Sky Surfer - aka Bixler See Post #2 & #3 for parts & mods B4 asking - Page 935 - RC Groups
Mar 27, 2012, 12:12 PM
Registered User
Quote:
 Originally Posted by ands Guys, just wondering how low you run your 2200's? Trying to get my head around the fact I can stay up for for than 8 mins as i have only ever flown warbirds. thanks ands
So many factors --- I finally got the FrSky telemetry transmitter module so I can KNOW what my cell voltage is.

### Images

Mar 27, 2012, 01:07 PM
Registered User
Quote:
 Originally Posted by ands Guys, just wondering how low you run your 2200's? Trying to get my head around the fact I can stay up for for than 8 mins as i have only ever flown warbirds. thanks ands
I "TRY" to run my 2650's to about 70% but it doesnt always happen so many different factors on each individual flight. Ive had LVC after 10mins and then Ive had to land after a 40min flight because I needed to rest my thumbs
 Mar 27, 2012, 01:21 PM CURIOSITY Has Landed! And sometimes ya need to neck and eye balls!
Mar 27, 2012, 01:41 PM
Registered User
Quote:
You mentioned that the Spektrum receivers have a tendency to brown out. Is that across the board for Spektrum or just specific receivers?

Does this issue happen in the Spektrum clone receivers or for that matter any other manufacturer of receivers?
Mar 27, 2012, 01:48 PM
Suspended Account
Quote:
Using the formula E/I = R, 4.5 volts devided by say 300 milliamps (receiver and 4 servos at very conservative demand) equals 15 ohms.

The formula for the RC time constant ( the time in which a capacitor dicharges through a resistance) is R times C in Farads. so 15 times 3,300 times 10 to the minus 6 = 49.5 milliseconds or .0495 seconds.

I'm trying to understand how it could hold the system up for 2 or more seconds. The current drain for the receiver alone is only about 9 milliamps so it could conceivably hold the receiver for about one second. What am I missing here?
 Mar 27, 2012, 02:00 PM Me a long time ago So what I have been saying is that those capacitors are a waste of time. If the brown out or signal lose is more than a fraction of a second... That's it. If you had some height and flying carefully such as in glide mode, the time the rx get a signal back say 2 seconds, then no harm will be done. As for reliability of Spektrum RXs.. There have been rumours about the unreliability. I have never experienced any problems and I have quite a few of them. Saying this I do like the HK Orange ones. Got a few of them as well.
Mar 27, 2012, 02:15 PM
Suspended Account
Quote:
 Originally Posted by Flypoppa So what I have been saying is that those capacitors are a waste of time. If the brown out or signal lose is more than a fraction of a second... That's it. If you had some height and flying carefully such as in glide mode, the time the rx get a signal back say 2 seconds, then no harm will be done. As for reliability of Spektrum RXs.. There have been rumours about the unreliability. I have never experienced any problems and I have quite a few of them. Saying this I do like the HK Orange ones. Got a few of them as well.
A brown out due to the BEC output voltage dropping below the receiver cutoff voltage is different than a brown out due to signal loss but the effect is the same. Regardless, in my opinion your first statement is correct, they are no help. Like you said only time and luck are your friends.

I also fly Spektrum and have only had one issue when a 6110 receiver totally failed in mid flight. Lost a plane on that one and HH gave me a new receiver. But never have had another problem with them.
Mar 27, 2012, 02:19 PM
FPV Electronics For Life!
Quote:
 Originally Posted by Flypoppa So what I have been saying is that those capacitors are a waste of time. If the brown out or signal lose is more than a fraction of a second... That's it. If you had some height and flying carefully such as in glide mode, the time the rx get a signal back say 2 seconds, then no harm will be done. As for reliability of Spektrum RXs.. There have been rumours about the unreliability. I have never experienced any problems and I have quite a few of them. Saying this I do like the HK Orange ones. Got a few of them as well.
Assuming your control surfaces stay good when it happens, but reality is brownouts are often caused by using the control surfaces, if you are in the middle of doing a fast turn and the draw of servos causes a brownout more then likely your control surfaces are NOT going to be at neutral when it browns it, it's going to be stuck in what it was.
Mar 27, 2012, 02:41 PM
Registered User
Quote:
 Originally Posted by Eagle202 You mentioned that the Spektrum receivers have a tendency to brown out. Is that across the board for Spektrum or just specific receivers? Does this issue happen in the Spektrum clone receivers or for that matter any other manufacturer of receivers?
All 2.4g receivers are more sensitive to voltage than Mhz systems. Spektrum receivers are more sensitive than the OrangeRX receivers in my experience.

