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Noise from Digital Servos

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Noise from Digital Servos

Old 10-10-2002, 10:10 PM
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APC
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Default Noise from Digital Servos

I have just got some JR digital servos for my new heli. It is the first time I have used digital servos and they seem to make a relatively loud buzzing noise all the time like they are trying to move or something. There is no friction in any of the controls and every now and again they go silent like they aren't trying to move anymore (as I would have thought they should sound all of the time). This noise is with all of the controls just sat at mid points and not being touched.

Is this noise normal with digital servos or is there something I need to do ?

Thanks
Andy
Old 10-10-2002, 10:17 PM
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tsaldivar
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Default Digitals

You are now digitized!

Beautiful sound ain't it?
Old 10-10-2002, 10:19 PM
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Default Noise from Digital Servos

Thats what digitals do. But if they are fighting to hold center, it could mean there is something binding. If they are always fighting to hold center, or if you have two or more digitals ganged to a surface, be sure they are matched so the end points and centerpoints are exactly the same. Otherwise you will drain your onboard battery in no time, or worse yet, in flight. For ganged digitals, JR makes a match box for that.
For your situation, if you dont have ganged servos, you can probably just take the horns off and let the servos center by themselves (center the trim). Then mechanicallyadjust the linkages to drop right onto the splines of the output shaft. If its just an occasional buzz here, and buzz there, Youre fine. The buzz intensifies as the servo loads itself, You will get to where you can sense if the servo is overloaded.

Hope this helps

Digitals RULE, You will never want to go back to analog servos! :spinnyeye
Old 10-10-2002, 10:49 PM
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Default That is what they do

Yep they do the buzzy thing/
Old 10-10-2002, 11:24 PM
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Default Noise from Digital Servos

Thanks for your replies

Coulter_Dean :
The heli has CCPM so would teh buzz indicate that maybe it isn't adjusted quiet right. All looks to be ok as far as I can tell. I will try taking the links off and see if they buzz the same when not connected to the CCPM control surfaces.

There sure is a lot more to heli electronics these days than when I first tried flying them at Univerisity 8-9 yrs ago. I dropped out for a while as I couldn't afford the hobby whilst a student (or until I had a decent job so I didn't wince at any repair bills) then when I got back into it recently there is a whole new world of electronics and computer radios to learn. Unfortunately there isn't a heli flyer at my local club so I'm trying to understand it all myslef.
Old 10-11-2002, 12:12 AM
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Default Noise from Digital Servos

I know next to noting about helis, but the electronics are the same to me.
A digital servo will buzz if it has to support the weight of a surface. You just dont want it to be working its *ss off around center where most your flying is done. For me, even when they are not loaded, its rare for a digital not to buzz, Like I said earlier, You'll eventually train your ear to be able to tell if the servo is being overloaded. The buzz changes pitch and intensifies as the servo load increases.
Old 10-11-2002, 03:45 AM
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Default Noise from Digital Servos

You traded the sound of whirring gyros for the sound of digital servos to remind you to turn off your radio when not flying.

We needed that!
Old 10-11-2002, 04:45 AM
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Default Noise from Digital Servos

I am just curious.. I have taken digital servo's and hooked them directly up and they wouldnt have any thing even mounted to them not even the servo arm was on yet and they would still make a "buzzing" noise.. is that suppose to be that way?
clay
Old 10-11-2002, 05:06 AM
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Default Noise from Digital Servos

Yes, they are doing that because they are holding a very tight center.

Contrary to Analog servos that decrease their voltage as they near the center position (or the position that the stick is telling them to be), Digital servos apply full voltage in digital pulses no matter what position they are in. This is what gives them the tremendous "holding power" that they are famous for. They resist any movement with full voltage pulses. If they found a position where they didn't have to hold anything, that would be "deadband". You don't want "deadband". Even one "digit" would be "slop".

Analog servos try to narrow the deadband but since the voltage is so low around neutral sometimes it allows movement before the servo decides it needs more voltage in order to get back to where it is supposed to be. In the old days (70s) we use to hand select analog servos with such tight deadbands that they hummed. Sure, it drained the batteries faster, but, we had more precise control. Today we have Digital servos.

We must not think that Digital servos are the "cure all" or the best for everything. They are a tool that we should use in their proper application. Although they are tight and precise, they also pump alot of voltage into the motor and keep it very busy ALL THE TIME.

