SaCCaL72

My Feedback: (1)

What is the advantage if any of a Digital Servo over an Analog Servo. I can't decide which to use for my Aeroworks Edge 540T .46-.61. After looking at a lot of different Futaba servos both digital and analog, they seem to both contain the same qualities with torque and speed, what is the difference other than price? Servos I narrowed it down to in my price range:

Futaba
Digital 6.0V
S3050 - Rudder - 90oz. - .16 (sec/60) - $49.99
S3152 - Ailerons and Elevator - 87oz. - .18 (sec/60) - $32.99

Analog 6.0V
S3010 - All the way around (Because much cheaper in price) - 90oz. - .16 (sec/60) $24.99

Would it be an advantage to have the digital or would the analog be sufficient for 3D/Aerobatic type flying. I have a Futaba 7CAP radio with the PCM receiver. Are there any other servos you might suggest, doesn't have to be Futaba. Thanks in advance for your help.

BarracudaHockey

My Feedback: (11)

Analog servos use less power but develop their peak torque after some movement, 10 degrees or so if I remember right.

Digitals center better, develop their peak torque immediately (less than 1 degree rotation) and hold thier position better but use more power (drain the battery faster) Will you notice a difference? Yes. Will it be worth the price difference, especially on that size plane? That choice is yours.

SaCCaL72

My Feedback: (1)

Would it be better to have higher torque on the rudder and elevator or rudder and ailerons or elevator and ailerons?

Sport_Pilot

High torqe servos still will not develope max torque till the servo is several degrees from center. A digital servo a half degree out will have more torque than a high torque servo that is two degrees from center.

BarracudaHockey

My Feedback: (11)

If you're running dual servos on the ailerons but the best servos on the rudder and elevator if your going to be doing a bunch of snap style manuvers or knife edge.

SaCCaL72

My Feedback: (1)

The throttle servo doesn't matter as much, am I correct?

BarracudaHockey

My Feedback: (11)

You are correct.

SaCCaL72

My Feedback: (1)

Thanks barracudahockey, so I guess the best setup would be the S3050's on the Rudder and Elevator and the S3152's on the Ailerons. Does it matter that the rudder/elevator will be slightly faster than the Ailerons? And that the aileron servos don't have metal gears? Thanks...

BarracudaHockey

My Feedback: (11)

I doubt you would notice a difference. 3152's all around would probably be fine, even over kill, we aren't talking about a 30 percent monster here.

SaCCaL72

My Feedback: (1)

True, it isn't a giant scale or anything, I was just thinking that because I am throwing in a Saito 100 it may need a little more torque and the metal gears, but your right, I know it probably is overkill and what is a 3oz difference really gonna do, so the 3152's all around will probably do as it will save me a little $$ also. I might still just throw a S3050 on the rudder just to make me feel good as it is a pull-pull system, maybe not... hmmm... Thanks again...

e-sailpilot86

The only thing I have to add, is I have the 3151's and the 3152's. The 3152's are digital, but I noticed they're not as precise as the 3151's. However, I recommend the 3152 instead, if you intend on running 6v. the 3151 cannot take 6v, only 4.8, the 6v will be wonderful. It's really surprising how precise the digitals are over the analog servos, if you have them in an application where you will notice them. Imagine putting digitals in a gentle lady....

SaCCaL72

My Feedback: (1)

e-sailpilot86, . Actually I think the 3151's do take 6V. I know it doesn't say it on the Futaba sight but I saw it on the Tower Hobbies sight saying it took 6V and when I called Futaba, I had one person last year say it didn't and then this year when I called they said it did. So I hooked up my H9 Texan which has 3151's in it with a 6V battery and it seems to work ok on the ground, haven't flown it yet though. Now, I don't know if the longevity of the servo will be as long with 6V, but it worked as far as I know. I will probably get the 3152's and maybe 1 3150 for the Rudder, not sure... Thanks for your help!!!

JasonS

A HUGE part of what determines the need for a digital servo is the kind of throws you are running.
If you are running pull-pull setups or 3D throws, digital is very helpful. With 3d throws on large control surfaces, even a high torque analog servo feels like you have rubber bands for control linkages. Which makes It much harder to avoid flutter, not to mention a lack of precision.
When I swapped out some really good analog servos (9303 Futabas) for some med range hitec digitals on a 24% Sukhoi, it flew like an entirely different airplane. Then I tried some hi-end digitals (JR 8411) and saw another jump in precision and "groove". You really do get what you pay for with most servos.
Granted, on a smaller ship the differences may be less noticeable.


On a 3d style airplane, elevator and rudder seem to benefit the most, but as large as the Ailerons are getting on some of these ships - it can make just as much benefit there too.

dougwill

JasonS
Thanks for all the info. Dumb question. Is a different receiver or transmitter req'd. for digital? I have a JRxp 662 and 700 rec. Also will 4.8vt. 1000 mah give satisfactory performance with digital?

Doug

SaCCaL72

My Feedback: (1)

dougwill,
No, you shouldn't need anything different for digital servos. Just as long as your radio is FM or PCM, NOT AM.

dirtybird

My Feedback: (5)

Digital servos are better than analog but they are not that good.
I have tested about 28 servos both digital an analog. (actually they are both analog servos but the name digital seems to have stuck).
Usually the analog takes about 15 degrees to develop its maximum torque while the digital takes about 1/2 that. The best servos I have tested is the Futaba 9152 and the Hitec 5995. They both take about 4 degrees to develop maximum torque.

BarracudaHockey

My Feedback: (11)

With digitals they use more battery power (mah) because they are always producing full torque. A 1000 mah will be fine for power output but you need to keep an eye on the post flight voltage, preferably with a loaded volt meter. Always check pre flight for the first flight and immediately post flight thereafter as your charge will come back up after sitting for a bit and you won't always see the true condition of your battery. Not trying to scare you but you need to keep an eye on it.

dirtybird

My Feedback: (5)

Not true. The battery power consumed depends on the load.

BarracudaHockey

My Feedback: (11)

Digital servos will ALWAYS use more power than an analog servo in the same application.

You also have to be careful to set your control surfaces up correctly and with no binding or they will suck down a pack like a camel drinking water if they are stalled.

dirtybird

My Feedback: (5)

Again not always true. It depends on what digital and what analog servos you are comparing

BarracudaHockey

My Feedback: (11)

Ok how's this. Among comparable servos for a given application digitals will generally consume more power than analog servos.

Panzlflyer

My Feedback: (15)

That doesnt seem to be true either!!!
Hitec 945 Coreless NON digital 400mah No Load operating =400ma
Hitec 5945 Coreless Digital No Load operating = 280ma
I lifted the figures off Servo City web site as they do a good job of listing the specs.
Suprised me as those 2 servos are the same except amplifiers

BarracudaHockey

My Feedback: (11)

Lets try not to confuse the issue with semantics, stats or who can be smarter. The bottom line is, in the real world, most all of the time, digital servos will work better but at a higher price and higher current drain. They also are less forgiving of sloppy control installations.

dirtybird

My Feedback: (5)

I think the quy that wrote that spec was smoking something.
I would guess the 945 at 40ma no load and the 5945 at 100ma no load.
In fact my test of the 5945 shows the operating current is 100ma with a load of 4 oz-in. I have not tested the 945 but I do know it is the same servo as the 5945 without the digital amplifier.

dirtybird

My Feedback: (5)

I can agree with that.
I am not smarter than anyone else. In fact in some areas I am downright dumb.
Its just that I have spent the last three months testing the servos I have, and provided by others.
I find the specs provided are wildly inaccurate and cannot be trusted.