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Old Nov 11, 2006, 12:11 PM
Gary Spence
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n/a Posts
Futaba S3003 servo current draw?

What is the current draw on the servo while running? Not just the idel
current.

Know it will varry with load but a nominal value will be a good start.

Tried the Futaba site to no avail.

Thanks for any help

Gary


Old Nov 11, 2006, 12:11 PM
The Natural Philosopher
Guest
n/a Posts
Re: Futaba S3003 servo current draw?

Gary Spence wrote:
> What is the current draw on the servo while running? Not just the idel
> current.
>
> Know it will varry with load but a nominal value will be a good start.
>
> Tried the Futaba site to no avail.
>
> Thanks for any help
>
> Gary
>
>

Dunno but 9gm HS55's peak at about 250mA, a bigger one might be up to an
amp or so.

Plug a meter in and try...
Old Nov 11, 2006, 02:11 PM
Bill Fulmer
Guest
n/a Posts
Re: Futaba S3003 servo current draw?

"Gary Spence" <whob4me@mindspring.com> wrote in message
news:tzn5h.5761$ig4.410@newsread2.news.pas.earthli nk.net...
> What is the current draw on the servo while running? Not just the idel
> current.
>
> Know it will varry with load but a nominal value will be a good start.
>
> Tried the Futaba site to no avail.
>
> Thanks for any help
>
> Gary
>


Figure on 125ma, but it can easily go as high as 3-4 amps with large control
surfaces at high speeds...

Cheers,

Bill




Old Nov 11, 2006, 02:11 PM
Six_O'Clock_High
Guest
n/a Posts
Re: Futaba S3003 servo current draw?


"Bill Fulmer" <grafix01@cox.net> wrote in message
news:U3p5h.12984$tH2.6119@newsfe20.lga...
> "Gary Spence" <whob4me@mindspring.com> wrote in message
> news:tzn5h.5761$ig4.410@newsread2.news.pas.earthli nk.net...
>> What is the current draw on the servo while running? Not just the idel
>> current.
>>
>> Know it will varry with load but a nominal value will be a good start.
>>
>> Tried the Futaba site to no avail.
>>
>> Thanks for any help
>>
>> Gary
>>

>
> Figure on 125ma, but it can easily go as high as 3-4 amps with large
> control
> surfaces at high speeds...
>
> Cheers,
>
> Bill
>


To date the testing we have done tends to indicate STANDARD servos (42 to 50
ounce inch range) stall at about 250 to 270 ma. It is reasonable to assume
that higher torque servos draw more power.


Old Nov 11, 2006, 08:11 PM
Boo
Guest
n/a Posts
Re: Futaba S3003 servo current draw?


> Figure on 125ma, but it can easily go as high as 3-4 amps with large control
> surfaces at high speeds...#


That's complete bollocks - you'll never draw an amp out of a 3003, more like
1/4 to 1/2 an amp absolute tops. You only get just over an amp from something
like a 9450, let alone a piddly little analogue device like the 3003.

--
Boo
Old Nov 12, 2006, 06:11 PM
Gary Spence
Guest
n/a Posts
Re: Futaba S3003 servo current draw?

Thanks for the help. Got it (motor only) working on 12 volts. Only using
the motor with limit switches for an open /closed servo.

Cant get a reading with our meter as it is digital and to slow ro read
before the servo hits the stop.

Gary

"Bill Fulmer" <grafix01@cox.net> wrote in message
news:U3p5h.12984$tH2.6119@newsfe20.lga...
> "Gary Spence" <whob4me@mindspring.com> wrote in message
> news:tzn5h.5761$ig4.410@newsread2.news.pas.earthli nk.net...
> > What is the current draw on the servo while running? Not just the idel
> > current.
> >
> > Know it will varry with load but a nominal value will be a good start.
> >
> > Tried the Futaba site to no avail.
> >
> > Thanks for any help
> >
> > Gary
> >

>
> Figure on 125ma, but it can easily go as high as 3-4 amps with large

control
> surfaces at high speeds...
>
> Cheers,
>
> Bill
>
>
>
>



Old Nov 12, 2006, 08:11 PM
Bill Fulmer
Guest
n/a Posts
Re: Futaba S3003 servo current draw?

