AirmanBob

My Feedback: (14)

Why is it that only Spektrum receivers have brownouts?

I've flown Futaba every since the first ones came out and

I've never had a brownout. I bought my first Spektrum

this week and I'm a little worried that I'm gonna start

crashing all the time. I know, I know... put in a bigger

battery and all's good...maybe....

The people that build the chips for Spektrum should lower

the cutoff voltage somehow. That way, the servos would start

moving slowly and we'd know that the battery was low.

Just curious... not trying to start a Futaba vs Spektrum war.

Bob

BuschBarber

My Feedback: (2)

I have been flying Spektrum for the past 4 years and I never had a Brownout. When the problem was first identified and reported to Spektrum, they updated the Firmware so the Reboot time, of the Rx, was 1/2 sec instead of 4 sec. They subsequently added a feature that displays a Blinking Light, on the Rx, that indicates the Rx experienced a Power Loss. There is no reason to fear JR/Spektrum, Futaba, Hitec, Airtronics, or any other 2.4Ghz RC radio product.

By the way, Futaba Rx's can Brownout if the Voltage Drop goes to Critical.

airbusdrvr

Why not operate with proper sized and charged batteries? Then you would not have to be concerned if it is 3.3V or 2.8V that the receiver quit working. Moot point, though, the servos probably don't do much at 3V, either[>:]

Silent-AV8R

Huh? A Futaba FASST RX will not "Brownout" in the manner the Spektrum stuff did/does. What happens is if the voltage drops to somewhere are 2.8 volts or so the RX will shut down as if the power was turned off. It will immediately turn back on once the voltage recovers. The issue with the Spektrum stuff was that the recovery time often exceeded the time it took for the plane to find Mother Earth.

To get to that low of a voltage means that something is very wrong in your battery. FWIW some brands of digital servos stop working all together at 3.0 volts.

DougV

But before you get to those low voltages you will get warned by the battery fail safe (throttle only will go to F/S at 3.6v) feature with the Futaba rx’s.

Just use good batteries and you will be fine.

Doug.

BarracudaHockey

My Feedback: (11)

Brownouts can occur with any radio, they aren't specific to 2.4 or Spektrum

The main issue is that in the old days if something dragged the voltage too low it would show up as glitch. As others have noted, with 2.4 and more complicated systems, instead of glitch we got a reboot which took several seconds. Depending on where you are when that occured it could be more than enough to cause a crash. Now it happens lightning fast.

But just because you didnt know you were having a problem with an inadaquate power system didn't mean you weren't having one.

An adaquate power system is a good thing no matter what type of radio system you're using.

BuschBarber

My Feedback: (2)

As I mentioned in my last Post, the Reboot time, after a Brownout, for a JR/Spektrum Rx is significantly less since the Firmware change was implemented. Brownout or Power Out it still sounds like the Cause and the Reboot time is much the same with Futaba.

I use LiPo, LithIon, or LiFe 2cell Rx packs, with a voltage regulator for either 5v or 6v depending upon my servo choice.

You can test your system, to determine if it can suffer from this condition, by hooking up a Wattmeter or an H9 Current Meter, between the Rx Battery and Rx, and then Stall all the servos, manually, with the help of a friend. This should create the Worst Case Scenario and help you determine if you need to use larger Rx batteries. The Current and Voltage measurements should be helpful.

Silent-AV8R

However, you are giving an incorrect impression. There have not been any reports of power related failures similar to what the JR/Spektrum equipment experienced. It is simply incorrect to give the impression that both are equally susceptible.

K-Bob

My Feedback: (1)

You will get some indication of a problem with Futaba long before you reach the 2.8v cutoff. The throttle failsafe has already been mentioned but your first indication will be s-l-o-w servo speed. I had this happen recently with my 42%er. I had flown 3 flights with only one battery (2300 Mah A123) connected. On the 4th flight I noticeed very slow aileron speed and landed to check it out and found the diconnected battery. I never lost control of the plane and the link was, as always, rock solid.

BuschBarber

My Feedback: (2)

I am not trying to bash Futaba and I have no first hand knowledge that Futaba has had reportable incidents of Brownout like conditions. You just said, in one of your posts, that Futaba Rx's will ReBoot if the Rx voltage gets too low. How is that not the same thing that is reportedly happening to JR/Spektrum Rx's?

