titch

Hi
Has anyone got any experience of the relative merits of the hitec equivelent to the JR 8411 servo. On paper the hitech one seems to have similar spec. Wjhat i really want to know is what trade of is there in using the cheaper hitec digital servo compared to a JR 8411.

krayzc-RCU

My Feedback: (31)

i am running 8411 on 1/4 and larger birds. i think the hitec programmer makes its easy to set up multiply servos. i had to find match pairs for my 40% project elevators, i used the matchbox on the wings which require 3 per. All brands have their strengths and weakeness. Horizon and Hitec will change out your gears when needed for free. i think you will find happy campers on both sides of the fence...

P-51B

My Feedback: (5)

I use hitec analogs at the moment, and am ordering some digitals for bigger plane next week.

The Hitecs are less expensive, can be programmed, and (depending which one) equal or better performance.

There are guys at my field with both, never problems from either, everyone is happy with what they have.

Kris^

My Feedback: (1)

I sold or traded away most of my 8411's and replaced them with 5735's and 5945's from hiTec . .the 5945's are stronger mechanically, have better gear wear characteristics, as much torque, comparable accuracy, and cost $30 less each. I doubt I'll ever buy another JR servo.

Giant Scale

Both servo's are good, I prefer the hitec mainly because of the programmability and the lower price. I have owned both but the hitecs are so much easier to set up, especially in a multi servo per surface scenario. You can use a matchbox but this adds one more failure point. It all depends on what you prefer.

Lynx

As much as Hitec servos sound really good, keep in mind the failure mode for a Hitec servo has to be almost exactly the same as a matchbox. You say matchbox's aren't a good idea because that's one more thing to go wrong, but keep in mind the electronics in the Hitec servo that can go wrong as well (And did in early version of them) I can't argue about it, having the servo programmability is very very nice. But it does add a potential failure point above and beyond a normal servo. If you can afford to give up the better response and instant torque of the digitals a high quality standard servo is ALWAYS going to be more reliable than even a highest quality digital. There's just more to go wrong in a digital. More subject to EMI, who knows how it's going to glitch if a static shock takes out part of the controller chip. More subject to impacts because of increased complexity it's easier for a little nick to cause it to be unusable. A hundred other things could go wrong. Usually don't, but if you're talking about risk it's plain and simply higher.

davey_flyer

My Feedback: (4)

So what IS the advantage of using the HFP-10 - and how is it that using this you can match two servos? Can someone explain this to me? The process of matching? Do you do it with the servos mounted in the plane and the control surfaces attached and then plug each servo into the programmer?

Thx

JohnMac

[QUOTE]Originally posted by Lynx
[ If you can afford to give up the better response and instant torque of the digitals a high quality standard servo is ALWAYS going to be more reliable than even a highest quality digital. There's just more to go wrong in a digital. More subject to EMI,

Lynx,
Who says? I am still using my original digital servos that are more than 10 yers old. How much more reliable do you want them to be?
Regards,

John.

Lynx

You have to look at it from the point of an engineer, not a consumer. As a consumer, what works works. Engineering things you need to keep in mind what might happen. It's just a simple law of nature that the more complex a system is the more than can go wrong with it, so it's a point of fact that comparably solid constructions on a standard servo and a digital servo the standard will last longer. There's just more to wear out or break on accident. I'm not talking the rule either, I'm talking exception. Because you generally try to engineer something as if the worst thing is always going to happen. That way in the end you'll end up with above average system stability.

Kris^

My Feedback: (1)

Davey Flyer. . teh way I program servos goes like this.

Each servo has an arm. This is attached to a pointer, then I go into the "programming' regime for the servo. I first set ZERO, with the arm perfectly perpendicular to the servos body. I then set MAX throw left and right at 60 degrees off that center. Every servo I have is programmed int he exact same way, To the exact same end points. Max travel of a total of 120 degrees equates to 150% dialed in on the transmitter. Since the best resolution is 1 microsecond, and 1 degree wil equal 10 microseconds (in theory for a 1200 microsecond pulse width deviation), I have just programmed the servo for 1/10 degree increments throughout its maximum possible travel arc.

When reversing the servo, the travel remains the same, just the direction changes.

