really large stuff do you? Most guys I know, myself included toss them aside and replace them with something like SWB arms that are up to the job at hand. It kinda goes with everything else we place in our toy airplanes. There are installations and then again there are installations, just like there are builders and then there are builders... As I have stated before there is far more brain trouble in this hobby than equipment trouble, but that is just my own opinion, and you now what they say about opinions. Happy flying guys.

Bob
Old 09-24-2015, 04:51 AM
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Originally Posted by dirtybird View Post
...especially on things such as motor control, flaps and landing gears...never use a digital on those controls.
Interesting, never considered this, but makes great sense. Replacing the digital servos on planes where I have them in these applications might make for a good winter project.

Good advice!
Old 09-24-2015, 06:23 AM
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Originally Posted by dirtybird View Post
One thing you should keep in mind. There is a failure that is quite probable that has not been mentioned..
If a servo gets stalled it will draw very high current. If that draws the voltage down to where the receiver browns out, and the servo is a digital it will stay put continuing to draw extra current and will not allow the receiver to reboot. You will then seem to lose control.Always make sure there is no chance of servo stall especially on things such as motor control, flaps and landing gears.
And never use a digital on those controls.
Good info dirtybird but I always use digital servos on all my surfaces , use a hitec servo programmer with a amp and volt test , as I set up my throws I watch the current on every servo adjust them with end point so there is no bind or excess current draw , the good thing about digital is the output is constant and centering is never a problem and they are programmable and always back to same neutral position , and I also have on board realtime telementry which monitors my batteries and sends the info to my tx and my smart fly eq10 will not allow excess current draw it will shut down that servo thanks

Last edited by jmiles1941; 09-24-2015 at 06:27 AM.
Old 09-24-2015, 06:35 AM
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RCKen
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Ok, this is good guys. I like to see that this subject has reopened so that it can be discussed in a thread that can get the info out to members that might really need it without having to read through the 13 some odd pages of the previous pages of the previous thread. But please know this, if we see any of the junk that polluted the other thread on thread on this subject it will be removed from this thread without any hesitation or notifications. We want to make sure that our members our helped out by information such as this and not drawn into pointless mudslinging battles like the other thread turned into.

Init4fun, thanks for getting this back up and running.

Ken
Old 09-24-2015, 06:44 AM
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^^^^ Thanks, Ken!
Old 09-24-2015, 07:46 AM
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Let's start at the beginning. NICD and NIMH batteries do not cause crashes. If they did, we would not have been able to fly giant aircraft since 1953. For all you "newbies" out there. Please read the directions that come with the Battery Packs or go to a Reputable Dealer that publishes information for new Pilots.

a NIMH battery pack gets charged, taken to the field and flown, taken home and recharged...Etc, Etc ETC. I the old post people that really wanted helped kept saying " I flew it a dozen times and then the radio failed" NOT TRUE...You failed to read the directions...

QUOTE: " A NIMH battery must be fully discharged after each day of flying. WHY? because they will build up a memory of where you were when you started charging them. After a few times they will only let you charge the battery pack frm where you left off.

in other words, when you discharge it and then charge it you actually get a 99% charge. If you just continually charge it and not get a full discharge you may have a 99% charge but only for 30% of the battery. That means that instead of flying safely for say 9 minutes you will go dead after maybe 3 minutes and guess what...tou are below 3.5 volts or even 4.8v as Spektrum says they require.

A six v battery is a six Volt battery.

Go to REDMAN RC and read about batteries....I like those guys...They sell all the stuff I buy for my big planes . That was not what the first post was about.

Last edited by RCKen; 09-24-2015 at 08:52 AM.
Old 09-24-2015, 07:49 AM
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Originally Posted by TOPGUN WINNER View Post
Let's start at the beginning. NICD and NIMH batteries do not cause crashes. If they did, we would not have been able to fly giant aircraft since 1953. For all you "newbies" out there. Please read the directions that come with the Battery Packs or go to a Reputable Dealer that publishes information for new Pilots.

a NIMH battery pack gets charged, taken to the field and flown, taken home and recharged...Etc, Etc ETC. I the old post people that really wanted helped kept saying " I flew it a dozen times and then the radio failed" NOT TRUE...You failed to read the directions...

QUOTE: " A NIMH battery must be fully discharged after each day of flying. WHY? because they will build up a memory of where you were when you started charging them. After a few times they will only let you charge the battery pack frm where you left off.

in other words, when you discharge it and then charge it you actually get a 99% charge. If you just continually charge it and not get a full discharge you may have a 99% charge but only for 30% of the battery. That means that instead of flying safely for say 9 minutes you will go dead after maybe 3 minutes and guess what...tou are below 3.5 volts or even 4.8v as Spektrum says they require.

A six v battery is a six Volt battery.

