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Old Nov 05, 2012, 02:21 PM
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Quote:
Originally Posted by richard hanson View Post
Electric models?
A seperate rx source for larger stuff to be sure However overvoltage with a reg is -my opinion not as good as direct power to rx.
On Spektrum- either direct 2 cell LiPo or best , direct power A123.
Regs are just one more failure point and large difference in voltage between source and output voltage creates BIG problems
This is why most ESC for over 6 LiPo will not have internal BEC output
One of the worst setups ever -my opinion- was the LiIons with linear regs -and fans- These failed in a sneaky fashion -just as do th cheezy ESC on the market - the BECs (regs) - overheat - quit - then appear fine once cooled.
The switching BECs I use are very reliable! They have ZERO voltage drop under load, that's why I suggested they might be better. I don't use the type of receivers which can handle a 2-cell Lipo directly. The linear regulators have problems with heat, and the higher the source voltage, the worse that problem gets, but the switching regulators have no such issues. I agree it is a potential failure point, but the trade off is you get much more stable voltage.
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Old Nov 05, 2012, 03:23 PM
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United States, MO, Springfield
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issue with an RX pack is weight and space
A123/LiFe is heavy
iirc all spektrum RX can take a 2S lipo the issue there is can your servos
my 6HV has no room really for an RX pack with the Vbar on it
and standalone BEC weighs less any way
i put a buddys go pro on my 6HV and i could tell it flew different that helis wants to be a light as you can make it

now when i got a 700 ill run a 2S lipo or LiFe pack for sure since ill a lot more room and weight wont be an issue
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Old Nov 05, 2012, 03:31 PM
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Quote:
Originally Posted by Elios000 View Post
iirc all spektrum RX can take a 2S lipo the issue there is can your servos
It looks like the new ones can take it, but I'm not sure about the old ones. I have a lot of aircraft which have been flying for many years and I haven't changed the receivers. I'm using a lot of old AR6100s... even some so old they don't have QuickConnect.
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Old Nov 05, 2012, 03:55 PM
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right words

Quote:
Originally Posted by AndyKunz View Post
The correct term is "dynamic loading" for what you're talking about, not "aerodynamic drag."

That may help your google search come up with more meaningful hits.

Andy
thank you, master. so that is the correct term. i was trying to emphasize the fact that i mean the load on the surface (rudder or elevator for instance) due to the wind pressure on the surfaces, that becomes a load on the servo, and not the drag due to any load produced by friction in the linkage. got it?

now that you helped bringing the correct term, how about providing an answer to the question am posing?

that could be the help i expect.
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Old Nov 05, 2012, 03:59 PM
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All of em - up to 9.6v however the servos are all over the place in what voltages they can tolerate
I do have very good BEC regs -by Align - high amps and selectable volts - still The A123 (the real thing ) is my easy preferrence as they will recharge in a few minutes if needed and the big 2m pattern planes can use the 1100ma packs -plenty of current.
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Old Nov 05, 2012, 04:17 PM
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Quote:
Originally Posted by phil alvirez View Post
thank you, master. so that is the correct term. i was trying to emphasize the fact that i mean the load on the surface (rudder or elevator for instance) due to the wind pressure on the surfaces, that becomes a load on the servo, and not the drag due to any load produced by friction in the linkage. got it?

now that you helped bringing the correct term, how about providing an answer to the question am posing?

that could be the help i expect.
Actually, you were partly correct. Every time lift is produced, so is drag. Deflected control surfaces produce lift, just not always in the vertical direction, obviously. So, aerodynamic drag IS produced as an ever present byproduct and is definitely an overall component of servo loading, but it's not the only factor.
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Old Nov 05, 2012, 04:25 PM
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Phil,

I do my testing on the ground using an ammeter and a voltmeter to ensure good linkages. I use rules of thumb for torque and dimensional constraints for selecting servos. In flight I monitor the rx pack voltage.

I do not know of anybody who has a servo current telemetry system. Neat idea, but with 10+ servos in a plane it could get pretty overwhelming.

Another good term would be "flight loads" and if you check one of the aerodynamics forums (try www.rcgroups.com/modeling-science-136/ ) you should be able to find a tool to help derive some ballpark data. Every model aircraft is different, so an accurate number will not be found by computation.