Every manufacturer's radio is going to experience a problem now and then. The problem is addressed by the manufacturer and we move on.

It seems that because there is fierce competition between radio manufacturers, the best way to encourage someone to buy one product over another is not to compare products, feature by feature, but to scare them away from the other product with stories about Defects.

rmh

[quote]ORIGINAL: Silent-AV8R


Huh? A Futaba FASST RX will not ''Brownout'' in the manner the Spektrum stuff did/does. What happens is if the voltage drops to somewhere are 2.8 volts or so the RX will shut down as if the power was turned off. It will immediately turn back on once the voltage recovers. The issue with the Spektrum stuff was that the recovery time often exceeded the time it took for the plane to find Mother Earth.

I think you have not tested this idea.
here is why: Once a battery -in use, reaches "departure voltage", The computer based radios (ALL OF EM) shut down till voltage rises above this threshold .
here is where the sh hits the fan.
The radio reconnects and the rx sends info to servos to assume commanded position
This causes another sudden voltage depression-which causes another shutdown- which again allow a slight voltage rise -which again allows system to reconnect.
You can proove this with a bench test using a small battery which is just above minimum output level.
Depending on the servos used and the battery used th system will slowly go off -then on -etc..
with rapid current drain servos -th result may be wild servo excursions as the rx goes - of servos go to hold -batt rises a littl e then shuts down as soon as a load is applied.

BuschBarber

My Feedback: (2)

Generally, when the Rx loses power, there is no Failsafe Event. A Failsafe Event is usually triggered by a Loss of Signal, from the Tx, or Interference.

Are you saying that Futaba Rx's will go into Failsafe when the Rx voltage drops to a certain level, but before power is lost to the Rx? Is that true with all Futaba Rx's?

I remember, in the 80's, when a pilot I was assisting had an Rx battery that was loosing voltage and the servos became very sloooooow, almost uncontrollable, but I still could just barely control the aircraft and land it. This was on 72Mhz.

DadsToysBG

My Feedback: (35)

All these discussions about brown outs reboot times are all related to battery maintenance. W ether or not one radio is faster then another is not important. If the consumer takes such poor care of his battery's how can they fault any radio company. Spektrum found a issue with their reboot system and corrected it. It's still the users responsibly to keep the battery charged. Dennis

rmh

My example had nothing to do with signal failure -which is tied to "failsafe"
The type of battery will determine how severely the voltage depression will be under servo load. Take a classical "my radio quit " scenario - the user says
"I was flying my electric model and all was fine for about 2 minutes -then it went crazy -I thought I got it back then it quit - after landing I could find nothing wrong -it worked OK."
Possible actual scenario:
model takes of at full throtle and is subject to a lot of throttle operation- The LiPos feeding the system finally drop voltage -and FWIW some packs will die quite rapidly under constant burst inputs.

The radio quits -tries to go again as surface voltage comes up - servo load now drops power again - then the crash .
checking it on the ground - voltage is now above threshold and testing shows it all works .
This is all possible and probable and is likely the cause of many "unexplained" failures - blamed on the radio.

Rodney

Brown outs can be caused by things other than an insufficient battery. The wiring between the battery (no matter how good or big the battery) can cause a brown out or momentary drop out if there is a high impedance in the path such as a switch that has corroded, a battery cable that has been damaged and had its cross section area decreased (like broken strands or poor crimp or poor solder joint) or a servo hanging up and drawing excessive current. That is why a Voltwatch or equivalent indicator is nice to have as, when you exercise the servos by rotating all sticks at one time and watch the indicators, if you see a red LED flashing, you have a problem as you are getting momentary voltage drop outs at the point the indicator is plugged in.

A.T.

Further to Rodney's comment,
Problems with EP's and "Brownout" also relate to the ESC which have an incorpirated BECin use.
AOKupto 3SLipo and only two servo but many models now have multiple servos and the built in BECcan not handle the demand and cuts power supply to RX, refer
Electronic Speed Control - Why BEC and LVC cause most EP RX problems
Which is why telemetry is now a must haveon modern TX in order user can catch bad batteries, BEC or bad servo before and whilst flying.
Some users insist on using cheaper servos which are cheaper because of the poorer quality motors and thus high current drain, especially on startup which drags voltage down.
<dt>Servo - FAQ -Peak Servo Current Test Results.

