What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Garmin GSA28 with Ray Allen trim

von_flyer

Well Known Member
Advertiser
I would like to verify the wiring of the GSA28 elevator A/P servo also using a Ray Allen T3-12A trim servo. Here is what I have. In addition to verifying the connections perhaps someone can tell me if the hat switch on the stick pulls an input to ground to select that direction of trim servo movement? Notice I did not draw the Cooley Hat Switch yet on terminals 11 and 12. Thank you in advance.
 
Last edited:
This is my simplified drawing for my Garmin system. My system has a GAD 27.

Without the GAD 27 all your pin outs look correct when I compare them to my master drawing. Without a GAD 27, you will need a relay to have a second trim switch.
.
 

Attachments

  • TRIM-wiring.jpg
    TRIM-wiring.jpg
    86.1 KB · Views: 1,187
Last edited:
Thank you Michael. So the hat switch does take the signal to ground, true low. I don’t plan on a second trim switch so no GAD27.

I assume the GP1 input is configured in the G3X and displays the trim position.
 
Thank you Michael. So the hat switch does take the signal to ground, true low. I don’t plan on a second trim switch so no GAD27.

I assume the GP1 input is configured in the G3X and displays the trim position.

No, not grounded.

Without the 27, you need 2 relays to send power, in both polarities to the the servo. The RA servo consumes an amp and you hat switch cannot handle that. The 28 goes into bypass mode when shut down and your switches / relays need to handle the full amp in this case. Also, the motor reverses by getting power in different polarities. The 28 is also looking for different polarities, when not in bypass mode.

The relay is typically activated via a low/ground on the hat switch, assuming you feed + on the other side of the relay coils.
.
 
Last edited:
No, not grounded.

Without the 27, you need 2 relays to send power, in both polarities to the the servo. The RA servo consumes an amp and you hat switch cannot handle that. The 28 goes into bypass mode when shut down and your switches / relays need to handle the full amp in this case. Also, the motor reverses by getting power in different polarities. The 28 is also looking for different polarities, when not in bypass mode.

The relay is typically activated via a low/ground on the hat switch, assuming you feed + on the other side of the relay coils.
.

Are you saying 2 relays per trim axis, so a total of 4 relays for pitch and roll trim?
 
Trim motor wiring clarification

1. For pitch and roll trim, do I need 2 GAD27 units ?

Can someone supply a complete wiring diagram for Garmin 28 servos, Ray Allen trim servos and a single hat switch combination. Roll and pitch servos and wires coming from the autopilot controller are marked. Roll out #1, roll out #2, pitch out #1, and pitch out #2. No problem with the indicator wires. No relays installed and no GAD 27 yet. Cannot get trim hat switch to function when autopilot is turned off.
 
Trim Motor Control Wiring

1. For pitch and roll trim, do I need 2 GAD27 units ?

Can someone supply a complete wiring diagram for Garmin 28 servos, Ray Allen trim servos and a single hat switch combination. Roll and pitch servos and wires coming from the autopilot controller are marked. Roll out #1, roll out #2, pitch out #1, and pitch out #2. No problem with the indicator wires. No relays installed and no GAD 27 yet. Cannot get trim hat switch to function when autopilot is turned off.

John,

You only need 1 GAD 27. Page 27-15 of the G3X Touch Installation Manual shows the connection made from the switches, to the GAD 27, from the GAD 27 to the GSA 28, and then from the GSA 28 to the trim motor. Please let us know if you have any questions.

You can also reach us at [email protected]

Thanks,

Justin
 
If using a coolie hat type trim switch:

GAD 27 = no trim relays needed
No GAD 27 = trim relays needed (or similar trim servo controller function)
 
Why do I need a

Why do I need a GAD. 27 ? Just to get my GSA 28 to talk to my roll and pitch trim servos $499 is a big price to pay for a lot of un needed functions ?
 
Why do I need a GAD. 27 ? Just to get my GSA 28 to talk to my roll and pitch trim servos $499 is a big price to pay for a lot of un needed functions ?

