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Tundra10
Joined: 14 Jun 2010
Posts: 102
Location: Scarborough, Ontario
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 Posted: Thu Apr 16, 2015 7:28 pm Post subject: Dual Control Stick Trim Switches Without Relays |
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I see two restrictions to utilize this circuit:
The trim switches in your control stick would have to be not commonly
switched to ground. This might be a typical case, since it would half
the number of wires inside the control stick.
The trim switches would have to be capable of handling the trim motor
spikes. Unlike a relay, since the voltage polarity is reversed, the
usual diode protection for the switch could not be used. A
bi-directional device with a clamping voltage a little higher than bus
voltage might be desirable.
I think that is why the relay method is commonly used.
Jeff Page
Dream Aircraft Tundra #10
| Quote: | Time: 06:36:24 AM PST US
Subject: Dual Control Stick Trim Switches Without Relays
From: "user9253" <fransew(at)gmail.com>
Joel Graber designed and posted a circuit on VansAirforce that
controls a trim
servo motor using
Ray Allen G205 SPDT stick grip switches mounted on pilot and copilot
control sticks.
No relays are required. A PDF version can be download:
http://tinyurl.com/Trim-Circuit
Joel Graber has used this circuit in his RV-10 for over 600hrs.
In case of a runaway trim caused by a stuck switch or suicidal
copilot, the opposite
direction
button can be pressed and held until the fuse or breaker can be pulled.
I do not know if anyone else has thought of this wiring scheme before or not,
but I thought it both simple and ingenious. Even the Ray Allen
company thinks
that relays
must be used for 2 control sticks.
Joe
--------
Joe Gores
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user9253
Joined: 28 Mar 2008
Posts: 1920
Location: Riley TWP Michigan
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| Posted: Fri Apr 17, 2015 6:19 am Post subject: Re: Dual Control Stick Trim Switches Without Relays |
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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: | Quote: | | 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
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
Joe Gores |
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weasel
Joined: 15 Apr 2015
Posts: 1
Location: United States
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| Posted: Thu May 14, 2015 11:16 am Post subject: Re: Dual Control Stick Trim Switches Without Relays |
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| Tundra10 wrote: | I see two restrictions to utilize this circuit:
The trim switches in your control stick would have to be not commonly
switched to ground. This might be a typical case, since it would half
the number of wires inside the control stick.
The trim switches would have to be capable of handling the trim motor
spikes. Unlike a relay, since the voltage polarity is reversed, the
usual diode protection for the switch could not be used. A
bi-directional device with a clamping voltage a little higher than bus
voltage might be desirable.
I think that is why the relay method is commonly used.
Jeff Page
Dream Aircraft Tundra #10
| Quote: | Time: 06:36:24 AM PST US
Subject: Dual Control Stick Trim Switches Without Relays
From: "user9253" <fransew>
Joel Graber designed and posted a circuit on VansAirforce that
controls a trim
servo motor using
Ray Allen G205 SPDT stick grip switches mounted on pilot and copilot
control sticks.
No relays are required. A PDF version can be download:
http://tinyurl.com/Trim-Circuit
Joel Graber has used this circuit in his RV-10 for over 600hrs.
In case of a runaway trim caused by a stuck switch or suicidal
copilot, the opposite
direction
button can be pressed and held until the fuse or breaker can be pulled.
I do not know if anyone else has thought of this wiring scheme before or not,
but I thought it both simple and ingenious. Even the Ray Allen
company thinks
that relays
must be used for 2 control sticks.
Joe
--------
Joe Gores
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Just for data. I have been running this for well over 600hrs with no problems.
Joel
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
RV-10
RV-4 SOLD
Fisher Classic -- VW Power |
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