Andy
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Old Nov 05, 2012, 05:10 PM
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Quote:
Originally Posted by phil alvirez View Post
i build systems that have almost no friction and all moves smoothy-i feel no drag with my fingers when i push or pull the linkage when disconnected from the servo.

my interest is regarding aerodynamic drag on the surface, particularly for rudder or elevator. i mean, when the plane is in flight and i send a signal to a surface and drag increases.
that's why i would like to learn if it could show a difference in readings of amps (or milliamps, whatever i could get).

or it just is asking too much to the system to show?

it all started when i was guessing how much aerodynamic drag is really applied to surfaces. i have the feeling that drag on rudder and elevator on a plane that is not flying at extreme conditions of aerobatics, like a sailplane thermalling, is practically nil, whilst flaps, spoilers or ailerons when applied hard could increase aerodynamic drag too much for the servo.
and am using 2 to 3 cells packs no larger that 1500mah that have a very flat discharge rate. in case this may have any effect.
DYNAMIC BALANCE OF CONTROL SURFACES
Patent 1937
http://www.google.co.uk/patents?hl=e...evator&f=false

More info.
http://www.homebuiltairplanes.com/fo...balancing.html

--------------------------

Servo Current Monitor for Eagletree Data Logger
http://www.eagletreesystems.com/micropower/serv.htm

These links may help.
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Old Nov 05, 2012, 05:14 PM
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no way

as i have the quanum telemetry system and the temp/amp meter too, i was thinking if it could be possible to connect the amps meter to 1 servo and see directly in the screen the increase of amps (or miliamps) when pushing a stick (let's say rudder) to the extreme and see the increase in amps. likewise with elevator. just to learn if am not forcing the servo beyond its limit.
the idea is to learn what size servo fits the specific surface without burning.
then connect it to another servo. and so on. 1 by 1. this way i could learn what size servo fits each surface.
i asked John and he told me that he doesn't think the quanum could do that.
here is his detailed answer:

i asked: is there a way to learn if a servo is being overloaded?
perhaps with the voltage telemetry transmitter Current & Heat Sensor?
am trying to see if with it i can measure the load, so i don't have to use a larger servo than necessary.
if when using that particular servo i can get readings that show the load, would be great.
i think i better explain that if possble, i want to get readings from the plane in flight when i send a signal to a servo and, if there is some aerodynamic drag on that surface, the amps increase and this reading can be seen at my screen.

his answer:

jj604
Phil you can, but not with the quanum I would think.
The problem with servo load is it is constantly changing and what you need is the peak value.
Eagletree make a servo current sensor for their system but it won't work with the Quanum. The Sensor is a precision Ammeter, with 0.01A resolution. It is capable of recording up to +/-10A burst current, but no more than +/-5A continuous current. It connects to your MicroPower eLogger, Seagull, or Data Recorder product to provide current/amperage measurement of Servos, or other low amperage devices.

The voltage and current readings that the Quanum provides isn't much help as the fluctuations in battery voltage and current will be very small due to servo loads. The resolution of the current sensor is about the same as the max current a reasonably big servo will ever draw.

The best simple solution was the Dimension Engineering Servosense

http://www.dimensionengineering.com/...ervosense-plus

Unfortunately they discontinued it and don't make them any more. You might find one for sale on the forums. They were about $15 new.

I have one and it works a treat.

John
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Old Nov 05, 2012, 05:31 PM
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in flight air pressure to servo

Quote:
Originally Posted by Reflex1 View Post
DYNAMIC BALANCE OF CONTROL SURFACES
Patent 1937
http://www.google.co.uk/patents?hl=e...evator&f=false

More info.
http://www.homebuiltairplanes.com/fo...balancing.html

--------------------------

Servo Current Monitor for Eagletree Data Logger
http://www.eagletreesystems.com/micropower/serv.htm

These links may help.
thank you for the exact links on dynamic balancing.
very interesting.

