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Old Mar 05, 2012, 10:54 AM
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Originally Posted by sandy11 View Post
No, you can't isolate Spektrum Rx reception power from servo load.

Spektrum's Design, 3S or lower
Motor Battery (11.1V source) --> (ESC BEC or external BEC (5V source) --> Servo bus (5V load) --> Rx reception (5V load)

Spektrum's Design, 4S to unnamed BEC capability
Motor Battery (unnamed BEC allowable V source) --> Unnamed BEC (5V source) --> Servo bus (5V load) --> Rx reception (5V load)

Hitec's Design, up to 10S
Motor Battery (11.1V to 37V source) --> Rx reception (5V load)

Spectrum's design will always lose reception given enough servo load. Hitec's will never lose reception given any servo load. That is a significant difference.
Oh, please, Sandy... just stop. This is getting utterly absurd. It's a significant difference only if it's true, and only if you design your flight system improperly. Use the proper sized battery, the proper sized BEC and be done with it. That's what everyone else does! I wonder how you can even fly, you make so many problems up.
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Old Mar 05, 2012, 11:08 AM
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Originally Posted by richard hanson View Post
Seems like HiTech has a feature I have never heard of----
Incredible
As a Spektrum user you probably haven't.........reliability.

All kidding aside, I think Sandy11 has gone off the deep end.
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Old Mar 05, 2012, 12:02 PM
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Originally Posted by erkq View Post
Oh, please, Sandy... just stop. This is getting utterly absurd. It's a significant difference only if it's true, and only if you design your flight system improperly. Use the proper sized battery, the proper sized BEC and be done with it. That's what everyone else does! I wonder how you can even fly, you make so many problems up.
"Oh please" sounds like your mind is closed. Perhaps you don't understand how voltage flows downhill if you can't see a major cost and risk difference.

Spektrum receivers, by design, reside down stream of a loaded 5V bus of limited amp capacity. They require 5V nominally, which means they will as in always, drop out given a high enough servo load. There is absolutely nothing that can be done about that because their only power supply is the servo bus.

Yes, one can mitigate the risk by buying a dedicated high amp BEC for 3S systems. According to Castle, that additional expense is required for 4S systems and higher. No one has attempted to clarify or refute Castle's statement for me, so I can only assume they know what they are talking about. That is an additional expense on par with buying the Rx itself, especially if you use more than a couple of digital servos which are notoriously power hungry.

Hitec's SPC port is isolated from the servo bus. The Rx runs directly on the 2S to 10S motor power battery. That provides a power reserve that equates to hundreds of times the nominal current flow, and two to ten times the nominal voltage requirement, so the Rx will always stay awake at no additional expense.

Maybe stating it more simply would help.

Every servo you add robs Spektrum Rx power, adding risk and requiring mitigation cost . Hitec Rxs run directly from the motor battery at no additional expense.
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Last edited by sandy11; Mar 05, 2012 at 01:38 PM.
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Old Mar 05, 2012, 12:24 PM
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Originally Posted by seefest View Post
All kidding aside, I think Sandy11 has gone off the deep end.
Agreed, his last post makes absolutely no sense...

He is also fixated on 5 volts for some reason.

I dont think he understands the typical Spektrum receiver operates from 3.5v9.6V, and while indeed its cool to have SPC power for your Hitec receiver, if a BEC setup is going to brown out on a Spektrum, im not sure how well those servos would perform (with that low voltage) on a Hitec regardless of how well the receiver is working.
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Old Mar 05, 2012, 12:27 PM
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Wow.Can anyone refute that this is the way Spektrum receivers are designed?
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Old Mar 05, 2012, 12:33 PM
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@ Sandy11 - That's awesome that Hitec have a receiver that can be powered seperatly from the power fed for the servo bus.

Great

Others protect themselves by ensuring proper power is fed to the rx and servos. I think we all have learned something today and you can change the subject. HIghly doubt any of us NON-Hitec users will switch over anytime soon based on what you have provided here today.
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Old Mar 05, 2012, 12:53 PM
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Quote:
Originally Posted by seefest View Post
As a Spektrum user you probably haven't.........reliability.

All kidding aside, I think Sandy11 has gone off the deep end.
I have had zero reliability issues (which is beside the point) but the explanation of voltage/servos and rx is -shall we say
a bit off the mark
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Old Mar 05, 2012, 12:56 PM
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So,in a Spektrum setup,the servos get fed before the receiver itself?
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Old Mar 05, 2012, 12:57 PM
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Originally Posted by freechip View Post
@ Sandy11 - That's awesome that Hitec have a receiver that can be powered seperatly from the power fed for the servo bus.

Great

Others protect themselves by ensuring proper power is fed to the rx and servos. I think we all have learned something today and you can change the subject. HIghly doubt any of us NON-Hitec users will switch over anytime soon based on what you have provided here today.
Thanks. I am a Hitec and Spektrum+BEC user too, I am brand agnostic but I know what costs me money/risk.

All that said, I find the reason for the above more interesting than the immediate consequences. I hope we can all agree that the Spektrum design is best described, not as "flawed" but rather "legacy." That is because it evolved from a "correct" approach formed back in the nitro days when there was only one source of electrical power in the plane, the servo/Rx pack.