I'm surprised you haven't let the smoke out of that servo... It's designed
to operate on 6VDC max... It may work a while as long as you're not using
the internal circuitry.. But I'll bet stall current will cause a meltdown
in short order...

Bill

"Gary Spence" <whob4me@mindspring.com> wrote in message
news:5iN5h.6269$ig4.4881@newsread2.news.pas.earthl ink.net...
> Thanks for the help. Got it (motor only) working on 12 volts. Only using
> the motor with limit switches for an open /closed servo.
>
> Cant get a reading with our meter as it is digital and to slow ro read
> before the servo hits the stop.
>
> Gary
>
> "Bill Fulmer" <grafix01@cox.net> wrote in message
> news:U3p5h.12984$tH2.6119@newsfe20.lga...
> > "Gary Spence" <whob4me@mindspring.com> wrote in message
> > news:tzn5h.5761$ig4.410@newsread2.news.pas.earthli nk.net...
> > > What is the current draw on the servo while running? Not just the

idel
> > > current.
> > >
> > > Know it will varry with load but a nominal value will be a good start.
> > >
> > > Tried the Futaba site to no avail.
> > >
> > > Thanks for any help
> > >
> > > Gary
> > >

> >
> > Figure on 125ma, but it can easily go as high as 3-4 amps with large

> control
> > surfaces at high speeds...
> >
> > Cheers,
> >
> > Bill
> >
> >
> >
> >

>
>



Old Nov 12, 2006, 08:11 PM
Morgans
Guest
n/a Posts
Re: Futaba S3003 servo current draw?


"Gary Spence" <whob4me@mindspring.com> wrote in message
news:5iN5h.6269$ig4.4881@newsread2.news.pas.earthl ink.net...
> Thanks for the help. Got it (motor only) working on 12 volts. Only using
> the motor with limit switches for an open /closed servo.
>
> Cant get a reading with our meter as it is digital and to slow ro read
> before the servo hits the stop.


Grab hold and don't let it turn for a quick reading. Stall current will be a
good indication of maximum current draw. Startup may be higher, but it is so
short, as to not impact the real world very much.
--
Jim in NC

Old Nov 14, 2006, 08:11 AM
John F. Hughes
Guest
n/a Posts
Re: Futaba S3003 servo current draw?

On 2006-11-14, John F. Hughes <jfNhO@ScPsA.bMrown.edu> wrote:
> On 2006-11-11, Six_O'Clock_High <Six_O'Clock_High@Target_Lock.Guns> wrote:
>>
>> "Bill Fulmer" <grafix01@cox.net> wrote in message
>> news:U3p5h.12984$tH2.6119@newsfe20.lga...
>>> "Gary Spence" <whob4me@mindspring.com> wrote in message
>>> news:tzn5h.5761$ig4.410@newsread2.news.pas.earthli nk.net...
>>>> What is the current draw on the servo while running? Not just the idel
>>>> current.
>>>>
>>>> Know it will varry with load but a nominal value will be a good start.
>>>>
>>>> Tried the Futaba site to no avail.
>>>>
>>>> Thanks for any help
>>>>
>>>> Gary
>>>>
>>>
>>> Figure on 125ma, but it can easily go as high as 3-4 amps with large
>>> control
>>> surfaces at high speeds...
>>>
>>> Cheers,
>>>
>>> Bill
>>>

>>
>> To date the testing we have done tends to indicate STANDARD servos (42 to 50
>> ounce inch range) stall at about 250 to 270 ma. It is reasonable to assume
>> that higher torque servos draw more power.

>
> All of this tells me that servo ratings should be taken with a large
> grain of salt. The S3003 is rated at 57 in-oz of torque, with .16sec /
> 60deg. That means that if it did a full circle, it'd take about 1
> sec. For a one-inch arm, that'd be a distance of pi inches. And
> pulling 57 ounces, we'd get...


Ooops! Make that 2pi inches, so double everything:
>
> 57 pi oz-in/sec
>
> Using my favorite units-conversion program, that's a power of
> about 7.6 Watts. At 6V, that should take about 1.3 amps, *assuming no
> losses*.


Corrected version: 15W, so 2.6amps.

