digital vs analogue
 

what is the main differences between these servo types? I know digital has full torque every degree of movement where as analogue only has full torque at full throw... but what advantages are there for using digital rather than analogue?

RE: digital vs analogue
 

Digitals also seem to start moving a little quicker and they generally center easier.

Are they really necessary? I think it depends on what type of flying you are into. For general sport flying, the average pilot might not notice much difference. When you start getting into serious precision flying, advanced 3D and stuff like that though, the digitals might provide a lot of advantages.

I have many analogs and quite a few digitals.

RE: digital vs analogue
 

Centering, holding, torque, and precision

http://www.futabarc.com/servos/digitalservos.pdf

RE: digital vs analogue
 

add cost.

CGr.

RE: digital vs analogue
 

I agree on centering and torque. The Digital servo has a little magnetic device that does the centering, while the analog has some type piece that has to manual center it, so it wont center as well. Also, the torque is greater. You get greater torque because the digital servos have magnets in them ( as i understand ), which helps the torque.</p>

RE: digital vs analogue
 

Hi,

All the above is true and I'll add that you know when your model is turned on as digital servos BUZZ.:D

Cheers,

Colin

RE: digital vs analogue
 

It's a safety THING.............at least that's what the manufactures would say.:D

RE: digital vs analogue
 

Chuck, Barracuda and CG pretty much covered all the bases. I use them both and I even mix them in planes as required. For most sport pilots flying there 4*s you would never notice the difference, I was even using them in my 60 size Kaos. The digitals hit the market and started getting the big hype about 8 or 10 years ago, before that everyone used analog. For most pilots they are not needed but they do work as advertised. When I buy servos today they are all pretty much digitals but I don't buy into the hype about needing all that power {money} because most planes don't require a 100 lb. aileron servo. A lot just depends on the plane.

RE: digital vs analogue
 

I will add to what others have said. While all above have pointed out pluses of the digital servos there is a minus that needs to be taken into consideration. Digital servos use more power than their analog counterparts. When an analog servo centers the servo moves to the center and WAITS for it's next input. A digital servo moves to center and then it continually updates itself to stay in the center (this is why they buzz). This constant updating uses up power that an analog servo doesn't. This is not a huge deal with the large battery capacities that are available today, but it is something that needs to be considered. If you are moving up from analog servos to digital you will need to increase your battery capacity too.

Ken

RE: digital vs analogue
 

digitals center better, they hold the control surface in place much better. i think torque has to do with the actual motor not if its digital or analogue, digital or analogue has to do with how the information from the reciever is processed.

RE: digital vs analogue
 

The increased torque does have to do with the fact that it is a digital. Digital basically just refers to how it pulses the motor I believe. Analog servos pulse the motor at a fixed frequency and vary the pulse width to increase torque/speed. Digitals pulse at a much higher frequency and also vary the pulse width. This means that digitals deliver more energy, quicker so you get better speeds, more immediate torque and higher torque. The downside to that increased energy delivery is quicker battery depletion as was mentioned. The link that Barracudahockey provided explains it much better than I probably am.

RE: digital vs analogue
 

thanks you guys... convinced that I need digital...

RE: digital vs analogue
 

You never told us what plane you intend to use these servos on. Since this is a beginners forum, we have to assume that you are not building a large scale gasser or large 3D machine, or a 2 meter pattern plane, which is pretty much where you would use digitals for. Most manufacturer's higher torque servos will work for larger models that beginners or those with a couple of years of experience would use.

So, a recommendation to switch to digital would be off the issue here. The OP requested to know the differences... that's quite different from a recommendation.

When I bought my DX7, it came with four DS821 servos that Spektrum describes as digital high torque servos. They are fine servos and cost about $30.00 US. But, they are not true digital high end high resolution servos that cost three or four times as much.

Consider what the need is before you select something that is way over what you need and will cost you a small fortune to use.

CGr.

