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Futaba FP-S128 servo.


David Davis 2
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9 minutes ago, EarlyBird said:

From a UBEC or ESC using a two cell Lipo battery for example.

 

From what I have read a four cell NiMh pack should be used if it's not supplying the RX. If supplying the Rx a five cell NiMh can be used because when the Rx is switched on the voltage will drop to acceptable levels. However, with a regulated supply the voltage will be maintained at 6v when the Rx is switched on, which is not good for the servos. Which takes us into disputed territory as some say it works fine and others say it's not in accordance with the manufacturer's specification. Not a problem in this case as NiMhs will be used.

 

This is my understanding from what I have read, confirmation would be good.

 

Steve

 

 

 

The current drawn by the Rx will not cause an appreciable voltage drop to any battery that's capable of running even just a single servo.

The Futaba servo spec sheet can only refer to both 4.8v & 6v as Gary posted.

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1 hour ago, EarlyBird said:

From a UBEC or ESC using a two cell Lipo battery for example.

 

From what I have read a four cell NiMh pack should be used if it's not supplying the RX. If supplying the Rx a five cell NiMh can be used because when the Rx is switched on the voltage will drop to acceptable levels. However, with a regulated supply the voltage will be maintained at 6v when the Rx is switched on, which is not good for the servos. Which takes us into disputed territory as some say it works fine and others say it's not in accordance with the manufacturer's specification. Not a problem in this case as NiMhs will be used.

 

This is my understanding from what I have read, confirmation would be good.

 

Steve

 

 

 

Not true. The current drawn by the receiver is minimal and should NOT be relied upon to drop the battery voltage.

 

Ah Pat beat me to it. Didn't spot it on next page.

Edited by Gary Manuel
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charge up a 5 cell nihm battery, let the voltage settle down for an hour then fly, that will prove the septics are wrong.

 

most of my stuff runs on 5celle the only exception that I am ure that runs on 4 is my Rafale with its Futaba s 9404  4.8v servos in the wings.

 

Ok a bit messy but my old Robbe Futura running on 5 celles Futaba s 9205/9202/3010/3001 servos all as you can see on the voltage tester running on 6v, and has done for around 10 + years, no magic smoke 'yet' 😆

 

 And yes I have chanded the servo rocking system, it is now on a Beast x flybarless head.

20220814_170338.jpg

Edited by Paul De Tourtoulon
yes this is one on 41,,, not 2.4,,,,
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13 hours ago, Paul De Tourtoulon said:

charge up a 5 cell nihm battery, let the voltage settle down for an hour then fly, that will prove the septics are wrong.

 

No, it won't. 

 

It'll prove you got lucky.

 

Exceed electrical specs at your own risk.

 

No sceptics on this thread that I can see. A few posters are offering sound advice though. 

 

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17 minutes ago, Nigel R said:

Exceed electrical specs at your own risk.

The electrical specs are what I am struggling with. Is the max voltage 4.8 or 6.0? The manual says both, but the servos have 4.8 on the label. Apparently, my interpretation that 6.0v is only when driving the Rx is wrong. 

 

Steve

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32 minutes ago, EarlyBird said:

The electrical specs are what I am struggling with. Is the max voltage 4.8 or 6.0? The manual says both, but the servos have 4.8 on the label. Apparently, my interpretation that 6.0v is only when driving the Rx is wrong. 

 

Steve

If it's 4.8v on the servo then it's 4.8v and not 6v, probably because because it was one of the radio sets sold with rechargeable battery's and not AA cells, différant markets, in France most were sold for AA battery's.

Edited by Paul De Tourtoulon
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      The OP  asked if it was worth changing the servos in an old WW1 model that comes out two or three times a year. I fly a similar model but changed elevator and rudder servos to 3001s a couple of years ago

          I noted in my post the testing of some even older servos but would not use them in a flying model.

             

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On 14/08/2022 at 08:14, Paul De Tourtoulon said:

 

 

 

It's ok jon I also built my own radios, receivers servo amplifiers and repaired cb and boat radios,   that was a long time ago but volts are still volts,,,

 

 It feel like I am standing on the side of a boat relieving myself against the wind,,,,🙃

 

sorry but if offended can the last remark be struck out by the moderators,,,

 

 

 

Ok, you built your own bits and pieces. Thats great, but you presumably selected components capable of doing the job and so have an intimate knowledge of of your equipment. However, you didnt design, develop and build the other servos you mention so your point is redundant. This is why i dont recommend everyone runs out and puts 7% oil through their OS engines. I think it would be fine, but i dont know for sure as i didnt build it so i will recommend something known to be safe. My recommendation of 15% might be lower than the 18% in the manual, but i know enough about the subject matter to know 18% is ok. 7% may not and i do not want my recommendation to be responsible for a crash, but this prospect dosent seem to worry you at all. 

 

Combined with your 'charge up a 5 cell nihm battery, let the voltage settle down for an hour then fly, that will prove the septics are wrong.' comment and your apparent light heartedness at the thought of a serious failure by saying 'no magic smoke 'yet' with a laughing smiley, i am not offended, just horrified by your attitude. 

