Digital servos what is the difference??
 

Do they need special receiver or other special equipment?
Thanks
Happy Flying
George

RE: Digital servos what is the difference??
 

no....

they do draw a little more current though, so a larger mAh battery is recommended,,,,



once you go Digi, you'll never go back!

RE: Digital servos what is the difference??
 

No just connect them up and enjoy better holding power. This means that they will not be blown back so easliy.

BUT BE PREPARED FOR A SUBSTANTIAL INCREASE IN RX BATTERY DRAIN.

EXPECT TO USE 2 OR 3 TIMES THE JUICE PER FLIGHT.

A minimum rx battery might be 1800 mah.

RE: Digital servos what is the difference??
 

George,

you get these benefits

More torque
Better centering
A bit faster in response

And that is on 4.8 volts. On 6 volts you get even more of all three.

I agree with everything else that was mentioned

RE: Digital servos what is the difference??
 

I use 1350 mAh batteries and get plenty of flight time.........

RE: Digital servos what is the difference??
 

They also give more precise movement, which is required for precision 3D flight. They do use more battery power because there is signal being sent to them all the time. Analog servos only have signal input when they are being moved. Frankly, digital servos are not really needed for everyday "boring holes in the sky" flight. They are essential for precision fllight of any kind. Unless you intend to do precision 3D or pattern I personally don't think digital servos are worth the extra money. Maybe your money would be better spent in buying a 6 volt battery. Just my opinion. :)

Regards,
doubledee

RE: Digital servos what is the difference??
 

$$$$$

RE: Digital servos what is the difference??
 

Analog servos receive the same position update as digitals do with each cycle of the position pulse train, it may be telling it to stay put but they are still getting updated.

here's a white paper by Futaba the describes the differences
http://www.futaba-rc.com/servos/digitalservos.pdf

RE: Digital servos what is the difference??
 

Sorry, I miswrote. I meant that the analog servo was not receiving signal when a idle, but it appears neither is the digital servo. The digital servo simply receives the signal to move at a higher rate, hence, sooner than the analog servo. I stand corrected.

Regards,
doubledee

RE: Digital servos what is the difference??
 

Your basic misconception is that its not recieving a signal. They all do. Then they compare the pulse width they have been sent to their current position. If its the same the servo doesn't move, if its different the servo moves.

The way it works is the transmitter sends out a string of pulses, with each channels stick position encoded in it from channel 1 to whatever. Its broken down in the reciever and sent to the individual servos where they update their position and starts over again at channel 1.

RE: Digital servos what is the difference??
 

Digital Servos vs Analog Servos

Digital servos, at the user end, are controlled no differently than analog servos. The difference is in how the servo motor is controlled via the circuit board (amplifier). The motor of an analog servo receives a signal from the amplifier 30 times a second or at 30Hz. This signal allows the amplifier to update the motor position. Digital servos use a high frequency amplifier that updates the servo motor position 300 times a second or at 300Hz. By updating the motor position more often, the digital servo can deliver full torque from the beginning of movement and increases the holding power of the servo. The quick refresh also allows the digital servo to have a tighter deadband.

With the exception of a higher cost, there are only advantages for digital sevos over analog servos.

The digital micro processor is 10 times faster than an analog servo. This results in a much quicker response from the beginning with the servo developing all the rated torque 1 degree off of the center point. Be aware that this faster response also results in higher starting currents, so make sure your batteries can handle it.

Digital servos can be programmed for direction of rotation, center and end points, failsafe option, speed, and dead bandwidth adjustment. This is great for matching sets of servos for deadband width, center and end points in giant scale aircraft applications, and for reversing a digital servo when two are used on a "Y" harness. If you do not want to deal with the added complication of programming, no worries! Hitec digital servos will perform like standard servos out of the box. It is not required to program them before use.

The standing torque of a digital servo is 3 times that of its analog counterpart. This means digital servos are typically smaller and have more torque.

What about servo modification? Digital servos are also modifiable, just check the datasheet to make sure.

RE: Digital servos what is the difference??
 

Some digital servos are programmable.

RE: Digital servos what is the difference??
 

In an analog servo the voltage applied to the motor is anywhere between 0 and full battery voltage (either direction). It only draws a small amount of current to maintain position unless there is a heavy load on the surface. In a digital servo the the voltage applied to the motor is either 0 or full battery voltage, nothing between. It is pulsed (in microseconds) by the processor to control the correct position. It is almost constantly moving (buzzing) incrementally in minute bursts to remain in the desired position which is one of the reasons why it draws more current.

RE: Digital servos what is the difference??
 

