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  1. #26
    rmh's Avatar
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    RE: Brownouts....


    ORIGINAL: airbusdrvr


    ORIGINAL: AndyKunz


    And that's my 2 cents worth... hopefully Spektrum reads this stuff.
    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
    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.
    Apparantly Click n Clack don't fly RC-
    The reason battery issues are blamed as number one issues is very easy .
    Power to the rx IS the largest factor in problems with 2.4 radios
    May not be the battery -may be a regulator -may be wiring - may be an overload due to a myriad of reasons
    Bottom line - power fails and that is referred to as a "battery " problem.

    If you have any information to counter this - it would possibly be helpful.
    Libby is still watching you

  2. #27

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    RE: Brownouts....


    ORIGINAL: rmh


    ORIGINAL: airbusdrvr


    ORIGINAL: AndyKunz


    And that's my 2 cents worth... hopefully Spektrum reads this stuff.
    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
    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.
    Apparantly Click n Clack don't fly RC-
    The reason battery issues are blamed as number one issues is very easy .
    Power to the rx IS the largest factor in problems with 2.4 radios
    May not be the battery -may be a regulator -may be wiring - may be an overload due to a myriad of reasons
    Bottom line - power fails and that is referred to as a ''battery '' problem.

    If you have any information to counter this - it would possibly be helpful.
    I think I do not understand the direction of your post. Are you saying low/no voltage is an electrical issue or a receiver issue?
    UltraSport Brotherhood #17

  3. #28
    rmh's Avatar
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    RE: Brownouts....

    ORIGINAL: airbusdrvr


    ORIGINAL: rmh


    ORIGINAL: airbusdrvr


    ORIGINAL: AndyKunz


    And that's my 2 cents worth... hopefully Spektrum reads this stuff.
    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
    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.
    Apparantly Click n Clack don't fly RC-
    The reason battery issues are blamed as number one issues is very easy .
    Power to the rx IS the largest factor in problems with 2.4 radios
    May not be the battery -may be a regulator -may be wiring - may be an overload due to a myriad of reasons
    Bottom line - power fails and that is referred to as a ''battery '' problem.

    If you have any information to counter this - it would possibly be helpful.
    I think I do not understand the direction of your post. Are you saying low/no voltage is an electrical issue or a receiver issue?
    2.4 receivers - becaause they are mini computers, are extremely responsive to voltage levels.

    Once they are up and running the primary reason they may fail,quit, reboot is a low voltage issue.
    Using a current 2.4 setup which is prone to interferrence is a very slim probability.
    So unlike previous systems where we had frequency interferrence - noise interferrence - both internal and external as very real problems the modern 2.4 spread spectrum radio really has one major issue - power to the system must be up to the task.
    One may believe one brand 2.4 is more or less prone to voltage issues than others -
    makes no difference
    All 2.4 have this as the major reason for problems
    Libby is still watching you

  4. #29

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    RE: Brownouts....

    I could not agree more with post #28 above
    UltraSport Brotherhood #17

  5. #30
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    RE: Brownouts....

    Hmmm.... I think I'm begining to see a trend here...

    It seems there is a price to pay for using DIGITAL computerized equipment. Digital

    eats batteries... So I'll upgrade my batteries and see how it goes.

    Thanks to all for the good input....

    Bob

  6. #31
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    RE: Brownouts....

    But, getting back to the brownout problem...

    They build some very powerful computers these days

    with CPU's and memory chips that run on 3.3 volts or

    less and they expect in the near future that they will

    run on half that voltage. And, my pentium computer never

    browns out. It gets really hot sometimes and slows way down

    but it doesn't just shut down. I know... I know...its because it has a good power supply.


    So, my wife wants to know why is the spektrum computer chip such a power hog?

    She's kind of nosey...but nice.

    Bob

    Bob


  7. #32

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    RE: Brownouts....

    pretty hard to brown out a123 batteries. specktrum destroyed three airplanes no fail safe etc the first recievers didnt go into fail safe etc pretty hard to sell me the new improved version. yes they work better but still hear same problem no throttle down no control and enough time to verify no control.

  8. #33

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    RE: Brownouts....

    Here is what works for me to see if there is a problem with the power to the receiver. (Note, I said works for me)

    I load the surfaces by hand to get a high current draw from the power source. At the same time I am watching the receiver voltage with a storage scope. (And I know not everyone has a scope). This will give you a lot more information than a volt-watch or a loaded voltage meter because they only give you an average of what is going on and are not fast enough to catch a quick voltage problem. A storage scope shows it all on what is going on with the supply and has saved me from having a problem.