> So if the thing is stalling out at 250ma, it's clearly not
> managing to produce the rated torque. As for current going as high as
> 3-4 amps, that'd mean that the power losses were about a factor of 3,
> and that the servo would be putting out as much heat as a 15W bulb,


Revised: power losses of 40%, 6W heat output. Not too extreme.

> more or less. Those (the ones for sewing machines, for instance) are
> about the same size as a servo, and they get pretty toasty; I have a
> hard time believing that a servo could get that warm without melting
> something inside.
>
> So: stall at 250ma => at most 1/4 of rated torque is being produced
> actually draw 4A => huge inefficiency and LOTS of heat


Revised:

stall at 250ma -> at most 1/8 of rated torque (!)
draw 4A -> modest inefficiency, and some heat.

>
> If I had to bet one way or the other, I'd believe the 250ma
> estimate. Then again, if I were betting my plane, I might want to up
> that to 1.5 amperes just to be a little more on the safe side.


OK. With the new numbers, I'm thinking I'd design for 3A to be safe...

--John (with egg on his face)
Old Nov 14, 2006, 08:11 AM
John F. Hughes
Guest
n/a Posts
Re: Futaba S3003 servo current draw?

On 2006-11-11, Six_O'Clock_High <Six_O'Clock_High@Target_Lock.Guns> wrote:
>
> "Bill Fulmer" <grafix01@cox.net> wrote in message
> news:U3p5h.12984$tH2.6119@newsfe20.lga...
>> "Gary Spence" <whob4me@mindspring.com> wrote in message
>> news:tzn5h.5761$ig4.410@newsread2.news.pas.earthli nk.net...
>>> What is the current draw on the servo while running? Not just the idel
>>> current.
>>>
>>> Know it will varry with load but a nominal value will be a good start.
>>>
>>> Tried the Futaba site to no avail.
>>>
>>> Thanks for any help
>>>
>>> Gary
>>>

>>
>> Figure on 125ma, but it can easily go as high as 3-4 amps with large
>> control
>> surfaces at high speeds...
>>
>> Cheers,
>>
>> Bill
>>

>
> To date the testing we have done tends to indicate STANDARD servos (42 to 50
> ounce inch range) stall at about 250 to 270 ma. It is reasonable to assume
> that higher torque servos draw more power.


All of this tells me that servo ratings should be taken with a large
grain of salt. The S3003 is rated at 57 in-oz of torque, with .16sec /
60deg. That means that if it did a full circle, it'd take about 1
sec. For a one-inch arm, that'd be a distance of pi inches. And
pulling 57 ounces, we'd get...

57 pi oz-in/sec

Using my favorite units-conversion program, that's a power of
about 7.6 Watts. At 6V, that should take about 1.3 amps, *assuming no
losses*. So if the thing is stalling out at 250ma, it's clearly not
managing to produce the rated torque. As for current going as high as
3-4 amps, that'd mean that the power losses were about a factor of 3,
and that the servo would be putting out as much heat as a 15W bulb,
more or less. Those (the ones for sewing machines, for instance) are
about the same size as a servo, and they get pretty toasty; I have a
hard time believing that a servo could get that warm without melting
something inside.

So: stall at 250ma => at most 1/4 of rated torque is being produced
actually draw 4A => huge inefficiency and LOTS of heat

If I had to bet one way or the other, I'd believe the 250ma
estimate. Then again, if I were betting my plane, I might want to up
that to 1.5 amperes just to be a little more on the safe side.

-John



Old Nov 14, 2006, 08:11 AM
funfly3
Guest
n/a Posts
Re: Futaba S3003 servo current draw?

John F. Hughes wrote:
> On 2006-11-14, John F. Hughes <jfNhO@ScPsA.bMrown.edu> wrote:
>> On 2006-11-11, Six_O'Clock_High <Six_O'Clock_High@Target_Lock.Guns> wrote:
>>> "Bill Fulmer" <grafix01@cox.net> wrote in message
>>> news:U3p5h.12984$tH2.6119@newsfe20.lga...
>>>> "Gary Spence" <whob4me@mindspring.com> wrote in message
>>>> news:tzn5h.5761$ig4.410@newsread2.news.pas.earthli nk.net...
>>>>> What is the current draw on the servo while running? Not just the idel
>>>>> current.
>>>>>
>>>>> Know it will varry with load but a nominal value will be a good start.
>>>>>
>>>>> Tried the Futaba site to no avail.
>>>>>
>>>>> Thanks for any help
>>>>>
>>>>> Gary
>>>>>
>>>> Figure on 125ma, but it can easily go as high as 3-4 amps with large
>>>> control
>>>> surfaces at high speeds...
>>>>
>>>> Cheers,
>>>>
>>>> Bill
>>>>
>>> To date the testing we have done tends to indicate STANDARD servos (42 to 50
>>> ounce inch range) stall at about 250 to 270 ma. It is reasonable to assume
>>> that higher torque servos draw more power.