With regard to the larger GP models:
1. NiMH simply do not provide the current produced by NiCds as required with multi servo models.
"1. "two 6 volt 3000 mah nimh" must be at least "C" size ex quality high discharge racing car packfor a 50cc model."
2. AA 3000 NiMH have a high internal resistance and fail under high current demands. Standard AA NiMH are not recommended for models above .60.
3. Voltage Telemetry- The last saved low battery voltage may not be correct for A123(&LiFE).
The refresh rate is about 0.5sec so even in brownout situations,it shows the last voltage reading when it cycled.
A123's (&LiFE) when they dump the voltage falls off the table unlike Nicad/Mh which have a more gradual voltage loss.
4. If not using a separate solid power bus on large models, use two or more HD switches and leads, "Y" with servo in need.
Standard S-01, Fut J or JST plugs form a power bottleneck, so load must be spread through more than one plug/port.
Optima Transceiver (RX) - Battery set up for Nitro/Gas models - caution re NiMH & Alert re LiFE.
Optima Transceiver (RX) - Dual or Multiple Batteries may be installed - Avoid Brownout & Add Redundancy, even one for each servo.

. SPC port is a must for EP models, not necessary for GP models where you want to monitor power to your servos -
Optima Transceiver (RX) - SPC - SPC connection & Lead Detailed
". LiFe vs NiMH Receiver battery tests
"It's becoming well known that the 2.4 Ghz radios may be susceptable to undervoltage issues on the receiver battery supply. And, these have resulted in loss of control of the model. Spektrum did do some software updates a while back to reduce the time of "Rebooting" in case of a low battery issue. My testing on updated AR7000 receivers shows this "rebooting time" is less than a second.
IMHO, this is not a receiver issue, it's a problem with the receiver battery selected. By actual test, I've measured the peak currents pulled by all 7 Hitec 645MG in my giant scale Extra 330 model. That peak current was measured at 14 amperes, with the one millisecond peak holding feature of my Fluke 87V digital multimeter.
So, to illustrate this issue, two discharge current tests of 12 amperes were applied to a new LiFe 3200 Mah battery, and to a new 5 cell 2700 Mah Nih "AA" type receiver battery.
The attached graph, taken from my Western Mountain CBAIII battery test unit shows it all.
Take a look at the attached JPG: The 12 Amp load on the Nih battery was shut off when the voltage dropped to 3.6 VDC, a value reached in about 2 seconds. Note that those Spektrum receivers will reboot when the receiver battery voltage hits 3.2 VDC. The Nih battery test was conducted immediately after it was fully charged. The results will be worse after a few flights on the model.Again, IMHO, the 2.4 Ghz receiver of any large model with more than 4 servos and a receiver battery should be using a higher powered receiver battery than those "AA" type units. Recommendations would be one of those LiFe types, a "Sub C" 5 cell Nih battery, or a uBEC such as Castle Creations 10 (or 20) Amp Switching Battery Elimination Circuit."

See also a very good article:
Brownout and Voltage Drops - by Mike Mayberry - Hitec rep.

and more under
Alan's Hobby, Model & RC FAQ Web Links

Alan T.

</dt>

Rob2160

Been flying Spektrum for 12 months, 2 x Dx6is, 1 x DX8, multiple BNF aircraft, helicopters, etc...

Never EVER had a problem.

Brownouts will occur with any RX - it is a battery / BEC issue, not an RX issue.

Feed your receiver the power it was designed for and you will never have a problem.

Its like having a dead battery in your car and blaming the Starter motor when the car won't start!

DenverJayhawk

flew a DX6i for two years and never had one brown out problem. I flew both electric and glow, with BEC and without. On glow, i flew with both a 4 cell and 5 cell rx battery pack with no issue. I used everything from AR6110e, AR500s, and AR6200s. Brownouts occur when people are either: 1. too lazy to charge their rx packs the night before flying or 2) they forget to do it and fly anyway or 3) they have a bad batt pack and didn't range check. Either way, it's pilot error.

