[NSRCA-discussion] Analog Servo RF Masking and....Thanks!
John Pavlick
jpavlick at idseng.com
Thu Jul 6 16:57:47 AKDT 2006
Scott,
That's why I asked if you had an oscilloscope. You may have been able to see
the screwed up servo pulses with that. Anyway, at this point, don't worry
about this stuff. Go out and practice! That's the most important thing right
now. See you at the NATs.
John Pavlick
http://www.idseng.com
BTW - I flew digital servos on a Futaba PPM Rx last year. No problems. You
have something going on there - re-visit it when you get back from the NATs.
-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Scott Pavlock
Sent: Thursday, July 06, 2006 1:08 AM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Analog Servo RF Masking and....Thanks!
Jim,
Your post makes more sense to me than any other so far. This would explain
why so many different set ups revealed the same jittery results, but when a
PCM receiver was introduced, it relieved the problem.
I am happy to say, with many many thanks to the Jesky's, that I am running
a new, total JR set up in the plane now, with very nice results so far. I
think I can go flying tomorrow, FINALLY, and not worry so much about
glitching.
Jim's last post seems to be the closest thing to the cause of this
dilemma. Looking at the characteristics of the problem, I just don't see it
being a result of "brand mixing." Looking at the issues, and looking at what
solved the issues, this seems to be the absolute most logical explanation
for what is happening.
I used to think PCM was just a more expensive way to perform a simple
task, but now I see that it is not. I can honestly say that I will not fly
digital servos on PPM any more.
Thanks a TON for everyone's input on this issue, it's all helped so much!!
See everyone in Muncie!
Scott Pavlock
On 7/6/06, J.Oddino <joddino at socal.rr.com> wrote:
PPM signals are analog, not digital. If there is noise introduced to
the system in the RF link it shows up as jitter (small changes in pulse
width at fairly high frequency) on the pulse width output to the servos. As
the range increases the noise increases and the jitter increases. The
digital servos have very tight deadband and will respond to the pulse
jitter. The analog servos may have a large deadband in which case they
would not respond to the jitter. A PCM receiver is a true digital device
and noise added in the RF link can not get through. If the noise gets bad
enough it will go into hold or failsafe but you will not get servo jitter.
Deadband is the range that the pulse width can change before the servo
will respond. A tight servo will respond with a pulse width change as small
as one microsecond.
I'm not saying this is the cause of your problem but it is something to
check. Hope this helps.
Jim O
----- Original Message -----
From: Scott Pavlock
To: NSRCA Mailing List
Sent: Tuesday, July 04, 2006 6:04 PM
Subject: Re: [NSRCA-discussion] Analog Servo RF Masking and....Thanks!
J.
Yes PPM / Dead band ?
In the problem set up they are all JR digital servos only. 2 - 9411sa's,
1 - 8411sa, 1 - 8417, 1 - 3421sa) they all are glitching.I'm not mixing
analog and digital at any time. The glitch has been as drastic as a violent
1/4 inch up and down movement on the elevator surface when we first plugged
them in after we received the system back from service to this constant
noise on all servos with no load.
Scott
On 7/4/06, Ed Alt <ed_alt at hotmail.com> wrote:
Scott:
OK, is any of the analog servos? Do the digitals also do it? (I
assume not). For example, I've noticed that JR 4721 and 4131 servos have a
cyclic response to most any JR digital installed on the same receiver.
Everything worked fine from a reliability/range standpoint, but there was
this small, regular interval "blit"; just a couple of degrees of movement
from whatever position the analog servo should have been remaining in. The
digitals were rock solid, the 4131 and 4721 just blitted a little bit. I
finally decided that I just wouldn't mix the 4131 or 4721 in a digital servo
environment and that was the end of it.
Ed
----- Original Message -----
From: Scott Pavlock
To: NSRCA Mailing List
Sent: Tuesday, July 04, 2006 8:06 PM
Subject: Re: [NSRCA-discussion] Analog Servo RF Masking and....Thanks!
Ed
WE used three different Rx two different brands all the same glitch
also put hole setup in my dad trainer same glitch also used my dads brand
new RX and TX same glitch. Used three different freq. same glitch.So we
tried a analog servo no glitch we replaced them all with analog no glitch
still no confidence in the system.
Scott
On 7/4/06, Scott Pavlock <f3aflyer7 at gmail.com> wrote:
Scott
I don't know if Tony put it on a shaker table or not but he did put
six hours in the system. And he really went out of his way to get it to us
asap.With the 4th holiday I've not been able to contact him, maybe tommorow.
