Big feet

Hi guys,
I don't want to start a small war here but what are your views on this one?
I understand that a digital servo will have better centreing than an analogue one but at the expense of higher power consumption.
I currently have JR591 servos in my Titan, (0.24 sec, 5.1Kg) except the tail which has the 401/servo combo as suggested by more experienced people than me, and it works great.
However, is digital really neccessary for cyclic and collective??
I have looked at reviews of the Titan and note digital 7.9Kg servos in use by some, BH for one in the review posted here on RCU.
As I am not at the hard 3D stuff yet are the 591's ok, or should I upgrade? If so is the torgue more important than the 'digitalness'?
Oh yes, do the digitals just install like 'normal' servos, I saw something on a Hitec servo spec about it being programmable, it was a 5625mg I believe.

My head hurts. [:-]

Thanks for the help.

soop7667

Digital has it's advantages. As far as high power consumption, that's for sure. I figured, I'd rather make the initial investment and have the digital's, chances are if you really get into it, you're going to want digitals later on anyways, so why wait?

I run a 4000 Mah Lipo through an Align 6X BCE w/glow driver and I get round about 8 - 10 flights on that.

rcjon

Soop,

>>I run a 4000 Mah Lipo through an Align 6X BCE w/glow driver and I get round about 8 - 10 flights on that.<<

2nd reference I've seen to Align 6X in the past week. I googled it and get no hits. Got a supplier and a cat #?

Jamming

Digital servos use more power mostly on start up and do require more mill amperes than analog while they run...But the 12%to20% extra power consumption during flight is well spent...If you run 6v on some packs it will overheat the internal electrics and smoke them...So be sure and check requirements of the servo...I run JR 2400 MAH NIMH batts on all three of my titan's...The JR 591s are a poor choice for heli's for many reasons...Mostly because of there slow response time 0.24 at low torq...You would be better off with a low priced Digital such as the Futaba 3151 or maybe Hitec's Hs5625Mg both are good choices for heli's...I have flow the 3151's in a titan with smooth 3-d with no problems at all...And have had really good luck with the 5625mg Hitec's They have very high torq for such a low priced servo...You will also have a lot easyier time learning with a faster servo thats Digital...More locked in feel if you know what i mean...Good Luck...

invertmast

My Feedback: (23)

http://www.alignrcusa.com/index.php?...roducts_id=630


its what we are running on all of our 600N's, i'm about to put one on my Avant FX too

rcjon

Thanks for the link Invermass.

Looks the "Combo" deal everyone offers has a LiPO battery. Do you remove it from the heli to charge?

Is the 5.8 V output OK for a GY401 or do you step it down?

Big feet

Thanks for the info guys,
Jeff, I was looking at the Hitec 5625's and they do look good, almost 8kg torque. I noticed as well that the Futaba servos have less torque than the JR591's, 4.9 compared with 5.1 for the JR, all be it with a faster response time, 0.02sec faster. I don't think I can think that fast, errr, can I have time to think about this one? [&:]

I had been thinking about changing the 591's since I first noticed servos mentioned in these fourms, I just have no experience of digitals.

soop7667

I don't step down the voltage on my Align Voltage Regulator for my 401, but I'm also using a HiTec Digital Tail servo capable of running @ 6V. Consequently, running it @ 6V makes it faster than a Futaba 9254.

BarracudaHockey

My Feedback: (11)

This is true mainly of tail servos and high frame rate stuff like governors. Most 4.8v rated servos will do ok on the Align regulators that run at 5.8v and even the 6v regulators, though personally, if choosing a regulator I'd get a 5.1 or 5.3v

Leo Wong

I am sure this article can help you or not,which introduce the advantage and disadvange of the digital servo.
Do you know the Advantages of Digital Servo?

Higher resolution-less deadband, more accurate positioning
1. Faster control response-increased acceleration

2. Constant torque throughout the servo travel

3. Increased holding power when stationary


The "Analog Servo" has custom Logic chip and timing components
The "Digital Servo" has a microprocessor,FET amplifier.

There are two main categories of servos available, analog and digital. Analog servos have been around for quite some time, servos work by sending pulses of power to the servo motor, similar to the way an ESC powers an electric RC truck. However Digital servos have significant operational advantages over analog servos, but with these advantages also come minor disadvantages, and this fact file will try to explain the positives and negatives of Digital servos in simplified terms.

First of all, a digital servo is the same as a traditional servo. Digital servos have the same motors, gears and cases as analog servos and the greatest difference between them is on the controlling circuit, the Digital Servo has a Quartz crystal controlled microprocessor, FET amplifier, which has a decisive influence on the performance of servos.

Where a digital serve differs, is in the way it processes the incoming receiver information, and in turn controls the initial power to the servomotor. Due to a small microprocessor inside the case, can specifically tailor the pulses being sent to the servo's motor. It can also send a larger number of pulses, which means that the range of motion can be broken down into a much finer pattern. Since more pulses are being sent, the servo is more responsive and contains a significantly less amount of deadband.

In a conventional servo, no power is being sent to the servomotor. When a signal is then received for the servo the move, or pressure is applied to the output arm, the servo responds by sending power/voltage, is pulsed or switched On/Off at a fixed rate ,creating small 'blips' of power. By increasing the length of each pulse/blip of power, a speed controller affect is created, until full power/voltage is applied to the motor, accelerating the servo arm towards its new position.

In turn, as the servo positioning pot tells the servo's electronics it is reaching its required position, the power blips are reduced in length to slow it down, until no power is supplied and the servomotor stops.

The Distinct Advantages of a Digital Servo.
First, it equips with the microprocessor, to receive the incoming signal and apply preset parameters to that signal before sending its pulses of power to the servomotor. This means the length of the power pulse/blip, and therefore the amount of power sent out to activate the motor, can be adjusted by the microprocessors program to match its function requirements and therefore optimize the servo's performance.

The second, is that a digital servo sends pulses to the motor at a significantly higher frequency. This means that, as opposed to the motor receiving 50 pulses/sec., it now receives 300. Although the length of the pulses is reduced in a direct ratio to the higher frequency because the power is being turned on/off to the motor more frequently, the motor has more incentive to turn. This also means that not only does the servomotor respond faster to the commands, but that increases or decreases in power for acceleration 态deceleration are able to be transmitted to the servomotor far more frequently. This gives a digital servo an improved deadband, a faster response, quicker and smoother acceleration/deceleration, and better resolution and holding power.

The Disadvantage of a Digital Servo.
Digital servos are definitely more advanced than their analog counterparts. However there is one disadvantage to digital servos, they use more power. Digital servos will drain a battery quicker than an analog servo would. Also running multiple digital servos is generally a bad idea due to the added current draw that they can pull when operated together. In situations where multiple digital servos are used, such as planes, special wiring and extra batteries are the preferred route.

Digital servos are the future for model control, and anyone who has used them says the difference is so significant that they would never return to analog servos, if there is a digital one available to fit the application.

Big feet

Leo Wong,
Thank you for the detailed reply, very useful information.