    Some things I have learned are. Some regulators will dip in voltage and recover during a current spike. They are not quick enough to keep up with a high current inrush. I have also seen a voltage dip with some NiMh batteries. Both of these cannot be seen with a loaded meter looking at the battery because they are just not quick enough. Some servos have a very high inrush current as the motor in them just starts. I’ve only been able to see this with a scope.

    What I would like to know is how many mSec the voltage must be under the limit to get the receiver to reset. I know this is why some people put a 1000 uF cap on the receiver supply line in an unused servo channel. To me this only masks the problem of the power to the receiver.

    Again, I know that most people do not have a scope to check the set up of the supply in a model. I’m just passing on what I have learned.

    Pete

  9. #34
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    RE: Brownouts....

    All readers __and Pete of course who already knows what follows . . . . .

    A "so called brownout" occurs when the supply voltage to the receiver / servos supply voltage drops below a specific voltage.

    That voltage value may vary depending on the receiver in use.
    This minimum voltage should be available from all receiver manufacturers.

    The time (delay for a brownout to occur) may also vary) and I have never seen a figure for that.

    The supply voltage (battery or ESC) drops at high current surges due to the internal resistance of the supply source.

    The presence of a high capacity condensor (capacitor) helps because the capacitor has acquired a charge (the more capacity in ufd (microfarad, a unit of capacity) , the more coulomb in the capacitor).

    A coulomb is a unit of amount of electrical charge stored in the capacitor.

    The capacitor has nearly negligeable internal resistance and can maintain the voltage (prevent an instantaneous voltage drop) for a short time. In different words, the capacior can supply the high peak current that would cause the supply source with high (relatively) internal resistance to drop.

    NOTE:
    Posted to help those less knowledgeable in electrical behavior of our circuits.

    At the moment of closing the switch, the capacitor acts as a nearly short circuit to the voltage / current supply until it charges to the voltage of the supply source. That is very rapid and itself creates a high current surge to the supply.

    If the source is an ESC we must assure that the ESC is not damaged by such a surge of current charging the capacitor.

    ESC data does not cover this to my knowledge.

    Zor


  10. #35
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    RE: Brownouts....

    The theory behind caps is fine -but for our use in airplanes - -it ain't the way to go .
    There simply is no enough capacity (pun) to solve the real problem which is voltage fading (from old/undersized battery) or from over heated regulators (which recover slowly)
    Over and over -I see reports on line of the 2.4 radio which runs for 4 minutes in flight -then the rx fails -
    Or similar such stories.
    You can bet that the real issue in thes cases is voltage depression -for what ever reason
    these 2.4 rx are not like th rx of old . These work -or they don't work - no half way stuff- except for some early on 2.4 stuf which overheated
    Libby is still watching you

  11. #36
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    RE: Brownouts....

    The capacitormay beuseful only for very short current overloads if the receiver brownout occur in a very short time.

    It is not of any help for worn out or discharged batteries.

    Zor

  12. #37

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    RE: Brownouts....

    stick with futaba cnt go wrong i have been using futaba since the early eighties and still using there product now have a10cag 2.4 and 8fg super love both these radios.

  13. #38

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    RE: Brownouts....

    Over the past 2-3 years, several Hanger 9 Alpha trainers with the Spectrum DX5 transmitter have been lost to "brownouts" at my flying field. I do not think this is all due to undercharged batteries as many of the same pilots fly other transmitter brands without issue.

  14. #39
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    RE: Brownouts....

    If the problem is a brownout - it is a power problem-
    may be battery maybe not but it is a power problem.
    Libby is still watching you

  15. #40

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    RE: Brownouts....


    ORIGINAL: ramboy Over the past 2-3 years, several Hanger 9 Alpha trainers with the Spectrum DX5 transmitter have been lost to "brownouts" at my flying field.
    I do not think this is all due to undercharged batteries as many of the same pilots fly other transmitter brands without issue.
    Were they using a switchmode regulator or ESC/BEC? not see any problems when using a quality UBEC.
    Now never fly an EP model with more than 2 servo irresepctive of the BEC rating shown on an ESC.
    . Electronic Speed Control - Why BEC and LVC cause most EP RX problems.

    Much more under sub sections
    "ESC & BEC - Setup to prevent majority of all RF Problems, Brownouts & Crashes"
    "Glitches & Jitter in Receiver, Servo & ESC - Causes and Cures"
    below
    "Radio Systems, Accessories, Alterations and FAQ" at
    Alan's Hobby, Model & RC FAQ Web Links

    Alan T.
    R/C hobby consultant for various companies

  16. #41

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    RE: Brownouts....