While range checking the digis if I put my hand on the antenna the glitch
increased but with the analog there was no glitch at all. My father and I
have been working this problem for over a month we have replaced everything
or sent it in to be checked.Right now no glitches with analogs but again
will the glitch present itself as noticably with analogs as apose to the
digis.We have no glitch right now but still no confidence in the system.
Scott
On 7/4/06, Scott Anderson <scott at rcfoamy.com> wrote:
Hi Scott,
Stupid question, did you send RX out and have it put on a shaker
table and checked.. I had a RX issue for over a month and spent time with
Tony S. and he found a bad filter on the board..
Just my 2 cents from a fellow team member..
Scott Anderson
----- Original Message -----
From: Scott Pavlock
To: NSRCA Mailing List
Sent: Tuesday, July 04, 2006 6:29 PM
Subject: Re: [NSRCA-discussion] Analog Servo RF Masking
and....Thanks!
I've used multiple battery set ups including ones without a
regulator on a normal NiCd pack, and also on both a 5.6v regulator and a 6v
regulator.
John,
No I don't. I actually have no clue what that is haha.
On 7/4/06, John Pavlick <jpavlick at idseng.com> wrote:
Do you have access to an oscilloscope?
John Pavlick
http://www.idseng.com
-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org [mailto:
nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Scott Pavlock
Sent: Tuesday, July 04, 2006 5:40 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Analog Servo RF Masking
and....Thanks!
I've literally tried EVERYTHING possible to isolate the problem.
The only problem I can find is solely in the servos. The battery is bran new
(duralite 2s2p), bran new heavy duty MPI switch. I can reproduce the problem
with the digis with many different switch/battery/regulator set ups. I know
current draw isn't a problem as I've flown this set up for 2 years with no
faults.
On 7/4/06, John Pavlick <jpavlick at idseng.com> wrote:
Scott,
Well I'm sure you've been through a lot already, but what you
need to do is try to isolate the problem if possible. Start with a working
setup (the analog servos). Next, add 1 digital servo. If it still works,
remove that servo and try another. Only change ONE thing at a time. If it
works with 1 digital servo ALL THE TIME, then add a second one. If you start
to see problems as you add more digital servos (i.e gets worse with 3 or 4
digital servos but seems to work OK with 1 or 2), look at your battery and
switch. What are you using for a battery and switch by the way? If your
radio checks out OK (RF-wise) it's more likely that there is a problem with
power. I bet you didn't have Rx the batteries checked did you? As you know,
analog servos don't draw nearly as much current as digital servos. That
could be the problem. If you have any way to look at the voltage when all of
this is happening it could reveal some things. One way to do this is to put
a servo lead in an unused channel on the Rx, connect it to a voltmeter, turn
everything on and move the sticks. Don't use an Expanded-scale volt meter,
just a plain old DVM (or better yet an analog volt meter) will do. See what
that tells you.
John Pavlick
http://www.idseng.com
-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org [mailto:
nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Scott Pavlock
Sent: Tuesday, July 04, 2006 3:58 PM
To: NSRCA Discussion List
Subject: [NSRCA-discussion] Analog Servo RF Masking
and....Thanks!
First I would like to thank everyone for the great advice on
these last few posts I've posted. Everyone has been a big help.
I'd like to ask if anyone knows if an analog servo would mask
glitches coming in?
(2 - Futaba 3010's, 2 - Hitec HS77's, 1 - HS81MG)
When I connect my JR digital servos ( 2 - 9411sa's, 1 -
8411sa, 1 - 8417, 1 - 3421sa) I get a pretty significant, constant glitch,
as if the servos are constantly trying to center, but they have no load what
so ever. This is the problem I have described in previous posts.
When I connect analog servos in an identical set up, there is
no "noise" at all. I range tested them at 100 feet with 1 antenna section up
and there is no loss in speed and no sluggish behavior. I also range tested
this at about 300 feet with the antenna completely down just for kicks, and
I get the same results.
When I range test the digital servos, even at the 100 foot
range with the antenna completely extended there is a significant, constant
glitch. The servos, receiver, and transmitter have all just gotten back from
being checked and the 9411sa's had new pots put in, the receiver had been
re-tuned to the frequency, and the transmitter got a new antenna. I am very
surprised with these results as I just spent a fair amount of money to have
my electronics looked at and deemed well.
Now, my question again, are my analog servos just masking a
problem, or is this solely a problem in the digital servos?
Thanks a ton everyone!
Scott
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