maktec

My Feedback: (29)

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

exeter_acres

My Feedback: (2)

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!

j.duncker

My Feedback: (2)

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.

bubbagates

My Feedback: (32)

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

exeter_acres

My Feedback: (2)

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

doubledee

My Feedback: (4)

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

Cyclic Hardover

My Feedback: (3)

$$$$$

BarracudaHockey

My Feedback: (11)

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

doubledee

My Feedback: (4)

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

BarracudaHockey

My Feedback: (11)

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.

skiman762

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.

BarracudaHockey

My Feedback: (11)

Some digital servos are programmable.

bruce88123

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.

Swager

My Feedback: (1)

"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!

MikeEast

My Feedback: (3)

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.

bruce88123

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.

doubledee

My Feedback: (4)

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

bruce88123

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.[]

skiman762

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


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

opjose

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.

MikeEast

My Feedback: (3)

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.

opjose

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.

MikeEast

My Feedback: (3)

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...

bruce88123

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.

bruce88123

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.