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Ray Allen trim servos not working with Garmin autopilot servos

Mark33

Well Known Member
Hi gang. I have a question that I?m hoping someone can help me with.

I have a RayAllen 407 stick controller and trim servos. I also have Garmin autopilot servos.

Neither one of my trim servos are working. Do I also need a RayAllen ?servo relay decks? to get power to the trim servos or should the power passing through the Garmin autopilot servos be able to provide power (pass through) to the trim servos?

Thanks for the help.
 
Mark,
This was a bit of challenge for me when I retro-fit from old to G3X touch w/AP system. What I found was that the GSA 28 has to provide power to the Trim servo motor. From the deck power output /stick you would go to pin 11 and 12 on the GSA 28 connector, then pin 13 and 14 would go to the trim motor. At least that is how mine is setup. I had to cut the existing wires that came from the stick and at first had them wired up backwards. Also, if I remember correctly, don?t worry if you get them reversed because you can change directions or reverse the trim in the G3X settings ( might want to double check with Garmin).
 
Mark,
This was a bit of challenge for me when I retro-fit from old to G3X touch w/AP system. What I found was that the GSA 28 has to provide power to the Trim servo motor. From the deck power output /stick you would go to pin 11 and 12 on the GSA 28 connector, then pin 13 and 14 would go to the trim motor. At least that is how mine is setup. I had to cut the existing wires that came from the stick and at first had them wired up backwards. Also, if I remember correctly, don?t worry if you get them reversed because you can change directions or reverse the trim in the G3X settings ( might want to double check with Garmin).

Thanks for the reply! Yes, that?s exactly what I?m planning to do if I can?t get them to work without the relay decks. I was under the understanding that the relay decks weren?t needed....but it looks like they are.
 
This sounds like the problem I had on my plane. The GSA28 servo is PWM and the trim actuators are just analog voltage. When the AP is powered, the trim doesn't work. If you pull the CB on the AP, then its a straight pass through of the voltage.

I think Garmin changed the install manual subsequent to my problem to point to the special relay deck you need to get the PWM and Voltage mix to work. I think this is what I needed to make it work and it is a sole source part.

https://www.tcwtech.com/Installation instructions model st-1-12v-10a-bstr_rev1.1.pdf

You should only need this if the trim actuator needs more than 1 amp, which I think is all the AP can supply. Mine took up to 10A depending on the load applied.


Hi gang. I have a question that I’m hoping someone can help me with.

I have a RayAllen 407 stick controller and trim servos. I also have Garmin autopilot servos.

Neither one of my trim servos are working. Do I also need a RayAllen “servo relay decks” to get power to the trim servos or should the power passing through the Garmin autopilot servos be able to provide power (pass through) to the trim servos?

Thanks for the help.
 
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I also have a G407 Ray Allen grip. It is not designed to control the trim servo directly as it does not have SPDT switches ( for reversing) like some of the older models have. The G407 uses normally open switches with a common ground. Since there is no way to reverse the servo you need some type of relay. You also need relays if you are driving the trim with more than one grip.

I am using the Garmin GAD27 module which performs the relay function ,speed control, and has two sets of stick switch inputs. The output of this module is passed to the GSA28 autopilot servos. As mentioned by others when the GSA28 is off the trim voltage is passed directly through to the trim servo.

The purpose of the PWM is only to slow the speed of the trim servo. The servo can be driven at full speed with 12V or slower by reducing the PWM duty cycle - the servo does not care either way.

The GSA28 has a 1 amp limit for driving the trim servo, which should be sufficient for RV applications.
 
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Thanks for the reply! Yes, that’s exactly what I’m planning to do if I can’t get them to work without the relay decks. I was under the understanding that the relay decks weren’t needed....but it looks like they are.

relays are still needed. It's true that the 28 acts like a relay "when it is running!" If the power goes away, the 28 simply passes the signal/power directly through. In that case, a separate relay is needed to keep from fusing your little actuator switch shut. Most switches used are rated for something well less than an amp, and the servos can and often does draw a bit more than an amp.