RE: digital vs analogue
 

Assuming similar specs, the torque is the same, how fast it's available is what's different. The motor position is updated much more frequently from the servo amplifier. Updating the motor position more frequently as Ken correctly pointed out, uses more power. The more frequent motor position updates are what accounts for the increased holding power as well.

I'll add that there are some very fine analog servos and some very ........uh........crappy..........digital servos so that alone shouldn't be your sole decision maker.

RE: digital vs analogue
 

"Like the concept of having digital", "want to say the plane has digital", "think having digital would be neato", all legitimate reasons for buying digital servos for 99% of flyers. "Need digital" is for about 1%. (No scientific data to back up percentages). I put Hitech coreless analogue servos on my last plane, a Pitts Super Stinker, and I'm not good enough to tell the difference. When I let go of the elevator it flies level, so I assume they center just fine.

RE: digital vs analogue
 

With the proliferation of high performance planes like Yaks, Extras, Sbach's you can definately tell the difference if you can so much as fly knife edge or do a snap roll.

Any intermeidate helicopter pilot can tell the difference.

Any competition pilot can tell the difference.

If you fly a platform like that enough to get familiar with it, then install decent digital servos, a good percentage of the pilots will be able to tell the difference.

Putting in circles in a cub, probably not so much.

RE: digital vs analogue
 

As we are in the Beginner's forum there is another point that can be made. Please remember, this is in the context of Beginner/Intermediate pilots in here. An Indy race team will easily spend hundreds of thousands of dollars to shave even a few hundredths of a second off of their time. Now for those of us driving to work each day, we would never even be able to tell the extra speed gain so spending that kind of money is a waste. What does that mean for servos?? It means that most of those in here at this level of flying would never be able to tell the difference between analog or digital servos as they just aren't going to be doing things that the digitals will be a benefit for.

Does this mean that you shouldn't buy them? Not at all. If you really want them then by all means buy digital servos. But do a hard honest look at ask yourself do you really need them?? If not then save the money and get a good analog servo!! To be honest, I've been flying for 14 years and the largest part of my servos are good old Airtronics 94102 standard analog servos. These servos are a real workhorse and will do quite a bit. I don't mind spending money on digital or higher torque servos when I need them, but I'm not going to spend the money on them just so I can tell everybody I have digital servos!!!

Ken</p>

RE: digital vs analogue
 

Well,

Over here I gotta agree with RCKen, and I apply the rule of economics what is your priority, if you priority, your plane requires the digital servos, do that, what if it's just you want to check how do they work. I'm happy with standard servos. I'm still using FM 72 Mhz TX and RX, simply I can't afford 2.4 GHz, can't even afford now to buy a plane, just got a check today in my ban account and wife made a list of bills and grocery shopping. I believe if things are working good for you, don't switch to something more expensive and stay within your limits. These are my thoughts and I'm not using it as an advice for anybody. Just sharing it:D

Happy flying

Mody

RE: digital vs analogue
 

Mody, I just ordered a Hitec 2.4 Module for my 9-C, $20.00 + $5.00 for shipping and you have to send them in a standard old module. Working or not!! It will be a while until I can afford any RXs but it is a starting point to get into 2.4 and still keep my trusty Futaba!! Offer good until the end of this month. Back to SERVOS: First digitals I bought were the lowest price Hitecs i could get, I would have to go look at the number but I think they were/are the 5475s at $35.00. They work just fine and yes, I can tell the difference between them and a standard servo but it depends on the plane and the stunts. They are carbonite gears so they are used in my smaller glow powered planes. Depending on what I have on hand at the time I mix servos very often, I use digitals on the elevators and rudder and may use analogs on the ailerons. Even on my big planes i still use a good BB analog for throttle. I'm in the same boat as Mody so I tend to use what I have on hand for my planes and save my money for things like the electric bill. If you can afford digitals then by all means buy them, they will be with you for a lot of years so you may as well get them now. If not then analogs work just fine!!;)

