Handson Technology
Data Specs
775 Ball Bearing DC Motor
Ball bearing DC motor with built-in cooling fan. High torque with wide operating voltage
6~20Vdc. Suitable for motor tools application and DIY projects.
SKU: FAM1011
Specifications:
Motor Type: 775.
Operating Voltage: 6~20Vdc. (Nominal 12Vdc)
No Load Speed: 12,000 RPM @ 12V.
Rated current: 1.2A @ 12V.
Stall Torque: 79Ncm @ 14.4V.
Cooling Fan: Internal
Overall Size: 98x42mm.
Shaft: Full Round Type Ø5mm.
Mounting Screw Size: M4.
Weight: 350g.
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Mechanical Dimension:
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Application Examples:
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Application Note: Useful Motor/Torque Equations
Force (Newtons)
F=mxa
m = mass (kg)
a = acceleration (m/s2)
Motor Torque (Newton-meters)
T=Fxd
F = force (Newtons)
d = moment arm (meters)
Power (Watts)
P=IxV
I = current (amps)
V = voltage (volts)
P=Txω
T = torque (Newton-meters)
ω = angular velocity (radian/second)
Unit Conversions
Length (1 in = 0.0254 m)
Velocity (1 RPM = 0.105 rad/sec)
Torque (1 in-lb = 0.112985 N-m)
Power (1 HP = 745.7 W)
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Example 1
Determine if the following motor can be used to lift a 5-kg load using a 0.5-m lever arm.
Merkle-Korff Gearmotor specifications
Stall Torque = 40 in-lb
Stall Current = 3.5 amps
Solution
Convert Stall Torque from in-lb to N-m
1 in-lb = 0.112985 N-m
40 in-lb = 40 x 0.112985 N-m = 4.5194 N-m
Calculate the Force required to lift the 5-kg load
F = m x a = 5 kg x 9.81 m/s2 = 49.05 N
Calculate the Torque required to lift the Force with the lever arm
T = F x d = 49.05 N x 0.5 m = 24.525 N-m
We cannot perform the lift with this set-up, because the stall torque is smaller than the
torque required for the lift. We must either shorten the length of the lever arm, or we must
choose another motor with a higher stall torque to perform this operation.
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Example 2
Using the same motor as in Example 1 with a 12-V power supply:
a) Calculate the power used by the motor to rotate a 5-kg load at 50 RPM using a 3-inch lever arm.
b) Calculate the current draw from the battery to perform this operation.
Solution
Convert inches to meters:
1 in = 0.0254 m
3 in = 0.0762 m
Calculate the Force required to lift the 5-kg load:
F = m x a = 5 kg x 9.81 m/s2 = 49.05 N
Calculate the Torque required for this operation:
T = F x d = 49.05 N x 0.0762 m = 3.738 N-m
Note- This toque is lower than the motor’s stall torque, so this operation is possible using the
specified motor, mass, and lever arm
Convert RPM to radians/second:
1 RPM x 2π rad/rev x 1 min/60 sec = 0.105 rad/sec
ω = 50 rev/min x 0.105 rad/sec/RPM = 5.25 rad/sec
Calculate the Power required for this operation:
P = T x ω = 3.738 N-m x 5.25 rad/sec = 19.622 W
Calculate the Current draw from the battery (use the supply voltage in this calculation):
I = P/V = 19.622 W/12 V = 1.635 Amps
Note- This current is smaller than the maximum allowable current draw of the motor.
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Example 3
Determine the motor torque necessary to power the robot drive wheels.
Solution
The following approach is merely one way to solve this problem. Several exist.
Assume the robot will be powered by two powered drive wheels and supported by two freely rotating caster
wheels. Robot weight is denoted by W and for this simple example we’ll assume the weight is distributed
evenly over all 4 wheels, as shown in Figure 1 below.
Thinking logically about the problem, we could model the robot as having 4 of the identical caster wheels
(Figure 2) and the force required to propel the robot is simply the force needed to start the robot moving
(this could be measured empirically with a force scale). The problem is we haven’t yet built the robot so
testing it in this manner is not an option. We need to calculate the force (and hence motor torque) required to
move the robot before we build anything.
