Components of a servomotor are: - a DC electric motor, - gears with an output shaft; - position-sensing mechanism; - control circuitry. Robotics and Automation

• Components of a servomotor are: - a DC electric motor,

- gears with an output shaft;

- position-sensing mechanism;

- control circuitry.

Robotics and Automation Careers in Engineering (R.A.C.E project)

Robotics and Automation Careers in Engineering (R.A.C.E project) Servo Motor wiring and plugs

A great advantage of servomotors is that they are very easy to control in comparison with other types of motors (DC, Stepper) that require an H-Bridge or external circuitry. The servo motor has all this circuitry internally. The differences of a servomotors in according to elements from its construction are: - the colours of wires; - the type of spline used. - the type of connector used;The Servo Motors comes with three wires (leads). Two of these wires are to provide ground and positive supply to the servo’ s DC motor. The third wire is for the control signal.


Wires’ signification for a different brands of servomotors are:

Unlike DC motors, reversing the ground and positive supply connections does not change the direction (of rotation) of a servo. This may, in fact, damage the servo motor.


Spline is the place where a servo arm (horn) is connected. It is analogous to the shaft of a common DC motor.

- Hitec splines has 24 teeth;- Futaba splines has 25 teeth. The splines made for one servo type cannot be used with another.

The type of splines for a servomotors are:


The type of plugs for a servomotors are: - Futaba provides a J-type plug with an extra flange for proper connection of the servo. - Hitec has an S-type connector. Futaba connector can be used with a Hitec servo by clipping of the extra flange. Also a Hitec connector can be used with a Futaba servo just by filing off the extra width so that it fits in well.


Inside a Servomotor

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Inside a Servo Motor

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Servo Control - The servo motor can be moved to a desired angular position by sending PWM (pulse width modulated) signals on the control wire. - A pulse of width varying from 1 millisecond to 2 milliseconds in a repeated time frame is sent to the servo for around 50 times in a second. The width of the pulse determines the angular position. When the servo receives a pulse, it can retain the corresponding angular position for next 20 milliseconds. So a pulse in every 20 millisecond time frame must be fed to the servo. - For continuous servo, a pulse of 1 ms moves the servo towards 0°, while a 2 ms wide pulse would take it to 180°; - For standard servo, a pulse of 2 ms moves the servo towards 0°, while a 1 ms wide pulse would take it to 180°; - The pulse width for in between angular positions can be interpolated accordingly. Thus a pulse of width 1.5 milliseconds will shift the servo to 90°. - It must be noted that these values are only the approximations. The actual behavior of the servos differs based on their manufacturer.


Servo Control for standard servo








Servo Control for standard servo,using PBasic programming language


Servo Control for continuous servo








Servo Control for standard servo,using PBasic programming language


Servo control without programming (using a 555 timer circuit)


Servo control without programming (using a 555 timer circuit)

PartTotal Qty.

Description

R1 1 820 Ohm 1/4W Resistor

R2 1 68K 1/4W Resistor



R5 1 1K Linear Taper Pot

C1 1 1uF 16V Electrolytic Capacitor

Q1 1 2N3904 NPN Transistor

U1 1 555 Timer IC

Documents

Components of a servomotor are: - a DC electric motor, - gears with an output shaft; - position-sensing mechanism; - control circuitry. Robotics and Automation