The fact that Spektrum seems stuck using a clearly sub-optimum, pre-electric-motor-battery, legacy design is telling, if not damning. Frankly, it indicates that Hitec is thinking and Spektrum is not. Especially given that Spektrum's solution to a rather pandemic brownout probable has been to attack Rx reboot time instead of the root cause, apparently not realizing that another power source has commonly appeared since the days of all nitro. Spektrum needs to start innovating or they will continue to lose market share.
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Old Mar 05, 2012, 01:06 PM
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Quote:
Originally Posted by destinbeachman View Post
So,in a Spektrum setup,the servos get fed before the receiver itself?
A novel understanding of how power is shared
I think I see thereal problem here--
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Old Mar 05, 2012, 01:10 PM
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Does anyone have any more information about this?Is that description of how the receiver works correct or not?
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Old Mar 05, 2012, 01:30 PM
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Originally Posted by destinbeachman View Post
So,in a Spektrum setup,the servos get fed before the receiver itself?
Correct. When servo load draws the 5V bus below 3.5V, Spectrum generously (for themselves) calls that a brownout. It is of course a "blackout" because the Rx turns off when the voltage dips below the "brownout" voltage. Newer Spektrum Rx's have "quick reconnect" to speed reboot time but the link is still lost during the blackout. Here is how Spektrum describes it

Quote:
AR8000 Receiver Power System Requirements
Inadequate power systems that are unable to provide the necessary minimum voltage to the
receiver during flight have become the number one cause of in-flight failures.

Some of the
power system components that affect the ability to properly deliver adequate power include:
• Receiver battery pack (number of cells, capacity, cell type, state of charge)
• The ESC’s capability to deliver current to the receiver in electric aircraft
• The switch harness, battery leads, servo leads, regulators etc.

The AR8000 has a minimum operational voltage of 3.5 volts; it is highly recommended the
power system be tested per the guidelines below and in the Flight Log section.

Recommended Power System Test Guidelines
If a questionable power system is being used (e.g. small or old battery, ESC that may not have
a BEC that will support high-current draw, etc.), it is recommended that a voltmeter be used to
perform the following test.
Note: The Hangar 9 Digital Servo & Rx Current Meter (HAN172) or the Spektrum Flight Log
(SPM9540) are the perfect tools to perform the test below.
Plug the voltmeter into an open channel port in the receiver and with the system on, load the
control surfaces (apply pressure with your hand) while monitoring the voltage at the receiver.
The voltage should remain above 4.8 volts even when all servos are heavily loaded.
Note: The latest generations of Nickel-Metal Hydride batteries incorporate a new chemistry
mandated to be more environmentally friendly. These batteries when charged with
peak detection fast chargers have tendencies to false peak (not fully charge) repeatedly.
These include all brands of NiMH batteries. If using NiMH packs, be especially
cautious when charging, making absolutely sure that the battery is fully charged. It is
recommended to use a charger that can display total charge capacity. Note the number
of mAh put into a discharged pack to verify it has been charged to full capacity.

QuickConnect With Brownout Detection
Your AR8000 features QuickConnect with Brownout Detection.
• Should an interruption of power occur (brownout), the system will reconnect immediately when
power is restored (QuickConnect).
• The LED on the receiver will flash slowly indicating a power interruption (brownout) has occurred.
• Brownouts can be caused by an inadequate power supply (weak battery or regulator), a loose
connector, a bad switch, an inadequate BEC when using an electronic speed controller, etc.
• Brownouts occur when the receiver voltage drops below 3.5 volts thus interrupting control as the
servos and receiver require a minimum of 3.5 volts to operate.

How QuickConnect™ With Brownout Detection Works
• When the receiver voltage drops below 3.5 volts the system drops out (ceases to operate).
• When power is restored the receiver immediately attempts to reconnect to the last two
frequencies that it was connected to.
• If the two frequencies are present (the transmitter was left on) the system reconnects
typically within one second.

QuickConnect with Brownout Detection is designed to allow you to fly safely through most short
duration power interruptions, however, the root cause of these interruptions must be corrected
before the next flight to prevent catastrophic safety issues.


Note: If a brownout occurs in flight it is vital that the cause of the brownout be determined
and corrected.
I can't resist answering the part I bolded. Isn't the "root cause" Spektrum's legacy design?
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Old Mar 05, 2012, 01:33 PM
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All of the above is N/A for Hitec systems when using the built in SPC port which taps the motor battery directly.

This is also how Hitec Rxs know the motor battery voltage so they can telemitrate the info back to you on the ground.
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Old Mar 05, 2012, 01:39 PM
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But this would apply to all other NON SPC type rx which pretty much cover almost the whole hobby right?

Your focus should be on how great Hitec is and not how bad the others are.

If your cost of feeling safe with Hitec is less then with spektrum then so be it. I fly feeling very safe with my spektrum setups and the way I power them.
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Old Mar 05, 2012, 01:50 PM
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Originally Posted by freechip View Post
But this would apply to all other NON SPC type rx which pretty much cover almost the whole hobby right?

Your focus should be on how great Hitec is and not how bad the others are.

If your cost of feeling safe with Hitec is less then with spektrum then so be it. I fly feeling very safe with my spektrum setups and the way I power them.
This thread is called "Hitec Aurora 9 v.s Spektrum DX8." I spend a lot of money on external BECs so I feel reasonably safe using my DX radios too. But it's a lot more expensive. I used to use parallel external BECs for my more expensive planes but now, frankly, they run on Hitec.

Also I forgot to point out that Quick Connect only works for "most short duration" blackouts. If it is not "most" or "short" then the Rx goes into what the Hitec only users at your club jokingly refer to as auto-crash mode.
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Last edited by sandy11; Mar 05, 2012 at 02:00 PM.
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