quote:

ORIGINAL: Kmot

Howdy,

I have some new Spektrum A6020 servos. I have two installed in an ai. Digital servos Whinerplane, for the elevators. I just powered them up for the first time, using a Spektrum 4-cell Rx battery. I am using a Y-harness. The servos are humming loudly when the stick is at neutral. If I move the stick slightly I can get them to quiet, but a few seconds later they hum again. I have also tried adjusting the trim.

Is it possible the Y-harness is causing this? If so, what can I do about it to cure the problem?

Is there something else I should be looking for?

Thanks!

Digital HV High  torque servos make a lot of noise at idle. The first time you run into that, you could swear they were just screamin'.  Just make sure your input voltages and current readings are correct and drive 'em. Current reading should be very close to zero at idle (e.g. .000 to.008 amps). Holding up the elevators takes just a little bit of current. Also, I do not run Digital servos with a Y harness. I put them in separate channels, on separate circuits and mix. Do not forget to activate the trim in the mixed channel, if you mix.

quote:

ORIGINAL: Kmot

Thanks Rich!

The 4.8V batt was only for the purposes of testing the servos. I am in the middle of installing equipment and trying to figure out where everything will go. I currently plan on running dual 6.0V batteries in this model because it will have five digital servos and it is 1/4 scale.

quote:

ORIGINAL: Kmot

I currently plan on running dual 6.0V batteries in this model because it will have five digital servos and it is 1/4 scale.

quote:

ORIGINAL: rcflyn4fun

Hey Tom,

Give a look to these and see what you think.
http://www.fromeco.org/Products/04FRCWO-430s/

Mike

quote:

ORIGINAL: chuckk2

Servos, particularly digitals, introduce noise on the receiver power buss.  That can be enough to cause servo buzzing,
You might try adding some capacitors and see if that helps.    Some of the RX NiCads have internal resistance that limits
current "spikes", and causes the output voltage to droop.

Seems like you are talking about two different conditions. 1.) using caps to filter off the "RF noise" the servos may introduce in certain situations and 2.) using caps to compensate for using too small of a battery, defective battery, or running the battery too low.

For 1.) The servo buzzing described above is audible noise (versus stray RF). Audible noise is what the OP was inquiring about. Just because you have servo's buzzing a bit, does not mean you have stray currents on the servo line. If you take an O-scope and check it out you will be hard pressed to find that stray current you are thinking about. I did it to mine when they were buzzing with a 400 Mhz scope and all that showed up was the current that was consumed moving the servos and the current consumed to hold up large control surfaces (e.g. Ailerons on a Giant, .etc.) I have seen a range of .002 to .008 Amps used to hold up an aileron. Again, he was not talking about stray RF and buzzing does not mean there is stray RF.

For 2.) If you need caps to hold up your voltage to operational levels, your power supply, connections and or distribution bus may be inadequate. Or you could have a servo about to fail. What I have seen is people trying to use large (HV or high torque) servos directly on a receiver buss. When you get to the point of using HV/High torque servos you need a power distribution system versus connecting the servos directly to the Rxer. With a power distribution system, the Rxer provides input to the power distribution system and the distribution system feeds the servos accordingly. This ensures all the power that is needed for the servo to function is delivered. This arrangement also provides buffering between the servo circuit and the Rxer buss. This buffering also precludes stray  RF signals from getting back down into the receiver. 

If you are Hell bent on not using a power distribution system and still need some added buffering, then a short term solution to stray RF on the Rxer may be a RF Choke made from a torroid with the offending servo wire wrapped inside and around it. The material of the core and the number of turns thru it decides the RF Frequency that will be ”choked.”  But that is only a possible short term solution. Something is wrong if you are getting stray RF into the Rxer. Long term, one needs to fix the source of the problem versus trying a bandaide to divert it. If the servos are high voltage/high torque and you are getting RF into the RXer from a servo, the problem most-likely is the RXer bus may NOT be able to consistently handle the current needed. If you are seeing voltage drops on the servo, one may think they need to add caps. The real answer is to look at the total current you are using and get a distribution system that meets the planes needs. Adding caps to keep the voltage up is another bandaide. The real problem needs to be IDed and fixed or sooner or later, the caps will not be able to cover for the real problem, as it gets worse, and the plane/heli crashes. Been there! Done that!

When figuring total current used,  Digital Servos can use current all at the same time (e.g. if you have 9 servos and each can use 1 amp, then you could conceivably have an occasional 9 amp draw.) Analog servos are only addressed one at a time. Consequently the draw for Analog Servos is only whatever you highest current using servo uses. That is one of more important reasons for using a power distribution system versus trying to feed Digital HV servos directly off the Rxer.

I have been froggin' around with my two Giants' Hitec servos. After doing a lot of reading, I began to wonder if I could quiet down my servos by increasing the deadband width a bit. According to what is out there to read, if you have the linkages correct and the control surfaces are free there should not be much buzzing going on. The more weight of the control surface, the more buzzing. But, for a normal application the buzzing is minimal. At idle, the normal buzzing is caused by the weight of the control surface. However, if you have the deadband set too tight, the servo could be "hunting" for the correct position and this causes needless wear on the servo, current use, and more buzzing. So,...

I picked hp a Hitec programmer and took a look at the deadband setting. It was as tight as you could get it (i.e. 1). I moved the setting from a 1 to a 4 and the buzzing in the servo stopped. I cannot notice any difference in control surfaces' responses. Occasionally, one of the elevator servos still buzzes, but a quick flip of the stick and the buzz is gone. Also, I can not detect any increase in the control surfaces' freeplay.

My conclusion is that the buzzing at idle can be reduced to nothing or almost nothing by increasing the deadband width a bit. The buzz is still there when moving the control surface, but for the most part it is totally gone at idle. According to the writings out there, this increased deadband setting may also reduce the wear and tear on the servo. Now  once thiesnow melts up here, well see if I can live with a DeadBand Width of 4.

Anyone else froggin' around with this? 

quote:

ORIGINAL: Kmot

I don't have a way to program my Spektrum servos. I have discovered though, that if I jiggle the sticks a bit the humming will stop.