All that work being done by the servo motor trying to hold it's position causes not only noise and battery drain, but HEAT within the servo. You are already starting to see motor failures and heat sinks built into the servo cases. Digital Servos have their place and should be used only where needed.
Old 10-11-2002, 06:25 AM
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Default Noise from Digital Servos

Originally posted by TEAMERICA
All that work being done by the servo motor trying to hold it's position causes not only noise and battery drain, but HEAT within the servo. You are already starting to see motor failures and heat sinks built into the servo cases. Digital Servos have their place and should be used only where needed.

So should I take my 4 JR DS8411s out my .20 sized combat plane? I aways thought it was a good idea to have them!
Old 10-11-2002, 06:26 AM
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Default Noise from Digital Servos

hehehe, J/K!


Are digital servos faster and have more torque <not just holding power> because they are just much better quality than analog servos or does being "digital" also help increase the speed and power. I ask because all the high end "super servos" are digital. Is it possible for these "super servos" to have a non digital counterpart with the same torque and speed just without the dead band and precision? Kind of like high end cars have the extra bells and whistles that low end cars do not, but you can only have them if you buy the high end car even thought the low end car is just as possible to have those bells and whistles. I hope that makes sense.
Old 10-11-2002, 08:32 AM
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Default CCPM

Sorry, I have a stupid Question...
but what does CCPM mean?
(( Something )) Code Pulse Modulation? )) >? Close?
thanks
Jeff
Old 10-11-2002, 12:20 PM
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Default Noise from Digital Servos

CCPM = (Cyclic/Collective Pitch Mixing)
Old 10-11-2002, 01:12 PM
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Default Noise from Digital Servos

So should I take my 4 JR DS8411s out my .20 sized combat plane? I aways thought it was a good idea to have them!
NO, that is a good place to store them. The "down pipe" packaging will protect them and contain the smoke in case you ever turn them on.

Oh, you want to FLY them in a combat plane? Well, that would be a good way to make them heroes. . . . And you might get the award for the most expensive crash at a Combat meet. :stupid: Better yet, why not just send them back to JR and, with the change after you buy the postage, you can go out and get some REAL Cirrus Combat servos from HP. They are designed to last no longer than needed.


Are digital servos faster and have more torque <not just holding power> because they are just much better quality than analog servos or does being "digital" also help increase the speed and power.
Not only because they get the higher voltage all the way to their designated position but because they ARE better motors. They have been developed and selected for this particular job. When you think about it, that motor is starting and stopping and reversing many times each second. Just to hold a position. I have a friend that has them on a Giant Scale Sukhoi (three per aileron) and he jiggles them while he taxis out to take off. They jiggle so fast that the ailerons are a blur to me. Imagine what is going on inside the servo with the gear train and all that reversing.

I ask because all the high end "super servos" are digital
There are already many "High End" non-digital servos. They are rated for their speed and torque. You might also look into other things like the make-up of the motor and the gear train. I used 3-pole Airtronics motors in my Giant Scale Air Racer because we needed power and durability (94161). Some people thought they wanted power and speed and went for the Coreless variety. What a waste. Giant Scale Air Racers may go 200 MPH, but the course is large and smooth flying is the key. They never need the quick activity of the combat model.
Old 10-11-2002, 01:28 PM
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Default Noise from Digital Servos

The bottom line is - "select your servos for their intended purpose". No longer is the latest new servo the best for all applications. We have choices.

Digitals are great for the Tail Rotor. It needs quick positive response and has a relatively light load compared to the frequency it is activated by the gyro. On the other hand, I like a digital on collective for the holding power. This requires more power but is usually activated less frequently than the TR.

Throttle, of course get the fastest you can, but you don't need to break the bank on a digital. Most servos out run the carb anyway, but you want to give it every chance to out run the collective. Servos are rated on speed for a 60 degree ark. how much faster is it when you only move it 10% of it's throw? Is it worth that extra $50?

Your servo choice on Cyclic depends on your flying style. Beginners NEVER need High Dollar servos. Start with standard servos. As you learn to fly, you will feel what is lacking and what you want to feel next. You will KNOW when you are ready to upgrade. I see so many newbies selling off their $1600 trainer heli because they couldn't keep up with the cost. Someone told them to buy the best and we are all conditioned to think that $$$ means BEST! Not so. Do it Smart!
Old 10-11-2002, 07:52 PM
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Default Noise from Digital Servos

Well TEAMERICA, with a signature like that you must not be able to tolerate your last two posts!


Great information!


I ask because all the high end "super servos" are digital
I meant to say most high end servos are digital.

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