 

 

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40 minutes ago, J D 8 said:

      The OP  asked if it was worth changing the servos in an old WW1 model that comes out two or three times a year. I fly a similar model but changed elevator and rudder servos to 3001s a couple of years ago

          I noted in my post the testing of some even older servos but would not use them in a flying model.

             

 

Ultimately, if there is even a slight doubt about the safe operation of your radio equipment it should be replaced. For the sake of a £10 servo, why risk it. 

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2 hours ago, Paul De Tourtoulon said:

If it's 4.8v on the servo then it's 4.8v and not 6v, probably because because it was one of the radio sets sold with rechargeable battery's and not AA cells, différant markets, in France most were sold for AA battery's.

That's the reason for different voltage specifications, which you knew all along. Does this mean that your advice to use 5 cell NiMh packs for 4.8v servos should be followed?

 

Steve

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40 minutes ago, EarlyBird said:

That's the reason for different voltage specifications, which you knew all along. Does this mean that your advice to use 5 cell NiMh packs for 4.8v servos should be followed?

 

Steve

NO, my advice was for the standard 4.8v / 6v servos, at no time did he mention that it had 4.8v written on them, why  didn't he mention that in the first place ?.

 

Off to fly my DLE 20ra in my P 47, and it's 5 cells no magic smoke in 4 years of it flying.🥳

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5 minutes ago, Paul De Tourtoulon said:

Yes what am I going to do all day, I am only hoping a certain 'expert' can post some more information,

just changing a couple of springs, ok enough is enough I will give it a rest for a while.🤐

 

 opps too late,,,🤣

 

Do you think you are funny? I cant decide i you are trying to be funny or are actually serious. 

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Time to give the text sparring a rest.  Some recent posts don't reflect well on the posters and we can't allow things to deteriorate to name calling or personal attacks.

 

The manufacturers' information isn't crystal clear...specifying 4.8v or 6v leaves room for debate as to whether these are actual measured values or nominal voltages for 4 and 5 cell NiXX packs but although it seems fairly clear to me, reference to Futaba is the only way to confirm the matter one way or another.

 

Simple electrical theory would confirm the view that as voltage increases, so do currents through components and there may well be be a reduction in life but if the servos are designed to operate within certain limits then the manufacturer must have judged that any extra heat can be dissipated safely for a satisfactory service life.  It's arguable though that too low a voltage might result in a stalled servo which could easily lead to overheated motor windings. Use an appropriate servo within the designed servo power supply limits to avoid unnecessary failures.

 

Let's not continue to argue over the manufacturer's intention - various parties have expressed their opinions so let's allow forum users to consider the opinions stated and make up their own minds.  I would suggest that if anyone can't interpret the instructions or specifications supplied with their servos that they contact the manufacturer for clarification.

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I have learned a lot from this topic, which is why I joined this forum, manufacturers did supply for 4x1.5v packs and 4x1.2 Nicad packs which is taking me a long way back. This meant that servos were either designed for 4.8v or 6.0v power supplies and obviously they used the nominal battery voltages as everyone did. The servos had the design nominal voltage on the label to indicate which battery technology to use and the manual covered both versions. Throughout this topic everyone has been referring to the 4.8v with the exception of Paul. This has caused a lot of confusion as he appeared to be saying 6.0v could be used on 4.8v servos and had done it for years. Until I asked pointedly if he was saying a 6.0v power supply could be used on 4.8v rated servos.

The answer.

6 hours ago, Paul De Tourtoulon said:

NO, my advice was for the standard 4.8v / 6v servos, at no time did he mention that it had 4.8v written on them, why  didn't he mention that in the first place ?.

That's the beginning and end of the antagonism, I hope, as it all comes down to a simple misunderstanding. 

 

Interesting that, IMO, a simple misunderstanding has made a more informative topic in the long run.

 

Steve

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To add a little balance - hopefully without stirring the pot - the Futaba website used to have an FAQ page where they specifically discussed the use of 5 cell packs with the then current range of servos.  I don't recall them making any distinction with earlier types.

 

EDIT

...and from the horse's mouth via the magic of the Internet Wayback Machine: https://web.archive.org/web/20060311130339/http://www.futaba-rc.com/faq/product-faq.html#q26 - note that this covers elements of both sides of the argument!

 

Can I use 6v (5 cell) receiver packs with my Futaba receiver/servos? Will I get increased performance from my equipment? Are there any drawbacks to using 6 volts?

All Futaba systems are designed to operate on either 4.8 volts (NiCD 4 cells) or 6 volts (Alkaline 4 cells OR NiCD 5 cells), except certain servos which are specifically labeled for use at one voltage or the other only. Some manufacturer's systems are not designed for and do not operate well on 6 volt, but most Futaba equipment handles the increased power input and provides increased performance, speed and torque.

Please note that while 6 volts provides you more torque and speed from your servos, it also provides you a significantly shorter run time for the same milliamp hours of capacity and may shorten the life of your servos proportionally. This sounds confusing, so it may help to compare the current in the battery to water in a bucket. If you have four small holes in the bucket, the water will come out at a certain rate. Add a fifth hole the same size, and you're supplying more water (increasing the current and therefore making the servos stronger AND faster); however, the bucket empties 25% sooner than when it only had four holes.

Edited by Martin Harris - Moderator
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