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Multiplex Evo with Gy401 gyro

Old 05-30-2010, 05:12 PM
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Default Multiplex Evo with Gy401 gyro


I switched one of my helis over to my Evo 9 radio from a Spektrum DX6i, and noticed that all the center positions for the servos changed. While that was easily rectified by moving the control horn for physical surfaces, it's been playing a bit of havoc with setting up a GY401 gyro. The instructions I've been following say to center the rudder servo before connecting the gyro, then using the gyro's end-point pot to adjust the range. However, the gyro has a different idea of what center should be and offsets the tail servo by about 30 degrees. The only way I've found to cancel this out is to use the "calibrate" menu and offset the center point by 25%. Once I do that, the gyro seems "happy". It centers where I want it to, and has equal throw both directions.

All channels are set for UNI signaling, which should be ~1.5ms for the center position vs 1.6ms for the MPX. If the servos are expecting 1.5ms for the center, why is there such a big change in center position? Please note, the only thing I changed was the TX that was bound to the RX.

Here's the technical details of my setup:
TX: Evo 9 v2.62 with spektrum module (not a hacked unit, the one actually designed for this radio)
RX: Spektrum 6100e
Servos: Futaba S3153 & S9254, Spektrum DSP75, Graupner DES-477 (all digital capable)
All channels set for UNI signaling.

Any idea why the center point changes so much, and why the GY401 would think the center point was so far off? Just for kicks, I set the channel to MPX mode, and it appeared to require less of an off-set to set the same center point for the tail servo through the gyro.


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