I also use the manual testing mode to set up control surfaces for which holes to use and how long the horns should be, for proper movement

Giant Scale

Lynx,
No where in my post did I say there was anything wrong with a matchbox. If I am going to gang four analog servos to a surface I will need to use a matchbox. I have not seen any data that digital servo are as likely to fail as a matchbox. I have not heard of a match box failing. All I was saying was that the more pieces of equipment you install in a plane the more failure points you have. After you use a programmable servo it is difficult to use anything else, they are just so much easier to setup.

mglavin

My Feedback: (31)

Digital servos are the same as there analog counterparts, except for a micro-processor. This is used to analyze the incoming RX signals and controls the servo motor. Digital servos use the same case, motors and gear-trains as standard servos. They also have the same feedback potentiometer [POT] as standard servos.

Digital amps are comprised of a quartz crystal controlled micro-processor, field effect transistors [FET] and heavier wire pigtails.

Analog amps are comprised of custom logic chips, timing components and standard pigtails.

Digital servos differ in how they process the incoming RX control signals and subsequently control power to the servo motor. Reduced deaband is realized, the servo reacts faster, accelerates and decelerates smoother and faster, resolution is greatly increased and holding power is incredible.

I dare say the only reason a digital servo might be considered more susceptible to premature failure is for the simple fact that the servo is working a larger percentage of time as compared to an analog servo, however I have yet to loose a Hitec digital. Crash wise I can attest to the durability of the digitals, seems no more or less likely to be damaged than any other servo. Gear sets and cases are likely to be damaged in the event of crash. Further additional physical damage is going to damage either equally.

It's kind of hard to compare apples to oranges, yeah there both fruit, BUT... I am a very happy Hitec digital servo consumer... I especially like the warranty... You breaky, Hitec fixey...

Lynx

From everything I've read I'll most likely end up going with mostly Hitec digitals anyways. I'm largely arguing semantic's. Sorry for being such a pest about it, I'll go back to my cage now and play nice =>
P.S. Anyone have any scoop on how the servo programmer works? Does it use the standard three wires or is there a special plug on the servo for it? I'm curious as to how the data is sent back and forth from the servo to the programmer, and if it's possible for accidental noise on the servo line to cause it to go into programming mode? I'd like as much input back on that as possible, especially whatever the Hitec guy will put forward. I'd like to make a programmer myself. Projects like that keep my busy during the winter.

JohnMac

Lynx,
I think the point has been answered already, there is nothing more to go wrong in digital servos than analogues, rest assured.I use Multiplex who invented this technology back in the early 90's. I understand that the same German guy designed the Hitec digitals and the same chip is used as the original MPX units. Interestingly MPX have dropped most of the programmability in their latest Digis, only the sense of rotation can be changed. They say that people did not want the programmability but want a lower price. Pity really, I used the programmer a lot.
BTW, what does the Hitec programmer cost in the US? I understand they are about £100 here and they have sold exactly 0 to end customers, just a few to retailers. It looks a much nicer unit that the rather fiddly units from Multiplex (cheap though!)
As for the servo inadvertently entering programming mode, it requires a piece of code to be sent from the programmer to both open then close the menu, just like on a computer Tx.
Regards,

JohnMac.

Kris^

My Feedback: (1)

The programmer has two ports on the side. . one for the servo, one for the standard "charge" jack for a battery pack. An on-board 1100 Mah NiCad pack supplies power after charging, or you can use an external battery pack to power the unit.

As for cost, the programmers go for about $150 here. It's hard to believe that "ZERO" programmers have been sold to end-users in England. Here in America it seems to be THE thing to have for servo setups and testing for ALL brands, as well as to program the HiTecs. Probably a cultural thing. . . Americans are just so darned independently minded. I would never even CONSIDER borrowing another persons programmer if I could afford my own.

JohnMac

Kris,
It surprised me too. The info came from the rep of the UK Hitec distributor about a month ago.
I think its more a case of the market position of Hitec here.
I was amazed when I first came on this site to see the high regard that you Americans hold for Hitec. It has made me examine my own prejudices. Here Hitec is thought of as cheap and poor quality, although that is gradually changing.
So I tend to see Hitec servos in the average clubs sports model and not in the Jets and Petrol models etc, therefore the owners don't need digital servo let alone programmable ones, and they probably wouldn't spend £100 on a programmer anyway.
Like I said the MPX programmers were functional but not as nicely done as the Hitec one (they did all the same things though) and they sold plenty. The first one back in '91 was about £35 (about $50) The second one for the V2's was £25 (about $37).
There arevthings you can do with programmable servos that can't be done any other way, like the slats on my F-86 which have a MPX micro MC V2 on each end. Thanks to the programmer the slats travel out exactly parallel and the same amount as each other. Might have to try some Hitec digis. (I will have fun telling this to the Multiplex rep tomorrow night!)
JohnMac.