>> All of this tells me that servo ratings should be taken with a large
>> grain of salt. The S3003 is rated at 57 in-oz of torque, with .16sec /
>> 60deg. That means that if it did a full circle, it'd take about 1
>> sec. For a one-inch arm, that'd be a distance of pi inches. And
>> pulling 57 ounces, we'd get...

>
> Ooops! Make that 2pi inches, so double everything:
>> 57 pi oz-in/sec
>>
>> Using my favorite units-conversion program, that's a power of
>> about 7.6 Watts. At 6V, that should take about 1.3 amps, *assuming no
>> losses*.

>
> Corrected version: 15W, so 2.6amps.
>
>> So if the thing is stalling out at 250ma, it's clearly not
>> managing to produce the rated torque. As for current going as high as
>> 3-4 amps, that'd mean that the power losses were about a factor of 3,
>> and that the servo would be putting out as much heat as a 15W bulb,

>
> Revised: power losses of 40%, 6W heat output. Not too extreme.
>
>> more or less. Those (the ones for sewing machines, for instance) are
>> about the same size as a servo, and they get pretty toasty; I have a
>> hard time believing that a servo could get that warm without melting
>> something inside.
>>
>> So: stall at 250ma => at most 1/4 of rated torque is being produced
>> actually draw 4A => huge inefficiency and LOTS of heat

>
> Revised:
>
> stall at 250ma -> at most 1/8 of rated torque (!)
> draw 4A -> modest inefficiency, and some heat.
>
>> If I had to bet one way or the other, I'd believe the 250ma
>> estimate. Then again, if I were betting my plane, I might want to up
>> that to 1.5 amperes just to be a little more on the safe side.

>
> OK. With the new numbers, I'm thinking I'd design for 3A to be safe...
>
> --John (with egg on his face)

but is the speed quoted at zero load or full load I suspect its either
57oz of torque or .16/60deg
not both
Old Nov 14, 2006, 06:11 PM
Tom Minger
Guest
n/a Posts
Re: Futaba S3003 servo current draw?

OK...OK.....OK

I measured two 3003's (used) with virtually identicle results.

Idle current = 26ma
Unloaded transit current = 105ma
Stall current = 430ma

This was with a 4.8 volt nicad pack at 5.1 volts. I have no 6.0 volt packs
with which to test.

I think I read somewhere in this thread that the original question poser was
thinking of using these servos with 12V. That should be interesting, at
least for a few minutes.........


Old Nov 14, 2006, 10:11 PM
Poxy
Guest
n/a Posts
Re: Futaba S3003 servo current draw?


"Tom Minger" <tomminger@volcano.net> wrote in message
news:HuCdnQl_V8mk1MfYnZ2dnUVZ_h2dnZ2d@neonova.net. ..
> OK...OK.....OK
>
> I measured two 3003's (used) with virtually identicle results.
>
> Idle current = 26ma
> Unloaded transit current = 105ma
> Stall current = 430ma
>
> This was with a 4.8 volt nicad pack at 5.1 volts. I have no 6.0 volt packs
> with which to test.


I just tried a 3001 with a 6v pack (note the resistor I was using wasn't
real accurate, so I'd allow 10% error, and the 6v pack might have been a
little flat). I used a digital scope to calculate an average draw - it's
more accurate than a normal meter as it can interpret the current-draw
waveform in a more meaningful manner.
Idle: 14mA
Very lightly loaded transit: 60mA
Stall: 500mA



Old Nov 15, 2006, 04:11 AM
Rick
Guest
n/a Posts
Re: Futaba S3003 servo current draw?

