Analog servos
#2
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I believe it's likely due to the higher voltage . i've used hs635, 645 etc with no issues. With 2.4 needing at least 6v, some of the analog stuff just don't handle it well. could use an in line regulator if you need to mix them in.
#3
Some of the older slower servos may have a hard time keeping up to the faster resolutions, when I went from a 9c to my 14mz I had to learn over again due to the increased speed on response.
#4
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Airtronics had issues with analog servos if you used their higher resolution receiver, they resolved the issue by offering a slower resolution receiver if you wanted to run analog servos. (I fly Airtronics) I never had any issues with Futaba or Spectrum receivers running analogs and have no experience with JR.
#5
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Myth, what you have to watch is like Randy said, running the higher voltage that Spektrum and some others requires to avoid brown outs. I lost two JR. retract servos on my Electra until I put a 5 volt regulator inline for that channel only, problem solved. The servos are getting pulse width commands from the RX the 2.4 RF link has nothing to do with it.
#6
As I understand it, digital servos can operate in parallel and analog servos operate sequentially. When each digital servo operates it can take over an amp up to 5 amps. When several Digital servos are operated the current usage is cumulative (i.e. 8 digital Servos could simultaneously draw as much as 40 amps, etc.) This caused a higher (higher than with analog servos) load on the same power supply as the Rxer. If the high load caused the voltage to drop below 4.3 VDC, then the Rxer would go into the condition we called brownout. Once the voltage recovered, the Rxer would recover. This problem was exacerbated by the people still trying to use the old 4.8 vdc NiMh packs (i.e. this low voltage pack had insufficient margin to even handle a couple good sized digital servos.)
Is this maybe what you were asking about?
Is this maybe what you were asking about?
#7
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I remember when everyone started converting to 2.4, most of the small analog aux. servos like JR341s and 351s had a nasty habit of briefly travelling full stroke when powered up on 2.4. If you had one on your gear valve, you could find your jet unexpectedly dropped on the pavement because of this. Airframes with externally mounted turbines sometimes got dings on the bottom of the turbine cans when that happened.
So don't use any old analogs on a pneumatic air valve with 2.4!
So don't use any old analogs on a pneumatic air valve with 2.4!
#8
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Interesting, I have a mixture of digitals and analog servos in my DV8R for the past 7 years, 300 plus flights with no issues. Spektrum RX using A123 unregulated batteries at 6.6 volts.
7 analog servos
4 digital servos
7 analog servos
4 digital servos
#9
HI all, need some info, when 2.4 came out , serval years ago, It was said, their might be some issues useing anolg servos.
You can choose the resolution in the setup, once set to the lower setting the problem disappeared.
Also had a problem with digital & analog servos sharing a Y lead with the Futaba 14 channel receiver
on the first 4 channels. Solved by just using different channels & mixing them together.
Fact or myth
My experience? The issues can be simply overcome. That's for Futaba, can't speak for the other radios.
John.
Last edited by Boomerang1; 11-04-2014 at 11:06 PM.
#10
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Hi Guys,
I run Airtronics gear, both -1 & -3 receivers with Analog servo's with out any issues. I use HD1501 MG, Airtronic 94102 and 94322 servo's on all my models now, with both -1 & -3 receivers with out any issues. Some say that -1 Airtronic Rx are for analog servo's and -3 for digital. But I've had no issue with the HD1501MG servo's on either Rx. All my gear is 2.4 and I made the transition several years ago, with my 72 meter gear stated to act up at our flying field. I was flying Ch. 38 with my old gear and when the new cell phone towers went up...it created havoc with my models. I do not use digital servo's and my choice after seeing to many models self destruct using them at our flying field.
Aloha,
Bobby of Maui
I run Airtronics gear, both -1 & -3 receivers with Analog servo's with out any issues. I use HD1501 MG, Airtronic 94102 and 94322 servo's on all my models now, with both -1 & -3 receivers with out any issues. Some say that -1 Airtronic Rx are for analog servo's and -3 for digital. But I've had no issue with the HD1501MG servo's on either Rx. All my gear is 2.4 and I made the transition several years ago, with my 72 meter gear stated to act up at our flying field. I was flying Ch. 38 with my old gear and when the new cell phone towers went up...it created havoc with my models. I do not use digital servo's and my choice after seeing to many models self destruct using them at our flying field.
Aloha,
Bobby of Maui
Last edited by Bob Paris; 11-04-2014 at 10:49 PM.
#11
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rcpete, please cite the source of that notion. The RF section, modulation and center frequency have nothing to do with it.
Now, Futaba 2.4G RX, R6208SB for example, only state analog cannot be used in the high speed mode(intended for higher resolution when using digital servos). They recommend running in normal mode for analog. Perhaps something like this gets taken out of context leading to that notion about analog and 2.4
And then the choice of supply voltage is separate matter. It is well known that some old Futaba servos were rated for 4.8v only and documented as such. Most others up to 6v. I dont think I ever saw specs to 6.6v or beyond until HV came along but people run them successfully on LiFe anyways. 10% overvoltage may be within the characterization window.
Now, Futaba 2.4G RX, R6208SB for example, only state analog cannot be used in the high speed mode(intended for higher resolution when using digital servos). They recommend running in normal mode for analog. Perhaps something like this gets taken out of context leading to that notion about analog and 2.4
And then the choice of supply voltage is separate matter. It is well known that some old Futaba servos were rated for 4.8v only and documented as such. Most others up to 6v. I dont think I ever saw specs to 6.6v or beyond until HV came along but people run them successfully on LiFe anyways. 10% overvoltage may be within the characterization window.