PS....Spektrum demonstrated with video that their brownout recovery on the current firmware recovers quicker than the "competitor" brand.

pilotpete2

They had to pull that video when it was found that they used a first generation, out of production receiver to make their case
Fact is, that in most instances a momentary loss of power to a FASST, DSM2 (quick reconnect), or DSMX receiver will hardly be noticeable to the pilot, unless the power drop is of long duration or keeps cycling on/off. Like what happened to me with a bad solder joint in a switch harness, I knew something was wrong, but the very early version FASST receiver handled it in stride. I got to troubleshoot the problem on an intact airframe, rather than a post mortum[8D]
DSM2 lockouts due to power brownout ended with the introduction of quick reconnect firmware. The less common RF fade induced lockouts with DSM2 (more common with low end receivers) was fixed by DSMX. Oh wait, I forgot, DSMX is only really important to folks that fly at large events, right
Pete

DougV

What was demonstrated on that video by John Adams and Spektrum is that the current firmware will reconnect just a little faster than the old Futaba R606FS receiver (discontinue for about 4 years)
By the way, one of the reasons why the R606FS was discontinue was because it was too slow to reconnect (almost 1.5 seconds) compared to the R617FS (instant reconnect)

Makes me wonder, why John Adams didn’t do an apples to apples comparison test, like the R617FS and the AR7000? Which by the way, I own both.

Doug.

AirmanBob

My Feedback: (14)

Well I guess my point is.... there was no such word as 'brownout' until after Spektrum

came along.

I started out using the old "Citizenship" brand radios with just one channel and a rubber

band powered escapement. The receiver had a "tube" instead of transistors and some of

my equipment required 45 volt batteries. Later we 'upgraded' to reed tuned radios. Made

by 'Bonner' I think. Lots of mechanical problems. Finally, we started using the modern day

72mhz systems and I tried just about every brand that came along.

I never had a so-called brownout. That is probably why flyers from that generation became

a little lazy about battery management. I flew with some very old, tired batteries and never

had a 'brownout' .... The controls would get lazy and sluggish but I always managed to land

safely. I've never had a plane just shut off in the middle of a flight.

I don't know why they would design a receiver to do that. If I want to fly my batteries till

they are nearly flat I should be able to. And, the receiver should be the STRONGEST link

in the system, not the first thing to quit... doesn't make any sense to shut it down.

I'll go ahead and use the dx6i for my park flyers because I like the bind-n-fly feature.

But, Spektrum needs to fix the receiver so that its the LAST thing to slowly fade away.

And that's my 2 cents worth... hopefully Spektrum reads this stuff.

Bob

rmh

Bob- Your "hope" is not going to happen.
Spread Spectrum (SPEKTRUM introduced it to model fliers), is a computer based system -
The concept is nothing like the old radios you mentioned -
Just like ANY computer based system, it is a digital system which requires startup procedures and must maintain a particular voltage level to keep operating - if power drops it MUST start over -that reconnect can be very fast but it is not a "fade away"..
You can't make it fade out n fade back in .
That is grossly simplified -but thats how it operates.
PS the Futaba - all of em operate the same way - there is no servo fade out then rx fade out
There can be a lower voltage trigger point which will cause an alert - such as throttle shut down -which can be operator restarted but that's the only safety I know of other than a servo "hold"
SPEKTRUM does use a low voltage trigger " to connect a light on the rx which remained on as a notice the radio had seen a lower than acceptable voltage spike -or shut down and restart. This is used on some DSM2 systems.
failures in power systems is still # 1 cause of "radio failure" in these spread spectrum systems
Why?
operator error typically due to lack of familliarity with how these systems operate -at a user level..

AndyKunz

Wish is granted - we DO read this. However, rmh's explanation is right-on as to why you won't see a receiver which runs to infinitely low voltages. BTW, an analog rx needs a certain voltage to operate, too. It's just a different voltage. PCM receivers had the same issue as modern receivers - they have a computer chip in them that needs enough volts to work. Chances are, though, that you don't have high-current servos and an undersized BEC in your PCM-based airplane...

Andy

airbusdrvr

Click and Clack the Tappet Brothers who do the Car Talk show on PBS each saturday have an appropriate saying for those RCers who continue to blame battery issues on the radio. "Non impediti ratione cogitationis." Or in English, "Unencumbered by the thought process." And that is my 2 cents worth.

Silent-AV8R

It also demonstrated that JR digital servos will stop operating at 3 volts. The older Futaba RX did not lose link, but the servos stopped operating. Which is good information for those using JR servos with their Futaba FASST systems. With respect to voltage it is the servo that is the limiting factor.