nuckolls.bob(at)aeroelect
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 Posted: Sat Nov 23, 2013 9:11 am Post subject: Garmin G3X Autopliot Auto Trim with Big Trim Motor |
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So finally, my question: Can we use FETs, an H Bridge (which i don't
fully understand) or something else to amplify the current
proportionally to the PWM signal?
You've identified the fact that your "current boost"
methodology needs to be solid-state fast. Relays
won't cut it.
I should add, we have two sticks, each with trim control. The legacy
system that is in there has Bosch type relays that control the trim.
Figure C-1.6 suggests that manual trim commands
are simply looped through the GX3 hardware when
the autopilot is disengaged.
I am including a schematic for a possible recommendation from
Garmin. The caveat to this installation is that it seems we would
have to run the trim at full speed all the time.
Yes, you can craft an h-bridge amplifier to boost
the G3X output to drive the trim motor. It appears
that GS28 servos from Garmin have built in run-time
limiting features. I suspect that no such feature
is offered internal to the G3X.
The h-brige buffer is not a big deal, probably less
than $10 worth of parts. But such a device puts
major silicon downstream of the G3x in a manner
that no existing run-time limiting can control.
How handy are you with a soldering iron and would
you want to consider building a run-time-limited
buffer amplifier from scratch?
Bob . . .
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