Why do servos use so much power?

Hello,
I was looking for a servo, and I was just curious to notice that a micro servo, with a very small motor,uses about 4.8-6V of power. Just out of curiosity, why is this. I've seen larger and more powerful dc motors go for 3v, 6v...but the one in a micro servo is tiny.
Thanks.

Voltage alone is not a sign of power.
Voltage x current draw is power, Pwatts = Icurrent x Vvolts.

The 4.8 to 6V tells you something about the onboard circuitry that controls the motor.
It is likely designed to be compatible with 5V control systems (such as Arduino) while being powered from 4 NiCad batteries (4.8V) up to 4AA batteries (6V).

Why is the sky blue?

4.8-6V of power

You mean voltage not power.

4.8-6V, maybe for battery use.

Fair enough...thanks!

As others say, voltage is not power.
What voltage servo/motor were you expecting?

Jack

The question was, "a very small motor uses about 4.8-6V of power. Just out of curiosity, why is this"?

I checked a book called "Linear Electric Actuators and Generators" by I. Boldea and S. Nasar on page 37, Equation 2.1 and it shows that the Force is important and it causes Work to be done by current.
Equation 2.1, simplified:
F = dW/dx = 1/2(i*i)(dL/dx) Newtons

L is inductance
F is Force
W is Work
x is distance
d is a symbol from calculus
Work is Heat and Energy, not Power
Power is Energy per second

Conclusion


The 6 volt motor you are concerned for may have a spec to fit into 6 volt systems, resulting in better sales. Motors use a lot of energy compared to a NAND gate because the efficiency of inductors is limited by the laws of nature. In practice, the induction motors work best with small gaps. How small? dx

vek11:
Hello,
I was looking for a servo, and I was just curious to notice that a micro servo, with a very small motor,uses about 4.8-6V of power. Just out of curiosity, why is this. I've seen larger and more powerful dc motors go for 3v, 6v...but the one in a micro servo is tiny.
Thanks.

Would you be happier if it used 240volts? and only a few milliamps?

Watts is your power rating (voltage * amps = watts)

eg
10v * 1amp = 10watts
100v * 0.1amp = 10watts

Comprende... reminds me of the time a guy once told me he's using probably around 100volts of his 240volt power supply!

"Yeah, 220, 221 , whatever it takes." 8)

AmbiLobe:
Equation 2.1, simplified:
F = dW/dx = 1/2(i*i)(dL/dx) Newtons

Huh? That's totally bogus. dL/dx is zero, that differential should be over the entire expression for energy, but that's
even more broken because its the expression for energy in an inductor where the energy depends on current and
x (displacement) is not relevant.

The laws for motion of a conductor in a magnetic field are

F = B I l
V = B l v

F, force in newtons
B, mag flux density in tesla
I, current in amps
l, length of conductor in metres
V, (back) emf in volts
v, velocity in m/s

(where the motion, the current and the mag field are all mutually at right angles.)

In a simple permanent magnet DC motor (with 100% efficiency) the values of B and l are part of the motor's geometry and
motion is (usually) in a circle so we replace force by torque, velocity by angular velocity, and get

T = K I
V = K w

T, torque in N-m
K = B l, a constant of the motor in N-m/A (or V-s/rad)
w, angular velocity in rad/s

Power = V I = T w

In a real motor the mechanical power is less than the electrical power due to losses, but the simple model
isn't too unreasonable.

CrossRoads:
"Yeah, 220, 221 , whatever it takes." 8)

A Mr. Mom fan?

That's always a great line! Micheal Keaton was so good in a lot of movies.

He was my favorite Batman, by far.

He's been sort of off the screen for a while doing voices, but I hear he'll be in 2 or 3 movies over the next year or so. It will be good to see him back.

CrossRoads:
That's always a great line! Micheal Keaton was so good in a lot of movies.

One of my favorite actors, does comedy as well as straight roles. First saw him in 'night shift' and who can forget 'beetlejuice'. Saw him once in a Montana roadside restaurant wearing a fly fishing outfit where we stopped for lunch, he was probably on vacation, but I didn't bug him.

Lefty

Servo motors such as this are designed for radio controlled models. Historically, when those servos were originally designed, RC receivers ran from four AA cells, 6V if alkaline, 4.8V if NiCd. Hence, the servos were designed for that voltage.

In fact, most analog servos seem to all be using updated clones of the first IC designed to run servos such as these. Improvements, but same basic operation.

The power vs voltage thing has been answered, so I won't bother addressing that.

Imagine life if Edison had gotten his way....

You only get electric if you lived within 15 miles of the power station, the cables to deliver it were stupidly thick in order to prevent them burning out to carry the load, we have so much to thank Mr Tesla you have no idea...

On the upside, 12-15vdc would be amazingly perfect connect the car battery to it for example, projects you'd not need an expensive step down transformer to deliver 100 amps at 12v, i bet some interesting things could be done if Thomas Edison got his way...

Um... what?

cjdelphi:
Imagine life if Edison had gotten his way....

You only get electric if you lived within 15 miles of the power station, the cables to deliver it were stupidly thick in order to prevent them burning out to carry the load, we have so much to thank Mr Tesla you have no idea...