Today's Message Index:
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1. 05:51 AM - Re: PWM ELEVATOR TRIM SERVO SPEED CONTROL (Robert L. Nuckolls, III)
2. 06:46 AM - Re: ground power deep discharge of battery (user9253)
3. 07:12 AM - Re: PWM ELEVATOR TRIM SERVO SPEED CONTROL (user9253)
4. 07:21 AM - Schematics (Neal George)
5. 08:48 AM - Re: Schematics (Bob Verwey)
6. 10:10 AM - Re: Re: ground power deep discharge of battery (Robert L. Nuckolls, III)
7. 10:11 AM - Re: Re: PWM ELEVATOR TRIM SERVO SPEED CONTROL (Robert L. Nuckolls, III)
8. 06:25 PM - Re: Schematics (user9253)
Message 1
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| Subject: | Re: PWM ELEVATOR TRIM SERVO SPEED CONTROL |
> ACTIVE voltage regulators incorporated as
> suggested in the drawing are CONSTANT
> VOLTAGE sources irrespective of load.
> Motors do not automatically 'draw more
> current' as their driving voltage is reduced.
> Using a series resistor to control speed
> makes speed regulation so poor that it SEEMS
> as if motor current is being modulated with
> speed . . . not so.
I've had some direct questions on this
topic . . . perhaps I went too far into
the weeds with the physics and offered
insufficient practical approach to
individual solutions.
If anyone is having trouble managing
their trim system performance, please
have them join us here on the List or
drop me a line personally. I've
worked trim systems on everything from
C182 to Hawker 4000 and most of those
in between. There ARE proven solutions
but they may require tailoring to a
builder's specific situation.
It CAN be fixed.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 2
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| Subject: | Re: ground power deep discharge of battery |
With my circuit, both the master switch must be on and the momentary switch pushed
in order to energize the ground power contactor.
Installing an indicator light would be easier, but the light could be overlooked.
Regardless, a fuse should be installed in series with the contactor coil to protect
against reverse polarity.
There is a 50-50 chance of the ground power battery being connected backwards.
If the polarity is backwards, the diode that is across the contactor coil will
conduct a large current and blow the fuse that you are going to install.
Hopefully that will happen quick enough to prevent damage to expensive avionics.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=505967#505967
Message 3
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| Subject: | Re: PWM ELEVATOR TRIM SERVO SPEED CONTROL |
Bob, thanks for the information. If I ever redesign my trim circuit, it will contain
a LM317.
You asked about the RV-12 trim circuit. Attached is a schematic of the original
trim circuit.
Van's has completely changed it in later models. But they still use PWM.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=505968#505968
Attachments:
http://forums.matronics.com//files/trim_speed_738.png
Message 4
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Gentlemen =93
I would like recommendations for a low-cost schematic drawing utility for s
omeone who doesn=99t speak CAD...
Neal George
Message 5
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NANOCAD freeware
On Thu, 10 Feb 2022, 17:26 Neal George, <neal.george@gmail.com> wrote:
> Gentlemen =93
>
> I would like recommendations for a low-cost schematic drawing utility for
> someone who doesn=99t speak CAD...
>
>
> Neal George
>
Message 6
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| Subject: | Re: ground power deep discharge of battery |
>If the polarity is backwards, the diode that is across the contactor
>coil will conduct a large current and blow the fuse that you are
>going to install.
>Hopefully that will happen quick enough to prevent damage to
>expensive avionics.
Nothing 'hopeful' about it. The diode, being FORWARD
biased, will not have a voltage drop not exceeding
1 volt or so while the fuse is in the process of
melting it's brains out . . . a couple milliseconds.
The voltage impressed on the contactor coil during
this interval is too short and too low for the
contactor to even think about closing.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 7
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| Subject: | Re: PWM ELEVATOR TRIM SERVO SPEED CONTROL |
At 09:11 AM 2/10/2022, you wrote:
>
>Bob, thanks for the information. If I ever redesign my trim
>circuit, it will contain a LM317.
>You asked about the RV-12 trim circuit. Attached is a schematic of
>the original trim circuit.
>Van's has completely changed it in later models. But they still use PWM.
PWM is much better than a simple series resistor but
still far short of optimal performance possible
with fewer components.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 8
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I use ExpressPCB Classic.
https://www.expresspcb.com/expresspcb-classic-pcb-layout-software/#wow-modal-id-1
The program is free and easy to learn. I used it to draw the schematics attached
to my recent posts.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=505983#505983
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