"Boring hole in the sky"

boring: tedious, dull, dreary, tiresome, lackluster, unexciting

Wow! Next time I'm flying, I have to remember to remind myself what a "boring" time I am having!

I guess you have to fly precision 3D or pattern to have a non-boring time!

Some comments on this forum just simply amaze me!

RE: Digital servos what is the difference??
 

There is a fundamental advantage that you guys have not mentioned in laymans terms and that is holding power. Here lies the real applied advantage of digitals.

For Example, and this is just a basic non technical explaination. With an analog servo, if you pull back on the elevator to full up elevator an analog servo sees a signal to move. It puts out a given amount of current and the shaft rotates. It does not care how much or how many degrees the servo shaft rotates or what the deflection of the servo arm is, its just deals out a certain amount of "power" basis your stick input. So if you are flying and the wind pushes back on the surface the current to the servo does not change and the servo gets "pushed back". It may rotate 30 degrees on the ground and only 29, or 28 or 25 degrees depending on headwind and how fast you are going. A digital servo in the same situation will increase power to hold the position of the shaft and thus the servo arm which means the control surface does not get pushed back.

With a digital whatever you ask for it gives you and will increase power (or whatever) to hold the servo shaft/arm in the place you told it to go with the stick. I guess you could sort of say that an analog signal thinks in term of power delivered to the servo and the digital actually thinks in terms of % of potential rotation of the shaft. Thats very laymen so dont cream me for it.


Not a great explanation since I am not an electrical enginner, but that is the jist of it.

RE: Digital servos what is the difference??
 

I also don't agree with doubledee that digitals are "required" for precision flight. They may make it easier but a good installation of analogs and a good pilot and a good plane will do just fine.

RE: Digital servos what is the difference??
 

Swager,
This may come as a surprise to you, but there are many words in the English language that have more than one meaning. I did make a mistake in the spelling as I meant boreing instead of boring. If your reading comprehension was any good you would have known what I meant, everyone else did. But, I suspect you already knew that and only wanted to write some smartass comment.

Have a nice day.
doubledee

RE: Digital servos what is the difference??
 

Uhhhh, sorry doubledee but "boreing" isn't in the dictionary. You did spell it correctly the first time but Swager chose to use the incorrect meaning.[:o]

RE: Digital servos what is the difference??
 

Here's a great info page from futaba click on the
orange tech info button


http://www.futaba-rc.com/servos/digitalservos.html

RE: Digital servos what is the difference??
 

What? How can that be?

I have both digital and analog servos on many planes.

If I turn on my plane and radio, it centers the analog servos.

Then if I manually push on any surface to change the position of the control surface, thereby moving the analog servo...

IT MOVES RIGHT BACK TO CENTER.

Likewise if I hold it at a particular position and move the surface, it goes right back to that position.

As soon as there is any force moving the control surface away from the commanded servo position, the analog servo starts pushing the surface back to where it was.


The servo want to go back to a particular position.

That doesn't correspond to the above.




I've purchased several planes that while they call for digital servos, but could do just as well with a good set of high torque servos.
For average sport fliers there are many times when the extra cost of the digitals is not needed.

RE: Digital servos what is the difference??
 

Your last comment is absolutely correct. Most analogs are great for sport flying. Good ones are even good for precision flying but you need a higher torque rated analog servo to overcome the pushback of the airflow than you would need with a digital,, torque rating being equal..

You hit the nail on the head in your post with your scenario..


I may not be very good at crisply putting it in text but I am pretty sure that is the general way it works.

RE: Digital servos what is the difference??
 

Ah ok. Thanks now I get it.

Makes sense....

As to the last lines ...the radio is commanding that the servo be at a specific "point", so if the analog servo is pushed off this position, then because the radio is telling it that it should be at say 25 degrees, the servo attempts to move back?

---

Conversely from what you are saying, the digital servo tries all the harder so to speak to hold the 25 degrees.

RE: Digital servos what is the difference??
 

Well I am not exactly certain about the relationship between the Transmitter and the servo, but in general, it is my understanding that a digital servo translates the input signal from the transmitter into a specific position of its shaft (or something liking to that thought line), whereas an analog servo sees the signal as a certain amount of current it supposed to use to turn the shaft but is not cognisent of its shaft position in relationship to that signal. An analog servo understands the signal as "here are some electrons,,, do what you will with them".. A digital servo understands that the transmitter is saying "here are some electrons, use them to go to 20 degrees shaft deflection and if thats not enough, I have more" Up to a certain point of course.

Thats my understanding.