#12
As I understand it, digital servos can operate in parallel and analog servos operate sequentially. When each digital servo operates it can take over an amp up to 5 amps. When several Digital servos are operated the current usage is cumulative (i.e. 8 digital Servos could simultaneously draw as much as 40 amps, etc.) This caused a higher (higher than with analog servos) load on the same power supply as the Rxer. If the high load caused the voltage to drop below 4.3 VDC, then the Rxer would go into the condition we called brownout. Once the voltage recovered, the Rxer would recover. This problem was exacerbated by the people still trying to use the old 4.8 vdc NiMh packs (i.e. this low voltage pack had insufficient margin to even handle a couple good sized digital servos.)
Is this maybe what you were asking about?
Is this maybe what you were asking about?
4.8v batteries are only at 4.8v when they are completely flat, they charge to 6v and operate happily around 5.6-5.7v. It's why JR '4.8v' servos are happy at 5.8-5.9v, it's the voltage they were designed to work at!!
its how the servo motor is powered/controlled that makes the difference between digital and analogue servos. Manufacturers have different ways of doing this in both types, some cope, some don't.
#13
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I have a Futaba 12Z on 2.4 with a 14channel receiver. Use Hitec Digitals on rudder, elevator and ailerons. Hitec 645MG on Flaps and Steering, dual A123 6.6v packs without regulators. 2 Jets set up the same way. One has an Orbit Power Jack, the other a 12 channel SmartFly. Never a problem.
#14
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My experience with Airtronics high resolution was the digitals were happy as clams but the analogs were freaking out, jittering and moving all over the place. Once I replaced the receiver with the lower resolution one everything calmed down. There is even an addendum to the Manuel that addresses this issue. Not a myth at all, just painful reality.
#15
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I almost lost my hotspot after switching from JR9303 72 MHz (100 flights) over to 2.4 futaba. HS running all Hitec 645MG. First flight on the HS with 2.4 the jet was all over the place...landing gear going in and out during flight. found out the Hitec 645MG would be ok then suddenly glitch full deflection and go back to normal. replace them with JR and it's ok.
Last edited by basimpsn; 11-05-2014 at 08:08 AM.
#16
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HI all, the reason I brought this up was, when going over the Bandit, I noticed JR 2721 servos for the flaps. They have never been a problem, very quiet little boys, just doing their job.When I think about it, the JR 1221 receiver/ PB is in all my jets, and never a problem with Hitec minies for gear/ smooth stop.
Rcpete
Rcpete
Last edited by rcpete347; 11-05-2014 at 07:07 AM.
#22
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Aloha,
I'm also building a large gas twin engine (AMR) model and bought a V2 Spectrum 18 channel radio for the model. I am using HD1501MG servo's on this model as well as Hitec 225mg's for the throttles and 85mg's for the choke control. So far, I've not witnessed any problems. I'm using Spectrum Rx's for 18 cannels I'll need for the model. Electric start takes up two channels, choke two, throttle two and engine cut off one. I'll also have one channel for my Twinsync with the new electronic ignition module (it does away with the old electric pick up system they used - no more magnets and pickups - sold by Down and Locked).
I've tested on the bench the whole system with no issues. I'm also using a Servo Power Box, to drive my flight controls - ailerons, flaps, elevator & rudder - with a yaw dampener tied into my Rudder.
This now kind of confuses me and wonder if I made a mistake with my servo choice. All the servo's I selected for this project I've used before, for years with out a problem. The HD1501 servo's have never failed on me, the Hitec HS225HD are powerful for their size and will drive the throttles with ease and the choke servo's HS85MG's will drive the choke functions-on/off only.
I guess I'll have to wait and see what happens, but if anyone is using the V2 Spectrum 18 channel radio with these servo's and have issues, please chime in and let me know.
Soft Landings Always,
Bobby of Maui
I'm also building a large gas twin engine (AMR) model and bought a V2 Spectrum 18 channel radio for the model. I am using HD1501MG servo's on this model as well as Hitec 225mg's for the throttles and 85mg's for the choke control. So far, I've not witnessed any problems. I'm using Spectrum Rx's for 18 cannels I'll need for the model. Electric start takes up two channels, choke two, throttle two and engine cut off one. I'll also have one channel for my Twinsync with the new electronic ignition module (it does away with the old electric pick up system they used - no more magnets and pickups - sold by Down and Locked).
I've tested on the bench the whole system with no issues. I'm also using a Servo Power Box, to drive my flight controls - ailerons, flaps, elevator & rudder - with a yaw dampener tied into my Rudder.
This now kind of confuses me and wonder if I made a mistake with my servo choice. All the servo's I selected for this project I've used before, for years with out a problem. The HD1501 servo's have never failed on me, the Hitec HS225HD are powerful for their size and will drive the throttles with ease and the choke servo's HS85MG's will drive the choke functions-on/off only.
I guess I'll have to wait and see what happens, but if anyone is using the V2 Spectrum 18 channel radio with these servo's and have issues, please chime in and let me know.
Soft Landings Always,
Bobby of Maui
Last edited by Bob Paris; 11-05-2014 at 01:30 PM.
#25
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HI all, the reason I brought this up was, when going over the Bandit, I noticed JR 2721 servos for the flaps. They have never been a problem, very quiet little boys, just doing their job.When I think about it, the JR 1221 receiver/ PB is in all my jets, and never a problem with Hitec minies for gear/ smooth stop.
Rcpete
Rcpete
The first and last time I mix brands.