    There have been several cases (one of them mine) where the DX5 stopped transmitting yet the green LED stays on. This has been traced to an intermittent power switch. similar problems have also been documented in the forums. Could this have been your problem?

  17. #42
    rmh's Avatar
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    RE: Brownouts....

    If it was- how was it detected ?
    If you know
    Libby is still watching you

  18. #43

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    RE: Brownouts....


    ORIGINAL: rmh

    The theory behind caps is fine -but for our use in airplanes - -it ain't the way to go .
    There simply is no enough capacity (pun) to solve the real problem which is voltage fading (from old/undersized battery) or from over heated regulators (which recover slowly)
    Over and over -I see reports on line of the 2.4 radio which runs for 4 minutes in flight -then the rx fails -
    Or similar such stories.
    You can bet that the real issue in thes cases is voltage depression -for what ever reason
    these 2.4 rx are not like th rx of old . These work -or they don't work - no half way stuff- except for some early on 2.4 stuf which overheated
    A cap is not going to cure a chronic lack of current issue.I cant dispute that.I have found that as we are running equip with higher intermittent/instantaneous current demands that a larger cap can dramatically smooth out voltage ripple.I may be wrong but I kind of tend to think as we put more demand on the power aspect of our systems that it may become more prudent to examine ripples created by intermittent use of lots of current in various setups.I kind of think that it is something that cant be defined as a "one size fits all" setup but in some cases it may be something to examine.

    Ill send you a mail to discuss some of my findings when I get a chance.

  19. #44
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    RE: Brownouts....

    Wow you guys Play pretty nice and fair. Was hoping to see a big puddle of blood on the ground towards the end of this post.

  20. #45

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  21. #46

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    RE: Brownouts....

    "Analog" RX's and servos in the "old" days were more tolerant of voltage, and might continue to work when the newer RX's and servos do not.
    The evidence is simply nothing more than the types, voltages, and capacity of the RX battery, then and now.
    A four AA cell 600mah NiCad  battery was the standard for quite some time. Going back to the 70's or so, the RX battery was even "center tapped" on at least some of the radios. I still have one RX and some Kraft design servos that require the center tap. The servos are quite slow by today's standards. The RX is a discrete classic solid state design, with dual conversion.  Generally, transistor receiver design started out in the 50's using a  9 to 15(or so) volt battery, and as time went on, the required battery voltage dropped that supplied by a one or two cell AA battery.

    Moving on, 2.5v to about 6v was a fairly common voltage used to supply digital circuitry in the late 60's and early 70's, as the RX's started including digital circuitry. Digital circuitry in general has higher peak current requirements than an analog circuit that might be used to do a similar function.  This was rather obvious, as Digital IC's often have have a small value capacitor located quite close to the IC. This capacitor provides the peak current needed during the transition from one logic state to another.

    Moving further on, it's rather obvious that today's RC RX's and servos  require far more peak current and a higher voltage for proper operation.
    Further, the "better" batteries have a flatter voltage/current capability. Unfortunately, the price is less notice when the battery is approaching an unusable level of charge.

    Many of the current RC battery checkers do not "load' a battery, or the load is not enough.
    I believe that a good battery checker should have a minimum load, and a push button activated load of at least one Amp, preferably up to two Amps. 



     

  22. #47
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    RE: Brownouts....

    You are right -
    The problem is that some fliers believe that if their servos don't pull 2 AMPS - Why test for two amps.
    This puts us squarely into Batteries 101 and some guys just don't want to have to learn the basics.
    Libby is still watching you

  23. #48

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    RE: Brownouts....

    The best battery in my opinion for our new systems are the A123's. you can get them in 3 cell @ 23 to 2500ma or for the smaller planes they have then in 2 cell 1100ma. Dennis
    DadstoysRC. I fly what I sell
    CD Vette City Big Bird

  24. #49

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    RE: Brownouts....


    ORIGINAL: DadsToysBG

    The best battery in my opinion for our new systems are the A123's. you can get them in 3 cell @ 23 to 2500ma or for the smaller planes they have then in 2 cell 1100ma. Dennis

    Add good switches and sufficient wire size and you are good for the go.


  25. #50
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    RE: Brownouts....


    ORIGINAL: DadsToysBG

    The best battery in my opinion for our new systems are the A123's. you can get them in 3 cell @ 23 to 2500ma or for the smaller planes they have then in 2 cell 1100ma. Dennis
    1100 and 25/2300's are 2 cell, they are just different size cells.
    Andy - Helicopter Forum Moderator
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