Speak up gurus.... I dont want to mislead anyone here... I am trying to translate MY understanding of the difference in digitals and analogs into understandable terms but heck I could be totally wrong I suppose since I am not an electrical engineer...

RE: Digital servos what is the difference??
 

That's why there is a position feedback potentiometer inside the analog servo to tell the amplifier "where" the servo "is" at any time. It can then calculate how much power(voltage) to apply to get back to where it belongs. The further off it is, the more power it applies. As I said earlier, the analog applies a variable voltage. The digital is more like a pulsed on/off switch that switches (at a very high speed) the full voltage.

RE: Digital servos what is the difference??
 

All servos have a varied DC voltage level sent to the servo from the RX. No fancy pulse train or code. All of that is eliminated in the RX. That is why any servo will work with any RX basically as long as the pin arrangement is correct. You have Power, Ground & DC Signal wires to the servo, nothing more. Digital servos THEN convert the analog (yes they all have analog input) signals, into digital format to run the motors in the servo.

RE: Digital servos what is the difference??
 

So what is the performance advantage of say a 100in/oz digital over a 100in/oz analog all mechanical things within the servo being equal..

Learning something here.[8D]

RE: Digital servos what is the difference??
 

With the right TX, Accuracy and repeatability?

RE: Digital servos what is the difference??
 

My best GUESS is that the advantage is that the digital will put the FULL power to the servo for even the smallest output move. Whether that be to actually change the position or maintain the previous position. An analog that only wants to move a short distance (or maintain position) will only apply a partial voltage to the motor. That voltage will increase as the servo is forced out of the desired position.

Both have the same "absolute" amount of torque available, it's a matter of how quickly you can bring it into action. I GUESS in the analog situation it's like a "worst case scenario". Since the analog is only generating this torque "on demand" and the digital is always at high torque, I think you can see where some of the extra current drain comes from.

RE: Digital servos what is the difference??
 

read the futaba tech info it's all there in black and white and since they make them they should know

RE: Digital servos what is the difference??
 

My reading comprehension can only be as good as your spelling. I took the meaning exactly as I read it. I realize there are many words in the Engli......... Ah, heck with it, you're not worth the effort!

RE: Digital servos what is the difference??
 

as mentioned... the Digi is at full torque at every step.. meaning that at 1 degree or 60 degrees swing you get full torque... with analog... the servo needs to turn a bit before it has its full torque....

and the centering is the other thing.....

RE: Digital servos what is the difference??
 

Having now read how Futaba does their servos I realize they do NOT ramp their voltages but use a different pulse frequency and width to the motor. The result is the same however.

RE: Digital servos what is the difference??
 

So it's safe to say that for pure accurate control Digital wins hands down over Analog
If you need them or not is something you need to decide for yourself
If your type of flying needs good tight control then get them if your happy with the way your plane flys with Analog don't

MAN LAW??????

RE: Digital servos what is the difference??
 

Only if you have a high resolution 2048 type TX to go with them.

There was another great thread on this stuff where it was found that using digital servos with a regular TX does not produce any increase in accuracy, because the TX's resolution.

The synopsis... even 1024 resolutions TX's do not cut it...

RE: Digital servos what is the difference??
 

Sheesh, some people are just never happy.

RE: Digital servos what is the difference??
 

Do we have to be? ;)

But there is a valid point to be made...

Unless you have a high quality TX, the digital servos aren't buying you much if anything...not even accuracy.

I made the mistake of buying a bunch of good digitals for my my Funtana 90S as the instructions called for them...

Then I read here that my computer 7 channel TX did not have enough resolution to make the digital servos worth it.

I could have save a bundle and gone with high torque standard servos instead.

I even tried a set of cheap High Torque MG Tower Pro servos (14.00/ea) on another plane and I am getting similiar performance to the expensive digitals.

Of course your mileage may vary, and I'm no IMAC flyer.

RE: Digital servos what is the difference??
 

lol he spelled it right, you read it wrong, and he's still the one who screwed up? God, I love the internet. Coulda just admitted you were wrong and move on.

RE: Digital servos what is the difference??
 

ok what radios have the 1024 and which have 2048?

RE: Digital servos what is the difference??
 

I see it's those high dollar 12 and 14 channel tx

so does that mean the guys that have a 1000 bucks in digital servos using a 9 channel are not getting any advantage over analog servos ?
I'm confused now

RE: Digital servos what is the difference??
 

You still get the advantage of nearly instant full torque and they should center the same every time.

Everyone I know with a larger chopper that goes to digitals over comparable analogs says it feels like a different heli.