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Servos jumping on power-up

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Old 12-08-2012, 02:31 PM
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Default Servos jumping on power-up

I've tried searching without much luck. As the title says, when I power up most of my planes (6.0-6.6V) and already have the SD-10G on (FHSS-1 mode on all), the servos "jump" for a fraction of a second. Some move to rather large extremes, some not so much, some hardly at all. All servos are analog - the cheaper and older ones exhibit the most movement. This would be very bad on a power dip while flying. Also, it looks like some could overtravel the limits of the surface's movement.
Is this an issue with high frame rate, or can I work around it?
Love the SD-10G !!!
Thanks for the help,
Jim
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Old 12-08-2012, 02:51 PM
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Default RE: Servos jumping on power-up



Sounds very like a 2.4 set that has not been re-bound to the reciever after initial set-up ?

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Old 12-08-2012, 03:06 PM
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Default RE: Servos jumping on power-up

John,
Hmmm - could be that. I'll try a re-bind in the AM. I've never had to re-bind any of my 10 ATX Rx's, though. Puzzling. I'll report back tomorrow.
Thanks for the tip!
Jim
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Old 12-08-2012, 03:26 PM
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Default RE: Servos jumping on power-up


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ORIGINAL: SRQFlyer

John,
Hmmm - could be that. I'll try a re-bind in the AM. I've never had to re-bind any of my 10 ATX Rx's, though. Puzzling. I'll report back tomorrow.
Thanks for the tip!
Jim
Hi jim, it's usually the servo reverse function that's the culprate, is it possible in your other set-up's that you didnt have to use that function of the TX ?
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Old 12-09-2012, 09:26 AM
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Default RE: Servos jumping on power-up

John,

ALL my Airtronics setups "jump" somewhat when the power is first applied. Re-binding this new setup did not make any difference at all. This one is especially bad with the Bluebird servos - they go about 150% in one direction. Real bad news is that direction is DOWN elevator!

I'm going to set this plane up using one of my Futaba systems (which do not do this) instead and wait for an answer from Mr. Greene. Also, I'll get some digital servos to try.

Thanks for your answers,
Jim
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Old 12-09-2012, 09:46 AM
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Default RE: Servos jumping on power-up

Hi jim, can you swap around the servos, one that doesnt do much and the one that gives you all that down elevator. That will tell you whether it servo specific or it's down to the TX/RX ?

Just the plugs in the reciever and not the actuall servos themselfs ?
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Old 12-09-2012, 10:01 AM
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Default RE: Servos jumping on power-up

OK, I'll throw a wrench in the trouble shooting servo jump.

First, nearly all my Airtronic rigs have some minor degree of jump. I've come to recognise it as a good power up. Servo jump moments after a turn on the rx usually meant low battery.

Now, with this discussion I went out in the build room where I'm re-radioing my old trusty Fleet model 10. I've two Airtronics 322 servos on a walking beam driving the elevator. New SD8000 with new 6 VDC batts. Both servos are Y corded to the elevator channel.

Turning on tx then rx and only one of the two elevator servos jump. Down is the preferred and did note that it jumps until the blue light on the rx comes on then assumes it's proper position. Occured each time I lit 'er up and it didn't matte if I used a 6vdc or 4.8 vdc battery.

Soooo....??

Ray W.
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Old 12-09-2012, 10:13 AM
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ORIGINAL: Kinner

OK, I'll throw a wrench in the trouble shooting servo jump.

First, nearly all my Airtronic rigs have some minor degree of jump. I've come to recognise it as a good power up. Servo jump moments after a turn on the rx usually meant low battery.

Now, with this discussion I went out in the build room where I'm re-radioing my old trusty Fleet model 10. I've two Airtronics 322 servos on a walking beam driving the elevator. New SD8000 with new 6 VDC batts. Both servos are Y corded to the elevator channel.

Turning on tx then rx and only one of the two elevator servos jump. Down is the preferred and did note that it jumps until the blue light on the rx comes on then assumes it's proper position. Occured each time I lit 'er up and it didn't matte if I used a 6vdc or 4.8 vdc battery.

Soooo....??

Ray W.
Interesting you mention the Y lead, is it an older amplified Y lead ? if your on 2.4 they say not to use them as they can cause erratic servo function, they were developed in the days of pcm to boost the signal ? If using 2.4 system then use non amplified Y leads.
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Old 12-09-2012, 10:51 AM
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Default RE: Servos jumping on power-up

All brand new out of the Airtronics packages. Un amplified as far as I know.



Now, it gets interesting.. I swapped the servos going into the Y cord. On start up, BOTH servos jumped and return to neutral when the binding lite came on steady. Swaped the servos back and only the one single servo jumps while the other stays put.

Love it..

Ray W.
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Old 12-09-2012, 11:10 AM
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Default RE: Servos jumping on power-up

Maybe just one of the 'quirks' of that radio.
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Old 12-09-2012, 12:22 PM
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Default RE: Servos jumping on power-up

In my setup(s) - no Y-cords at all. All channels "jump" and swapping servos around doesn't make any difference. I've bench-tested most of my (150+) servos and the Bluebirds and HK ones are terrible. They overtravel the normal endpoint by 50% or more for a brief time (until the blue light comes on). Hitecs only seem to move a little. Older Futabas are in between, but not bad.

I think it is an issue of the servo getting +/- voltage, but no signal for a brief time. The Airtronics seems to take several tenths of a second to "boot up". When I do the same test with either of my Futaba 2.4 systems, the Rx is on line much faster and the servos don't have a chance to get "confused" and move. Just my thoughts.

Let's see what Mr. Greene has to say.

Jim
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Old 12-10-2012, 08:37 PM
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Default RE: Servos jumping on power-up

Oops - I'm embarrassed! I referred to Mike Greenshields as Mr. Greene. Bad case of CRS, but to be expected at my age.

Anyway, I think my analysis of power to the servo before it gets a signal is the culprit. With further testing, I was able to duplicate the motion of the servos with an older 607 Futaba Rx that boots up slowly. Most servos are OK and only move a little, but the cheapies can move a whole bunch!

Conclusion (for me) is that with FHSS-1 Airtronics Rx's, one should use decent servos or digitals. Of course FHSS-3 Rx's need digitals.

Thanks to all who offered ideas.

JIm
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Old 12-10-2012, 10:32 PM
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Hi jim, that's good news that you have a plausable explanation, nothing worse than not knowing whats going on !

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