That said, there's nothing wrong with Spektrum. You just need to use quality ESC's or a separate switching BEC. Spektrum receivers will flash if they experienced momentary low voltage. If they come down flashing, you need a better power supply to the receiver.
Mar 27, 2012, 04:13 PM
Registered User
Quote:
 Originally Posted by ands Guys, just wondering how low you run your 2200's? Trying to get my head around the fact I can stay up for for than 8 mins as i have only ever flown warbirds. thanks ands
I can run up to 30 min on my 2200s depending on throttle usage with a 450 Watt setup. Granted, I do a fair amount of gliding, so your mileage will vary.
Mar 27, 2012, 04:29 PM
Registered User
Quote:
 Originally Posted by buracho Using the formula E/I = R, 4.5 volts devided by say 300 milliamps (receiver and 4 servos at very conservative demand) equals 15 ohms. The formula for the RC time constant ( the time in which a capacitor dicharges through a resistance) is R times C in Farads. so 15 times 3,300 times 10 to the minus 6 = 49.5 milliseconds or .0495 seconds. I'm trying to understand how it could hold the system up for 2 or more seconds. The current drain for the receiver alone is only about 9 milliamps so it could conceivably hold the receiver for about one second. What am I missing here?
Buracho, your missing nothing. I just measured the current drain from 4 HK Orange 6 ch. rcvrs., and 1 Spektrum 6100e 6 ch. rcvr. and the AVERAGE
current drain for those 5 receivers was 23.5ma. @ 5.01V input from the ESC. Using those figures, it would be absolutely impossible to maintain the terminal voltage of a 3300uf capacitor at 4.8V as stated in the previous post by AJ. In just 1 RC time constant, approx. .7secs., the terminal voltage of the capacitor would be about 1.84V. That's far below the "requisite ~4.8v for ~2 seconds so the receiver does not reset" as claimed by AJ. He also states that in a practical application, and his own bench testing, that a 3300uf capacitor will furnish enough current for 4-5secs. That must be some very special 3300uf cap that he's using.
Mar 27, 2012, 04:55 PM
Registered User
Quote:
 Originally Posted by Ole Joe Buracho, your missing nothing. I just measured the current drain from 4 HK Orange 6 ch. rcvrs., and 1 Spektrum 6100e 6 ch. rcvr. and the AVERAGE current drain for those 5 receivers was 23.5ma. @ 5.01V input from the ESC. Using those figures, it would be absolutely impossible to maintain the terminal voltage of a 3300uf capacitor at 4.8V as stated in the previous post by AJ. In just 1 RC time constant, approx. .7secs., the terminal voltage of the capacitor would be about 1.84V. That's far below the "requisite ~4.8v for ~2 seconds so the receiver does not reset" as claimed by AJ. He also states that in a practical application, and his own bench testing, that a 3300uf capacitor will furnish enough current for 4-5secs. That must be some very special 3300uf cap that he's using.

A brown out is nothing more than a voltage dip. The electronics to maintain or regulate a constant voltage is comprised of more than capacitors.

My guess is that the receiver electronics has some sort of voltage regulation circuit already inside. Using the calculations above does not take that circuitry into the equation.

Adding a capacitor to the circuit provides a place to store voltage. How the capacitor discharges that stored voltage is based on the other circuitry in the receiver. So the voltage levels and discharge duration may not be so easily calculated without knowing the rest of the circuit since it is not just a resistor.

Vince
Last edited by Eagle202; Mar 27, 2012 at 04:58 PM. Reason: sign off
 Mar 27, 2012, 05:13 PM ICrashRCs my layman's guess, The voltage shortage is normally fractional. The reset time is the big delay. If the capacitor avoids the voltage shortage, there is no multi second delay. For me the question would be, How long does the voltage shortage actually last?
Mar 27, 2012, 05:22 PM
Quote:
 Originally Posted by buracho Using the formula E/I = R, 4.5 volts devided by say 300 milliamps (receiver and 4 servos at very conservative demand) equals 15 ohms. The formula for the RC time constant ( the time in which a capacitor dicharges through a resistance) is R times C in Farads. so 15 times 3,300 times 10 to the minus 6 = 49.5 milliseconds or .0495 seconds. I'm trying to understand how it could hold the system up for 2 or more seconds. The current drain for the receiver alone is only about 9 milliamps so it could conceivably hold the receiver for about one second. What am I missing here?
What you are forgetting is the current already present from the ESC (actually, the BEC portion of the ESC.) That current is anything but constant and therefore not totally predictable. I can tell you from practical testing that using larger caps, I can get 8-12 seconds of "battery time" (for a receiver and one servo) from a charged capacitor .
AJ
Mar 27, 2012, 05:25 PM

# An ounce of prevention

Quote:
 Originally Posted by Flypoppa So what I have been saying is that those capacitors are a waste of time. If the brown out or signal lose is more than a fraction of a second... That's it. If you had some height and flying carefully such as in glide mode, the time the rx get a signal back say 2 seconds, then no harm will be done. As for reliability of Spektrum RXs.. There have been rumours about the unreliability. I have never experienced any problems and I have quite a few of them. Saying this I do like the HK Orange ones. Got a few of them as well.
Not exactly. The capacitor prevents a brownout from occurring. It is like having a bigger battery on board to stop any brownout BEFORE it occurs.
AJ