Larry
 
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don’t worry if you get them reversed because you can change directions or reverse the trim in the G3X settings ( might want to double check with Garmin).

I don't think that is correct. From my recent installation experience, the G3X s/w will only allow you to
reverse the polarity/direction used by the auto trim function. You must get it right via wiring for trim activated by the trim input pins on the 28, which are typically fed by the trim switch. You set it up mechanically by getting it to work correctly from your trim switch and then use the configuration tool to make the s/w controlled, autotrim directions match it.

They do it this way, because it needs to work the same way when the power goes away and the internal relay closes.
 
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I don't think that is correct. From my recent installation experience, the G3X s/w will only allow you to
reverse the polarity/direction used by the auto trim function.

Interesting. I was having this exact conversation with Tim at Approach FastStack today and he indicated it is configurable.

PS, I sent a note asking G3Xpert to weigh in and clear up the conflicting information in this thread.
 
Update

I installed the relays....you need two; one for pitch and one for roll. Everything is working as it should now. I was able to go into the configuration mode in the G3x and switch direction of the trim motor inputs so that they moved in the direction I wanted them to.
Thanks everyone for your comments.
 
I am sure Justin from Garmin will be along shortly, but here is some more information in the meantime.

When the GSA 28 is powered down, the trim wires in and out of the servo are shorted together.

Test one, power down the autopilot. Does trim work? If it doesn't, you need to figure out why you don't have power/ground to the GSA 28 when you are trying to run trim. You cannot provide a discrete input to tell the servo to drive the trim, you must provide 12v and ground to the two trim inputs just as if the servo were not installed and you were wiring straight to the motor.
There is much talk about relays.

Relays are only needed if you have multiple inputs to the trim (pilot and copilot sticks) or if your switch is unable to switch power and ground. Some stick grips can do this, but some only give a discrete ground output when you try to drive the trim.

Test two, if trim runs, put power on the GSA 28 servos. With the autopilot not engaged, can you run trim?

Test three, in configuration mode, can you run the trim?

If you can run the trim in all three all cases, you now need to make sure it runs the correct direction in each case. This is actually a bit tricky as you can change servo directions in multiple places including in configuration mode. You many need to change it in wiring and in configuration to get everything to work properly. Remember, it needs to run the correct direction in all three test cases above.

Thanks
Levi
 
Interesting. I was having this exact conversation with Tim at Approach FastStack today and he indicated it is configurable.

PS, I sent a note asking G3Xpert to weigh in and clear up the conflicting information in this thread.

It is critical that the wiring from the switch to the trim servo is setup correctly, regardless of the s/w setting. When the power goes away on the gsa28, it closes a set of contacts to bypass itself. If you used the s/w to reverse the polarity, your switch will now work backwards from how it was working before. This is, I believe, why garmin doesn't provide a s/w option to change polarity. It would be dangerous.

Larry
 
Relays are only needed if you have multiple inputs to the trim (pilot and copilot sticks) or if your switch is unable to switch power and ground. Some stick grips can do this, but some only give a discrete ground output when you try to drive the trim.

This is only true if your switch has a current rating of at least 1+ amps. Most grip based switches are much less than this. The reason is that when the 28 is powered down, the full current for the trim motor is coming from the switch or relay. The relay is often needed for current carrying when the switch is not rated for the load.

Larry
 
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...or you could just use a GAD 27 for all the trim switch input/mixing (pilot/copilot) and servo control...
 
This is only true if your switch has a current rating of at least 1+ amps. Most grip based switches are much less than this. The reason is that when the 28 is powered down, the full current for the trim motor is coming from the switch or relay. The relay is often needed for current carrying when the switch is not rated for the load.

Larry

Yes, agreed. I was referring to older Ray Allen G305/307 grips, which can drive the servos directly. The G407 cannot because it cannot handle the current and it only has SPST switches for the trim buttons.
 
GSA 28 Trim Motor Wiring

Hi gang. I have a question that I?m hoping someone can help me with.

I have a RayAllen 407 stick controller and trim servos. I also have Garmin autopilot servos.

