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HelicopterRadio - Servo - Gyro - Gov - Batt › GY520 initialisation problem
10-19-2009 08:29 PM  8 years agoPost 1
MattHarper

rrApprentice

Lancashire, UK

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I've been chatting to a guy at the club who is experiencing strange behaviour, at power up, with a newly installed GY520. I'm only familiar with JR and CSM gyros and can't really comment on what he's seeing so would appreciate some ideas. At power up, with the DSX9 transmitter powered up first, the 8700G servo drives to one extreme of travel, beyond the limits programmed in to the gyro, and then after the GY520 has intialised, it drives back and forth between the programmed end points as per the manual. I'm concerned that this initial extreme movemement will pop a link or worse. My initial thoughts are that during the period when the DSM2 link is established, the receiver output is indeterminate and causes the gyro to do its own thing. Is this normal for a GY520? Ideas?

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10-19-2009 08:41 PM  8 years agoPost 2
BarracudaHockey

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Jacksonville FL

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I dont know if its good for it or not, personally I doubt it, but its not unusual for those servos to do that with Futaba gyros during boot up.

Andy
AMA 77227
http://www.jaxrc.com

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10-19-2009 08:52 PM  8 years agoPost 3
MattHarper

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Lancashire, UK

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I hope not, if you are right, then it's a fundamental design fault. In the absence of a receiver signal, the uncommanded servo movement should be limited to somewhere between the programmed end points. I guess that's why thinking men fly JR

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10-20-2009 01:27 AM  8 years agoPost 4
ssmith512

rrKey Veteran

Indianapolis, IN USA

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Futaba 12FG
GY520 w/ BLS251

My setup does not do what you describe at all. Servo never moves at power up until gyro initializes, and then it doesnt even travel to the set end points, just a quick blip in both directions, back to center, and done.

Steve

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10-20-2009 08:00 PM  8 years agoPost 5
Foz

rrApprentice

Earth

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Does he have the right servo type selected in the gyro? I accidentally had digital selected with an analog servo and the servo went all the way to the end of its travel like you described. That should not happen if set up properly.

Foz

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10-21-2009 01:07 PM  8 years agoPost 6
MattHarper

rrApprentice

Lancashire, UK

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The servo type is programmed as analogue in the Gyro. The servo is a JR8700G. Looking at this discussion

http://www.helifreak.com/showthread.php?t=142997&page=2

it appears that others are seeing the same thing. I really don't understand what is causing this problem. I've totally run out of ideas

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10-21-2009 03:45 PM  8 years agoPost 7
Foz

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Earth

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It looks like the other person with problems was using the same servo. Maybe it just doesn't like the 8700? Are you sure that the end point settings took? It won't accept them if there is not enough travel in one direction.

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10-22-2009 09:23 PM  8 years agoPost 8
MattHarper

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Lancashire, UK

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Well, I've just had word that with an Align DS610, everything is perfect. No extreme travel at power up, it just behaves as per the manual. Very curious, why should the 8700G exhibit such movement ?
Could it be down to the gyro's frame rate or the servo's dead band ? Any ideas

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10-23-2009 07:52 PM  8 years agoPost 9
RAK402

rrElite Veteran

Alhambra, CA

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I have nine GY520's flying right now and one spare (destined for my Knight Pro). The driving behaviour that you describe is not normal at all.

I have had the very thing you describe occur with a GY520 and a JR 3500G.

I put about 30 flights on a Trex 450 Pro then, one morning when I connected the battery, the servo drove all the way to one end (past the stops programmed into the gyro), and went back and forth, past the stops.

I thought it might have been the gyro.

I swapped both the gyro and the servo several times (so that the results of the tests would be repeatable).

The servo was at fault, not the gyro. I believe that the amp is blown in the servo.

Upon boot up, the gyro should cause the servo to move back and forth, twice, but not beyond the programmed amount of travel.

The same gyro is working fine, by the way, with a new JR 3500G.

Team KBDD/Compass Team Manger/Experience RC/Team JR Americas/WR Field Rep

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HelicopterRadio - Servo - Gyro - Gov - Batt › GY520 initialisation problem
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