Radio Control Hobby Servos: User Manual

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  • Topic: Pulse-width modulation, Servomechanism, Electric motor
  • Pages : 6 (1300 words )
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  • Published : January 7, 2012
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RC Servo C36R, C40R, C55R

User’s Manual

Apr 2009
Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. No representation or warranty is given and no liability is assumed by Cytron Technologies Incorporated with respect to the accuracy or use of such information or infringement of patents or other intellectual property rights arising from such use or otherwise. Use of Cytron Technologies’s products as critical components in life support systems is not authorized except with express written approval by Cytron Technologies. No licenses are conveyed, implicitly or otherwise, under any intellectual property rights.

ROBOT . HEAD to TOE Product User’s Manual – C36R, C40R, C55R

1. Introduction 2. How RC Servo Motor Works 3. Product Specification 4. Wire Connection 5. Connection Between RC Servo and PIC 6. Dimension Drawing 7. Warranty 1 2 3 5 6 7 10

Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved

ROBOT . HEAD to TOE Product User’s Manual – C36R, C40R, C55R

1. INTRODUCTION Radio Control (RC) hobby servos are small actuators designed for remotely operating model vehicles such as cars, airplanes, and boats. Nowadays, RC servos are become more popular in robotics, creating humanoid robot, biologically inspired robot, robotic arm and etc. This is because its’ ability to rotate and maintain and certain location, position or angle according to control pulses from a single wire. Inside a typical RC servo contains a small motor and gearbox to do the work, a potentiometer to measure the position of the output gear, and an electronic circuit that controls the motor to make the output gear move to the desired position. Because all of these components are packaged into a compact, low-cost unit, RC servos are great actuators for robots.

Features: • • • Control position through Pulse Code Modulation Pulse width range: ~ 0.5ms – 2.5ms Come with servo horn and screw accessories

Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved


ROBOT . HEAD to TOE Product User’s Manual – C36R, C40R, C55R

2. HOW RC SERVO MOTOR WORKS Servos are controlled by sending them a pulse of variable width. The signal wire is used to send this pulse. The parameters for this pulse are that it has a minimum pulse, a maximum pulse, and a repetition rate. Given the rotation constraints of the servo, neutral is defined to be the position where the servo has exactly the same amount of potential rotation in the clockwise direction as it does in the counter clockwise direction. It is important to note that different servos will have different constraints on their rotation. 20ms

Pulse Width (0.5ms-2.5ms)

The angle is determined by the duration of a pulse that is applied to the signal wire. This is called Pulse Width Modulation. The servo expects to see a pulse every 20 ms. The length of the pulse will determine how far the motor turns. For example, a 1.5 ms pulse will make the motor turn to the 90 degree position (neutral position). However, the exact correspondence between pulse width and servo varies from one servo manufacturer to another.1.5ms is not necessarily neutral or middle position.

The position pulse must be repeated to instruct the servo to stay in position. When a pulse is sent to a servo that is less than 1.5 ms the servo rotates to a position and holds its output shaft some number of degrees counterclockwise from the neutral point. When the pulse is wider than 1.5 ms the opposite occurs. The minimal width and the maximum width of pulse that will command the servo to turn to a valid position are functions of each servo. Different brands, and even different servos of the same brand, will have different maximum and minimums. Generally the minimum pulse will be about 1 ms wide (some servo is 0.5ms)...
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