RE: digital vs analogue
 

Gray Beard,

Your response is really encouraging, I saw a guy at my field using Hitec Aurora 9, I saw it and I was literally drooling, so it was something that I can touch it but can't have it. Aurora 9 is a little much outta my league thing. I'm using JR's XF421 EX FM 72 Mhz old 5 channel radio. I don't think it has any option to have the module replaced. Gray, I'd like to ask you which Hitec radio model you have and which module you ordered for it for just $20 +$5 shipping?. I have everything except for an ARF, my sharp focus is on Hangar 9's Mustang Sports 40 which is $199+shipping otherwise if I'm unable to get that much amount, I'll go for LA flyer which is $110 or try to find something outta craigslist. Today I had money but major chunk is gonna go towards bills. Anyway, I'm expecting to have a plane may be in the mid of june:D hopefully. I'm desperately missing my flying.[&o]

I wish ya all the best Gray:D

Mody

RE: digital vs analogue
 

Gray Beard mentioned something that I am dealing with now. I have a combination of servos, some digital, some analog, and some analogs with higher torque, plus a few mini Hitec HS-81. My question is, where is the highest torque needed on a plane? The rudder, because of steering on the ground? Can I use an HS-81 for throttle without ball bearings or metal gears? Do ailerons require more torque/speed than elevator? I guess if we want to get scientific, it would have to depend on the airspeed, area of the control surface, and required response rate. But that is too much math for my simple mind.

RE: digital vs analogue
 

Let me give you a simple perspective. If I'm flying a $400.00 airplane; just putting around doing easy maneuvers; a $15.00 analogue servo will do me just fine. If I'm putting a $4,000.00 plane in the air; doing hard maneuvers; I'm going to spend whatever it takes on digital servos (and every other accessory for the airplane; like batteries, control links, etc.); just for the peace of mind. Thanks; Ernie P.

RE: digital vs analogue
 

hsukaria,

It's a good question, what which control surface needs digital servo, but the question arises that every plane has the same control surface but different throws. Apparently I think that 3D flyers need their plane's control surfaces bigger than regular flyers, more throws on their elevator, rudder and aileron. I think it all depends upon your flying and your model which one you are flying. I'm very least experienced here, and I always share my thoughts, I most of the times try to learn from people's experiences as there is no short-cut for experience. Your question is good and I think we all know the answers according to our needs, planes and flying.

Mody

RE: digital vs analogue
 

OK, first to Mody, if your radio doesn't have a removeable module in the back your out of luck. I have an old Futaba 9-C radio and the Hitec module just pops in the back. Jr sells the module also and you can get them for JR and Futaba then be able to use there type of RX. hsukaria, the most force generated on our RC planes are the rudder and elevator so I always install my best servos there. The ailerons don't require all that much force so my lesser servos go there. I have often used the HS 81 or 55 on throttle depending on the room in the plane. I have some pretty big planes {sometimes} and I like a standard ball bearing servo with a high speed on the throttle just for the smoothness and speed. This is just a general statement from me, others do different things but a lot depends on the plane itself. Most of mine land in the IMAC or Pattern types. 3-D is a total different story. I don't/can't fly 3-D other then a hover or two so I'm not the best one to answer this. 3-D planes have such large surfaces and they are under constant movement they require the high end digital servos, both speed and power. I have some big servos in my 30% Extra and all digital. My friends with 40%+ planes have some huge servos compared to mine. Buy the best gear you can afford and you won't be disapointed and it will be with you for a long time. Mine sure has. If you can't afford it then get the gear that will work with the plane you have and as you move along in the hobby you can upgrade. The old gear will still get used, don't worry too much about it.

RE: digital vs analogue
 

Gray,

Well, my Radio is JR XF421 EX, and You can look up the pictures of the back of my radio on google images. I picked up an image from there, and most likely I understand that I'm outta luck. As this model is easily 5 years old. I'm gonna attach a pic of the other radio which is JR's different analog model not digital. So I can understand I'm outta luck, I don't think it has any slot to be replaced by 2.4 module.

Thanks

Mody