Go to REDMAN RC and read about batteries....I like those guys...They sell all the stuff I buy for my big planes . That was not what the first post was about.
We all know how to add money and install all the trick stuff...Right Ken?

just a footnote: That is the main reason to go to A-123 (LIFE)
Old 09-24-2015, 08:31 AM
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Originally Posted by dirtybird View Post
The reed system I flew in 1960 had separate power supply for the receiver. What goes around------
Dick Branster built the first one in Birmingham Michigan...He put it in a Stearman and crashed into a hanger at Selfridge AFB while demonstrating it to the USAF. Seperate power supplies were used by everyone...Planes were big and the homebuilt radios were even bigger...lol
Old 09-24-2015, 08:53 AM
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In the beginning of digital proportional control, there were only what we now call analog servos. They were called digital then. In addition the receivers were made of discrete components. There was no microprocessor in there all the way up thru 72. Such receivers will work all the way down to 1 V with reduced range. They don't suddenly quit and reboot. I once flew several flights with a shorted cell in the battery pack. It was 3.6V when I got around to measure it. I hadn't noticed any difference.
The early digital radios all used NICDs. NICD's have a very low internal resistance. The early NIMH batteries had a much higher internal resistance but in most cases we didn't notice a difference because we were using discrete component receivers.
The problem arose when we started to go to 2.4. The microprocessor in there did not like NIMH. Newer NIMH's are much better. I still would never use one in the airplane NICD's are best and A123's are better. NIMH's are for the TX.
BTW Memory was attributed to NICD's not NIMH's I don't buy it for either one. The problem started when NICD's were initially charged with the constant voltage chargers used for liquid acid chargers. I have always used constant current chargers on mine
Old 09-24-2015, 08:59 AM
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Originally Posted by TOPGUN WINNER View Post
Dick Branster built the first one in Birmingham Michigan...He put it in a Stearman and crashed into a hanger at Selfridge AFB while demonstrating it to the USAF. Seperate power supplies were used by everyone...Planes were big and the homebuilt radios were even bigger...lol
I had an ED reed system built in England in 1955.
ED designed and built reed systems prior to WW2
Old 09-24-2015, 09:07 AM
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dirtybird
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Originally Posted by jmiles1941 View Post
Good info dirtybird but I always use digital servos on all my surfaces , use a hitec servo programmer with a amp and volt test , as I set up my throws I watch the current on every servo adjust them with end point so there is no bind or excess current draw , the good thing about digital is the output is constant and centering is never a problem and they are programmable and always back to same neutral position , and I also have on board realtime telementry which monitors my batteries and sends the info to my tx and my smart fly eq10 will not allow excess current draw it will shut down that servo thanks
There still is the possibility of getting something stuck in the servo path. Especially a landing gear
Old 09-24-2015, 09:56 AM
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Originally Posted by dirtybird View Post
There still is the possibility of getting something stuck in the servo path. Especially a landing gear

But with the smart fly eq10 if anyservo draws too much current it shuts down the signal to that servo so it wil not contuine to use higher current , now this is only if you have multiple servos on surfaces , like I have 2 on each wing , 2 on each elevator , and 2 on my rudder , 1 servo on each surface will move the surfaces enough to save the plane thanks for your response

Last edited by jmiles1941; 09-24-2015 at 10:02 AM.
Old 09-24-2015, 11:49 AM
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What a great thread, full of very useful info and without the degradation into whinges and belittling certain radio brands. Thanks, great points on digital servos pulling the voltage down.
Old 09-24-2015, 11:54 AM
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Originally Posted by ackroyd View Post
What a great thread, full of very useful info and without the degradation into whinges and belittling certain radio brands. Thanks, great points on digital servos pulling the voltage down.
ackroyd digital servos will always draw more , when you set up your planes use a servo programmer and a volt amp meter , that way you are sure your setup has not caused you and problems
Old 09-24-2015, 12:02 PM
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Originally Posted by ackroyd View Post
What a great thread, full of very useful info and without the degradation into whinges and belittling certain radio brands. Thanks, great points on digital servos pulling the voltage down.
here is how I setup all my servos for volts and amp draw
the only difference they are in the plane hooked up to their control surfaces
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Last edited by jmiles1941; 09-24-2015 at 12:06 PM.
Old 09-24-2015, 12:04 PM
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I must admit, I prefer high torque analogue servos, but then I'm only flying a mix of 40 size aerobatics and 1/4 WW1 fighters and a 1/4 Piper Cub.
Old 09-24-2015, 12:10 PM
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Originally Posted by ackroyd View Post
I must admit, I prefer high torque analogue servos, but then I'm only flying a mix of 40 size aerobatics and 1/4 WW1 fighters and a 1/4 Piper Cub.
analog are good the digitals just center better a lot more precise , piper cub is great and your analogs will be just fine on those great flying planes I was just showing how I set up my planes thanks Chris

Last edited by jmiles1941; 09-24-2015 at 12:14 PM.

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