John F. Hughes wrote:
> On 2006-11-14, John F. Hughes <jfNhO@ScPsA.bMrown.edu> wrote:
>> On 2006-11-11, Six_O'Clock_High <Six_O'Clock_High@Target_Lock.Guns> wrote:
>>> "Bill Fulmer" <grafix01@cox.net> wrote in message
>>> news:U3p5h.12984$tH2.6119@newsfe20.lga...
>>>> "Gary Spence" <whob4me@mindspring.com> wrote in message
>>>> news:tzn5h.5761$ig4.410@newsread2.news.pas.earthli nk.net...
>>>>> What is the current draw on the servo while running? Not just the idel
>>>>> current.
>>>>>
>>>>> Know it will varry with load but a nominal value will be a good start.
>>>>>
>>>>> Tried the Futaba site to no avail.
>>>>>
>>>>> Thanks for any help
>>>>>
>>>>> Gary
>>>>>
>>>> Figure on 125ma, but it can easily go as high as 3-4 amps with large
>>>> control
>>>> surfaces at high speeds...
>>>>
>>>> Cheers,
>>>>
>>>> Bill
>>>>
>>> To date the testing we have done tends to indicate STANDARD servos (42 to 50
>>> ounce inch range) stall at about 250 to 270 ma. It is reasonable to assume
>>> that higher torque servos draw more power.

>> All of this tells me that servo ratings should be taken with a large
>> grain of salt. The S3003 is rated at 57 in-oz of torque, with .16sec /
>> 60deg. That means that if it did a full circle, it'd take about 1
>> sec. For a one-inch arm, that'd be a distance of pi inches. And
>> pulling 57 ounces, we'd get...

>
> Ooops! Make that 2pi inches, so double everything:
>> 57 pi oz-in/sec
>>
>> Using my favorite units-conversion program, that's a power of
>> about 7.6 Watts. At 6V, that should take about 1.3 amps, *assuming no
>> losses*.

>
> Corrected version: 15W, so 2.6amps.
>
>> So if the thing is stalling out at 250ma, it's clearly not
>> managing to produce the rated torque. As for current going as high as
>> 3-4 amps, that'd mean that the power losses were about a factor of 3,
>> and that the servo would be putting out as much heat as a 15W bulb,

>
> Revised: power losses of 40%, 6W heat output. Not too extreme.
>
>> more or less. Those (the ones for sewing machines, for instance) are
>> about the same size as a servo, and they get pretty toasty; I have a
>> hard time believing that a servo could get that warm without melting
>> something inside.
>>
>> So: stall at 250ma => at most 1/4 of rated torque is being produced
>> actually draw 4A => huge inefficiency and LOTS of heat

>
> Revised:
>
> stall at 250ma -> at most 1/8 of rated torque (!)
> draw 4A -> modest inefficiency, and some heat.
>
>> If I had to bet one way or the other, I'd believe the 250ma
>> estimate. Then again, if I were betting my plane, I might want to up
>> that to 1.5 amperes just to be a little more on the safe side.

>
> OK. With the new numbers, I'm thinking I'd design for 3A to be safe...
>
> --John (with egg on his face)


Interesting but wouldn't that only be correct if the motor was
directly connected to the servo arm?

--

Rick
--
Old Nov 15, 2006, 08:11 AM
John F. Hughes
Guest
n/a Posts
Re: Futaba S3003 servo current draw?

On 2006-11-15, Rick <rtee@NOSPAMblueyonder.co.uk> wrote:
> John F. Hughes wrote:

<estimates of current deleted>
>
> Interesting but wouldn't that only be correct if the motor was
> directly connected to the servo arm?


Nope: a certain amount of power goes into the servo mechanism; as a
result, it does a certain amount of work over time, and generates some
heat. The "power in" has to equal the "power out" (which is why
"power" is a thing that's worthwhile to define as a physical
term!). If you have a 6-to-1 gear-down, then instead of 57in-oz of
torque, the motor only has to produce 9.5 in-oz of torque...but it
does so over a far greater distance (i.e., it has to make 6 times as
many revolutions). The net power consumption is the same as if you
had a tougher motor, turning slower. (Ignoring all frictional losses,
etc.)

--John
 


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