Neither one of my trim servos are working. Do I also need a RayAllen ?servo relay decks? to get power to the trim servos or should the power passing through the Garmin autopilot servos be able to provide power (pass through) to the trim servos?

Thanks for the help.

Hi Mark,

It will probably help to see a wiring diagram showing how you have the Ray Allen trim motors hooked up to the GSA 28 as well as the wiring from the switches to the GSA 28. Please send those over to [email protected] and we will take a look at them for you.

Thanks,

Justin
 
I don't think that is correct. From my recent installation experience, the G3X s/w will only allow you to
reverse the polarity/direction used by the auto trim function. You must get it right via wiring for trim activated by the trim input pins on the 28, which are typically fed by the trim switch. You set it up mechanically by getting it to work correctly from your trim switch and then use the configuration tool to make the s/w controlled, autotrim directions match it.

They do it this way, because it needs to work the same way when the power goes away and the internal relay closes.

Steve put together a good explanation of this in this post.

Here is a simplified version of the steps explained in the G3X Installation Manual to configure/test your trim installation.
  • Power off the servos.
  • Use aircraft trim switches to run the trim motor. If the trim motor runs in the wrong direction, swap the trim motor wires at the control stick, at the servo on pins 11,12 (switch inputs), at the servo on pins 13,14 (trim motor drive wires), or at the trim motor itself.
  • Verify that the trim now runs in the correct direction with the servos powered off.
  • Apply power to the servos.
  • Use the on screen controls on the servo configuration page to drive the trim motor for that servo.
  • If trim motor runs in the wrong direction, change the trim motor direction setting on that page from Normal to Reverse (or Reverse to Normal if it is presently Reversed).
  • Re-verify that the trim operates correctly in both the servo powered on and servo powered off conditions.

Thanks,

Justin
 
Steve put together a good explanation of this in this post.

Here is a simplified version of the steps explained in the G3X Installation Manual to configure/test your trim installation.
  • Power off the servos.
  • Use aircraft trim switches to run the trim motor. If the trim motor runs in the wrong direction, swap the trim motor wires at the control stick, at the servo on pins 11,12 (switch inputs), at the servo on pins 13,14 (trim motor drive wires), or at the trim motor itself.
  • Verify that the trim now runs in the correct direction with the servos powered off.
  • Apply power to the servos.
  • Use the on screen controls on the servo configuration page to drive the trim motor for that servo.
  • If trim motor runs in the wrong direction, change the trim motor direction setting on that page from Normal to Reverse (or Reverse to Normal if it is presently Reversed).
  • Re-verify that the trim operates correctly in both the servo powered on and servo powered off conditions.

Thanks,

Justin
I have set up my auto pilot with the trim motor control off and got the gain set ok. The only change I had to do was reverse the pitch motor control. The auto pilot works fine. I have turned on trim motor control I get trim up trim down signals on the PFD. If I move the trim switch the auto pilot disconnects.
In configuration if I turn on trim motor controls in LRU that would run gsa28 servos as trim motors instead of my ray allens the trim works with the auto pilot on. I know this is not the right way. But runs away in the wrong direction and a red trim warning is displayed. I run the trim through a GA27 and wired through the 28's trim works correctly both with and without power to the 28's. How do I set up the auto trim control?
 
I have set up my auto pilot with the trim motor control off and got the gain set ok. The only change I had to do was reverse the pitch motor control. The auto pilot works fine. I have turned on trim motor control I get trim up trim down signals on the PFD. If I move the trim switch the auto pilot disconnects.
In configuration if I turn on trim motor controls in LRU that would run gsa28 servos as trim motors instead of my ray allens the trim works with the auto pilot on. I know this is not the right way. But runs away in the wrong direction and a red trim warning is displayed. I run the trim through a GA27 and wired through the 28's trim works correctly both with and without power to the 28's. How do I set up the auto trim control?

In the config menu, there should be a setting for trim control direction. Options are normal or reverse. Try changing this for the axis that is trimming in the wrong direction while under AP control.

Larry
 
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