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Old May 02, 2014, 01:48 PM
...one of my nicer landings
United States, WA, Walla Walla
Joined Mar 2014
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Linear+CC switching BEC vs ESC w Switching BEC

http://www.rcgroups.com/forums/showthread.php?t=2158536

"...Who uses linear BEC's without a backup switching BEC on a plane with digital servos, and why?

Secondly, what advantages are for linear vs switching? Sounds to me like switching BEC's run cooler and are more reliable with digital servos. Why linear BEC's?

Thank you"
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Old May 02, 2014, 06:22 PM
...one of my nicer landings
United States, WA, Walla Walla
Joined Mar 2014
232 Posts
Quote:
Originally Posted by suddenstop View Post
http://www.rcgroups.com/forums/showthread.php?t=2158536

"...Who uses linear BEC's without a backup switching BEC on a plane with digital servos, and why?

Secondly, what advantages are for linear vs switching? Sounds to me like switching BEC's run cooler and are more reliable with digital servos. Why linear BEC's?

Thank you"
Curtis Suter provided the site below in a different forum. Interestingly, the rc calc page had some easy calcs for prop-motor combos

http://www.radiocontrolinfo.com/RCca...Calculator.php

http://www.radiocontrolinfo.com/radio/bec.php
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Old May 02, 2014, 11:02 PM
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As I understand a switching BEC, uses FETs "switching" on and off to regulate voltage to your receiver/servos. So less or minimal heat is generated as compared to a linear BEC.

A linear BEC dissipates heat to drop the LiPo voltage to nominal 5 Volts. As the BEC is usually built into the ESC, heat from the linear BEC can also cause the ESC to overheat and fail.
As Don does (in the other thread )
http://www.rcgroups.com/forums/showp...82&postcount=5
I have decided to use the internal switching BEC in my Castle Ice LIte ESC as a power source for my Rx and Servos in my E-sailplanes. These are switching BECs with a 5 amp output. That way, I only have one battery source to carefully monitor. Like Don, I replace my LiPo after each flight, and monitor how many mAH I need to put back into a LiPo after each flight. I only use high quality Thunder Power LiPos, and I charge them at a slow 1C charge rate. By carefully monitoring motor run time, I generally only run the LiPo down to 50% capacity .
I also have the throttle switch on my Tx setup with a timer display. So I always have a cumulative readout of how many seconds I have run the motor.
When I fly this Xplorer 3.8 M with 6 digi servos, I have only a small 3S-1800-70C LiPo. I need to carefully monitor motor run time!
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Last edited by 320pilot; May 02, 2014 at 11:16 PM.
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Old May 02, 2014, 11:16 PM
...one of my nicer landings
United States, WA, Walla Walla
Joined Mar 2014
232 Posts
Quote:
Originally Posted by 320pilot View Post
As I understand a switching BEC, uses FETs "switching" on and off to regulate voltage to your receiver/servos. So less or minimal heat is generated as compared to a linear BEC.

A linear BEC dissipates heat to drop the LiPo voltage to nominal 5 Volts. As the BEC is usually built into the ESC, heat from the linear BEC can also cause the ESC to overheat and fail.
As Don does (in the other thread )
http://www.rcgroups.com/forums/showp...82&postcount=5
I have decided to use the internal switching BEC in my Castle Ice LIte ESC as a power source for my Rx and Servos in my E-sailplanes. These are switching BECs with a 5 amp output. That way, I only have one battery source to carefully monitor. Like Don, I replace my LiPo after each flight, and monitor how many mAH I need to put back into a LiPo after each flight. I only use high quality Thunder Power LiPos, and I charge them at a slow 1C charge rate
I also have the throttle switch on my Tx setup with a timer display. So I always have a cumulative readout of how many seconds I have run the motor.
When I fly this Xplorer 3.8 M with 6 digi servos, I have only a small 3S-1800-70C LiPo. I need to carefully monitor motor run time!
Thanks for the great explanation. BTW, A320? ... and your Explorer is droolworthy.

