Today's Message Index:
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1. 07:20 AM - Re: Dual Control Stick Trim Switches Without Relays (user9253)
2. 02:51 PM - Re: Re: Dual Control Stick Trim Switches Without Relays (Robert L. Nuckolls, III)
3. 04:16 PM - Re: Dual Control Stick Trim Switches Without Relays (user9253)
Message 1
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| Subject: | Re: Dual Control Stick Trim Switches Without Relays |
The pilot's trim switches require 4 wires, the copilot's 5.
Ray Allen documentation includes includes wring diagrams for installation without
using relays. See WIRING SCHEMATIC FOR STYLE 1
http://www.rayallencompany.com/RACmedia/instructionsG2grip.pdf
Quote from Ray Allen's pdf:
> The single pole double throw switches in the G205 stick grip are each rated for
5 amps, so they can be wired directly to your Ray Allen servos.
I could not find any mention of arc suppression in Ray Allen's documentation.
Either arc suppression is built into their servos or else the motor current is
small enough that they are not concerned with inductive voltage spikes. I know
that the elevator trim servo in my RV-12 can be operated with a 9 volt transistor
radio battery (for testing purposes). The pitch trim circuit, designed
by Van's Aircraft in the RV-12, does not include arc suppression or relays.
I think that Joel Graber's trim switch circuit is great.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=440948#440948
Message 2
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| Subject: | Re: Dual Control Stick Trim Switches Without |
Relays
At 09:19 2015-04-17, you wrote:
>
>The pilot's trim switches require 4 wires, the copilot's 5.
>Ray Allen documentation includes includes wring diagrams for
>installation without using relays. See WIRING SCHEMATIC FOR STYLE 1
>http://www.rayallencompany.com/RACmedia/instructionsG2grip.pdf
>Quote from Ray Allen's pdf:
> > The single pole double throw switches in the G205 stick grip are
> each rated for 5 amps, so they can be wired directly to your Ray Allen servos.
> I could not find any mention of arc suppression in Ray Allen's
> documentation. Either arc suppression is built into their servos
> or else the motor current is small enough that they are not
> concerned with inductive voltage spikes. I know that the elevator
> trim servo in my RV-12 can be operated with a 9 volt transistor
> radio battery (for testing purposes). The pitch trim circuit,
> designed by Van's Aircraft in the RV-12, does not include arc
> suppression or relays.
When driving a PM motor (i.e. the Ray-Allen actuators
or similar), no arc suppression is necessary . . .
for a couple of reasons. The first is that the
inductive component of these little motors (or
any PM motor) is small compared to that of say
a relay of the same voltage and current demand.
Secondly, the effective voltage impressed across that
inductance is a small fraction of applied (i.e.
bus) voltage. This is because the rotating armature
generates a counter emf component that opposes the
applied voltage.
For example, If you know the motor's resistance
. . . let's say 28 ohms and that it draws say 100
milliamps under full load with 14 volts applied
we can deduce the following:
0.1 amps x 28 ohms equals 2.8 volts. This means
that counter emf generated by the rotating windings
is 14 - 2.8 or 11.2 volts. While rated at 14 volts
in this particular service the motor actually RUNS on
2.8 volts!
If you study the opening circuit voltage across a
spreading set of contacts controlling a PM motor,
you will find it to be VERY UNLIKE that which
occurs across the battery master switch.
The energy in an inductor is proportional to
L x I(squared). Given that the value of current
for the trim motor is on the order of 100 mA vs.
say 700 mA for the battery contactor, all other
things being equal (inductance), then the energy
released to arc the contacts will be 7 squared or
about 1/50th smaller for the motor than for a
battery contactor. Now stack the ratio of inductances
on top of the analysis and the energy gets small still
by perhaps another factor of 10.
Ergo, one can expect satisfactory service life
from the Lilliputian switches controlling a
motor that wants to be a hydraulic pump driver
when it grows up.
Bob . . .
Message 3
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| Subject: | Re: Dual Control Stick Trim Switches Without Relays |
Thanks for that information Bob. Very interesting.
Joe
Do not archive
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=440958#440958
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