Looking closer at the caster wheel we can see the actual friction that must be overcome to put the robot in
motion. Fw is the friction force between the wheel and the floor and Fa is the friction force between the
wheel and the axle. Tw and Ta are the respective torques between the wheel and floor and the wheel and
axle.
Fa = W/2 * μa
Ta = Fa * Ra
Fw = W/2 * μw
Tw = Fw * Rw
Tw is the maximum torque the wheel can transmit to the ground before it slips.
Our goal is to find a realistic range for Tm, the motor torque.
As calculated above, Tw would be the maximum amount of torque the motor could transfer to the ground
before the wheel begins to slip (ie Tm, max).
Typically, we desire μw > μa, so the wheel does not slip/slide across the floor, but rather rolls. We can easily
look up the μa value for the axle/wheel materials in contact. Knowing μa and the weight of the vehicle, Fa
can be computed. This is the minimum amount of force we would have to provide at the wheel/axle interface
to overcome the friction between the two. To relate the computed axle force Fa to the minimum amount of
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wheel torque required to move the robot, we would use the “virtual radius” of the wheel/axle combination,
which is computed as follows:
Rv = Rw – Ra
This is the fictitious radius about which Fa would act to rotate the wheel about the tangent point in contact
with the ground at any instant, as shown in Figure 4 below.
Therefore our equation for the minimum amount of torque the motor must transfer to the ground before the
wheel begins to roll (thus causing the robot to move) would be:
Tm (min = Fa * Rv = Fa * (Rw – Ra)
In summation, Tm, min ≤ Tm ≤ Tm, max or alternatively, Fa * (Rw – Ra) ≤ Tm ≤ Fw * Rw
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Motors, Fans and Accessories Selection
40x40x10 mm DC Brushless Cooling Fan GA12-N20 Geared Mini DC Motor
Ultra quiet powerful brushless DC fan, quiet sleeve- This is a DC Mini Metal Gear
bearing design. Specialized Motor, ideal for making
design, professional made, robots. Light weight, high
stable performance. torque and low RPM. Fine
Operating Temperature: -10 craftsmanship, durable, not
C to +60C. Long Life easy to wear. Widely used on
Expectancy. boat, model car, robotic, home appliances, linear motion
control.
EMH-1071 GDT4010S12B RM 6.50 EMH-1176 GA12-N20 RM 18.50
30x30x10 mm DC Brushless Cooling Fan Nema23 Bipolar/Unipolar Stepper Motor 1.0A
Ultra quiet powerful brushless DC fan, quiet sleeve- A stepper motor to satisfy all
baring design. Specialized your 3D-Printer, robotics,
design, professional made, Linear Motion projects needs!
stable performance. This 6-wire uni-polar/bipolar
Operating Temperature: -10 stepper motor has 1.8° per step
C to +60C. Long Life for smooth motion and a nice
Expectancy. holding torque.
EMH-1070 GDT3010S12B RM 7.50 EMH-1179 23HS2610 RM 110.00
1.2A Nema 17 Stepper Motor 1.7A Nema 17 Stepper Motor
A stepper motor to satisfy all A stepper motor to satisfy all your 3D-Printer, robotics,
your 3D-Printer, robotics, Linear Motion projects needs!
Linear Motion projects needs! This 4-wire bipolar stepper has
This 4-wire bipolar stepper has 1.8° per step for smooth motion
1.8° per step for smooth and a nice holding torque.
motion and a nice holding
torque.
EMH-1016 42HS40-1204D RM 44.50 EMH-1181 17HS-4401SD RM 47.00
SG90 Tower Pro Gear Micro Servo Motor Nema-17 Planetary Geared Stepper Motor
Tiny and lightweight with high output power. Servo can This high precision NEMA17 Stepper motor has an
rotate approximately 180 integrated Planetary
degrees (90 in each Gearbox with 1:5.18 gear
direction). Good for ratio, the resolution can
beginners who want to reach 0.35°step angle.
make stuff move without
building a motor controller
with feedback & gear box.
EMH-1173 42BYGP40P RM 185.00
EMH-1140 TPSG90S RM 7.40
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Web Resources:
68mm High Grip Rubber Wheel for Robotics Car
Hex Motor Shaft Coupler for Robotic Wheel
Right Angle Bracket for JGB37 Gear Motor
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