Makes a ton of sense to me. Being a noob I was sold, or bought depending on outlook, way too much. You also brought up a great idea. I can program the timer on a switch that starts and stops with the motor switch. Sure would be a more accurate way to know what you can and probably shouldn't do. Thank you!
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Last edited by suddenstop; May 02, 2014 at 11:19 PM. Reason: needed it
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Old May 02, 2014, 11:17 PM
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I corrected my text a bit.. above. Yes I did fly Airbus 320/319/321 for about 10 years as a Captain.
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Old May 02, 2014, 11:41 PM
...one of my nicer landings
United States, WA, Walla Walla
Joined Mar 2014
232 Posts
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Originally Posted by 320pilot View Post
I corrected my text a bit.. above. Yes I did fly Airbus 320/319/321 for about 10 years as a Captain.
Boeing and NASA family. Just curious, from your experience flying Airbus, do you try to automate as much as possible in your sailplanes (multiple preset flight modes) or do you prefer one basic flight mode that you manipulate depending on the changing conditions or needs?
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Old May 03, 2014, 11:02 PM
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Well, I haven't had a chance to compete with other pilots, living in Northern Vermont. I just set up a chair, and see how long I can stay in the air, without motor re-starts. For the floaty ones, Pulsars, Xplorer I just have a reflex mode , then a "camber" mode when I look for lift. I can get them quite high, say above 3000 AGL, I need a control input to get them down safely , with a high sink rate common to all types.
Because I fly many different types, I try and "standardize" controls between my different E-sailplanes, warmliners, etc with throttle on a switch, and left stick for flaps. No extra switches/sliders to have to play with..Flaps are mixed to elevator so even if I can barely see the bird, I can gradually extend full flap without a stall; the nose pitches down.
The aircraft with ailerons are setup so as I select through about 2/3 flaps the ailerons start to automatically rise up as "crow". This gives me less pitch up as I extend maximum flaps and allows me to modulate flaps/crow as necessary with out running out of elevator travel.
All on the left stick. Keep it simple!
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Last edited by 320pilot; May 03, 2014 at 11:24 PM.
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Old May 04, 2014, 10:36 AM
...one of my nicer landings
United States, WA, Walla Walla
Joined Mar 2014
232 Posts
Quote:
Originally Posted by 320pilot View Post
Well, I haven't had a chance to compete with other pilots, living in Northern Vermont. I just set up a chair, and see how long I can stay in the air, without motor re-starts. For the floaty ones, Pulsars, Xplorer I just have a reflex mode , then a "camber" mode when I look for lift. I can get them quite high, say above 3000 AGL, I need a control input to get them down safely , with a high sink rate common to all types.
Because I fly many different types, I try and "standardize" controls between my different E-sailplanes, warmliners, etc with throttle on a switch, and left stick for flaps. No extra switches/sliders to have to play with..Flaps are mixed to elevator so even if I can barely see the bird, I can gradually extend full flap without a stall; the nose pitches down.
The aircraft with ailerons are setup so as I select through about 2/3 flaps the ailerons start to automatically rise up as "crow". This gives me less pitch up as I extend maximum flaps and allows me to modulate flaps/crow as necessary with out running out of elevator travel.
All on the left stick. Keep it simple!
You have some really nice looking planes 320. Thanks for sharing and thanks for the ideas about set up. Over an hour from 'free' energy. Awesome. I look forward to ten minutes

Being a noob, I initially programmed a FH Raptor with the throttle on a slider so I could have flaps transitioning into crow on the left stick ... as you have. I was convinced "proper" mode 2 had throttle on the left stick and re-programmed it that way still leaving flaps, etc. on left stick. Throttle is going on the spring switch now. Off or on, with off being the default. Camber was on a slider though the left stick gave it too.

This first setup basically gave me camber control and elevation on the left stick and roll on the right stick. I think that changing it, at least in part, probably led to my first dramatic 'suddenstop'.

As I unintentionally explored the fringes of the flight envelope, sheesh, I inadvertently increased throttle in my confusion. With things getting faster and out of control, and too focused on recovery to notice a running motor, entered and spun in from I think an accelerated stall. I didn't particularly like the plane at that point anyway ... but still.

What I didn't do was mix elevator to flaps or flaps to aileron, etc. Lift increases with flaps and to compensate, a little down elevator makes sense. I suppose a little up elevator may help slow things with crow. Or, the lifting wing in an aileron roll rises quicker than the lowering wing drops, I think, leading to yaw... adverse or otherwise. I should have remembered from my 15 hours or so in a Cessna 152. Every pitch or power change requires a trim change. RIght? I need to get my books out.


I like your idea of a single, duplicated setup over a fleet of airplanes. I do appreciate the help and ideas. All this work to keep it simple requires complication.
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Last edited by suddenstop; May 04, 2014 at 10:40 AM. Reason: ATC
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