You don't. The servo just passes through the trim power signals (when not auto-trimming). So, you just need a reversing relay deck if using a coolie-hat trim switch (single pole). Or, the RAC trim switch (DPDT center off)

(or, in my case, a solid-state H-bridge circuit made using these https://www.ebay.com/itm/DRV8871-dc-motor-driver-breakout-board-pwm-control-for-arduino/322593857204?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 with a carrier board to provide the logic level power supply and D-sub interface)
 
Last edited:
Ray Allen trim servos w/ GFC 500

With the G3X auto pilot off my Ray Allen trim servos operate normally with the 4 way hat on the pilot stick. I have a single toggle switch to power the Garmin GSA 28 servos and as soon as power comes on for the servos it pops the fuse for the trim servos. My system calls for a 1 amp fuse for both pitch and roll trim servos (same circuit). I have put a 4 amp fuse in place and it still immediately trips the fuse when the servos are powered up. I have a G3X with GFC 507 controller, new system not yet flown. RV-8A
 
working on mine as well just initial wire set up those don't pull hardly any power so you have something messed up lol sorry for the frustration post some pics of your connections
 
Here's a copy of my schematic pages that show the 2x GSA28s, GAD27, Ray Allen trim servos, and hat switch configuration. Works great in my plane.
 

Attachments

  • N430WB_SCHEMATIC_211222_trim.pdf
    187.9 KB · Views: 373
With the G3X auto pilot off my Ray Allen trim servos operate normally with the 4 way hat on the pilot stick. I have a single toggle switch to power the Garmin GSA 28 servos and as soon as power comes on for the servos it pops the fuse for the trim servos. My system calls for a 1 amp fuse for both pitch and roll trim servos (same circuit). I have put a 4 amp fuse in place and it still immediately trips the fuse when the servos are powered up. I have a G3X with GFC 507 controller, new system not yet flown. RV-8A

Resolved

Stupid, I had the "Garmin Reversing Adapters" plugged into the servos, between the servo and the wiring. These are only used when you have to unplug the servo for some reason and you need to use your trim manually. With the cable to the servo unplugged your trim won't work because it has to run through the servo so you plug in the Reversing Adapter so the trim works without the cable plugged into the servos
 
I had the "Garmin Reversing Adapters" plugged into the servos, between the servo and the wiring. These are only used when you have to unplug the servo for some reason and you need to use your trim manually. With the cable to the servo unplugged your trim won't work because it has to run through the servo so you plug in the Reversing Adapter so the trim works without the cable plugged into the servos

Glad you got this resolved. Just for posterity, this part is actually called the GSA 28 Removal Adapter - see section 18.5.2.5 in the current G3X installation manual (revision AP):

18.5.2.5 GSA 28 Removal Adapter

The GSA 28 connector kit is shipped with a GSA 28 removal adapter (011-03158-00). This part is not intended to be installed with the GSA 28, but is used to replace the GSA 28 when the harness connector is un-plugged. [...] The intention of this component is to allow operation of the CAN bus and trim motors when the servos are not plugged into the harness. It is recommended that a removal adapter is kept with each servo installation, in case the GSA 28 needs to be removed without losing functionality of the CAN bus and trim motors.
 
Thread resurrect.

With GAD 27 + GSA 28 + Ray Allen (RA) trim servos, two of the RA conductors will connect to the GSA 28. What are the other three RA conductors supposed to connect to? GEA 24? And should those three conductors be in shielded wire? And which (if any) of all these wires should not be bundled with others?
 
Last edited:
Thread resurrect.

With GAD 27 + GSA 28 + Ray Allen (RA) trim servos, two of the RA conductors will connect to the GSA 28. What are the other three RA conductors supposed to connect to? GEA 24? And should those three conductors be in shielded wire? And which (if any) of all these wires should not be bundled with others?

Yes, those 3 wires from the RA trim go directly to the GEA 24 and yes they are shielded. Mine are 3-22 cable and all three are together surrounded by the shield.

See post #2 with my drawing. This simplified drawing DOES NOT show the shielding.
 
Back
Top