but my question is, by using telemetry, to be able to measure the load on a surface, due to pressure by the airflow (i called it aerodynamic drag) that is transmitted to the servo, at the moment i push the stick. see:
Originally Posted by phil alvirez
i build systems that have almost no friction and all moves smoothy-i feel no drag with my fingers when i push or pull the linkage when disconnected from the servo.
my interest is regarding aerodynamic drag on the surface, particularly for rudder or elevator. i mean, when the plane is in flight and i send a signal to a surface and the load (pressure to the servo) increases. how much? may it damage the servo?
that's why i would like to learn if it could show a difference in readings of amps (or milliamps, whatever i could get).
or it just is asking too much to the system to show?
it all started when i was guessing how much aerodynamic drag is really applied to surfaces. i have the feeling that drag on rudder and elevator on a plane that is not flying at extreme conditions of aerobatics, like a sailplane thermalling, is practically nil, whilst flaps, spoilers or ailerons when applied hard could increase aerodynamic drag too much for the servo.
and am using 2 to 3 cells packs no larger that 1500mah that have a very flat discharge rate. in case this may have any effect.
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Old Nov 05, 2012, 06:43 PM
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If you like to doodle with math, you can ballpark loads
- every servo today has a rating (maybe not accurate but there is one)
So-- do all the leverage (geometry) and see what ends up at the control surface . in ounces of thrust
Then - this is the good part - get some one who believes they can calculate the maximum load on the control surface -
good luck on that .- Most of the calcs I ve seen are just SWAGS
The reason being that we really have no set cruise speeds such as man carrying stuff has.
Best bet -
look at what works well in similar cases - and err on the safe side .
Then - measure aflight -
recharge packs and measure power consumed - This will give you CAPACITY but not peak loads
This is why I never skimp on battery or servos-
I have watched guys shift leverages to try and increase roll rates etc.,and end up with slower rolls - the servos were simply overloaded .
.
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Old Nov 05, 2012, 07:23 PM
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United States, MO, Springfield
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Quote:
Originally Posted by AndyKunz View Post
Phil,

I do my testing on the ground using an ammeter and a voltmeter to ensure good linkages. I use rules of thumb for torque and dimensional constraints for selecting servos. In flight I monitor the rx pack voltage.

I do not know of anybody who has a servo current telemetry system. Neat idea, but with 10+ servos in a plane it could get pretty overwhelming.

Another good term would be "flight loads" and if you check one of the aerodynamics forums (try www.rcgroups.com/modeling-science-136/ ) you should be able to find a tool to help derive some ballpark data. Every model aircraft is different, so an accurate number will not be found by computation.

Andy
hey Andy the Heli guys are really wanting flight pack telemetry that show mAh used in real time with an programmable alarm at set level used/left
just saying

as to amp usage for servo if you tied some thing inline off the RX pack/BEC you could see what the radio system as a whole is pulling again useful for helis
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Old Nov 06, 2012, 11:42 AM
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Quote:
Originally Posted by AndyKunz View Post
Phil,

I do my testing on the ground using an ammeter and a voltmeter to ensure good linkages. I use rules of thumb for torque and dimensional constraints for selecting servos. In flight I monitor the rx pack voltage.

I do not know of anybody who has a servo current telemetry system. Neat idea, but with 10+ servos in a plane it could get pretty overwhelming.

Another good term would be "flight loads" and if you check one of the aerodynamics forums (try www.rcgroups.com/modeling-science-136/ ) you should be able to find a tool to help derive some ballpark data. Every model aircraft is different, so an accurate number will not be found by computation.

Andy
Hitec will have a current monitoring solution specifically for servos - when it eventually comes out...
It will monitor 4 servos - I don't know what happens if you want to monitor more than that.

There of course is no reason why you couldn't use a standard current telemetry sensor (if the current reading has enough precision) for drive motors either and connect that in between the main receiver battery and servos.

Si.
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Old Nov 06, 2012, 12:05 PM
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Quote:
Originally Posted by richard hanson View Post
Electric models?
A seperate rx source for larger stuff to be sure However overvoltage with a reg is -my opinion not as good as direct power to rx.
On Spektrum- either direct 2 cell LiPo or best , direct power A123.
Regs are just one more failure point and large difference in voltage between source and output voltage creates BIG problems
This is why most ESC for over 6 LiPo will not have internal BEC output
I will be heeding your warnings on the Eneloop RX packs for my F3F glider, but I can't agree on separate switching BECs (NOT the linear BECs often included in ESCs) for two reasons:
  1. Real world experience tells me they are extremely reliable - I have mix of cheapo and expensive UBECs, but I've not not had one fail in any of my electric models (I don't ever use separate RX packs or the inbuilt ESC BEC, just a separate UBEC);
  2. Even if your Rx is ok at higher voltages many of the flat digital wing servos used in high performance gliders (Futaba 3150/3155, MKS 3125, KST 135MG etc) simply will not take the 7V of an unregulated LiFe - doing so invlidates the warranty, could cause premature failure and in some cases the servo will simply not operate at that voltage.
Based on this I think I'll risk the extra failure point of a LiFe pack with a UBEC thanks!
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Old Nov 06, 2012, 01:11 PM
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The LIFE is actually 6.6 volts -but a reg dropping from 7 volts to 5.5 or 6 is a very lightly loaded reg - I use my ALIGN reg for this -
It is when the BEC try to drop from much higher volts to 6 volts that they can get into possible trouble
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