1. Hitec HS 303: Robotic Servo Motor
Contact Info
David Kusinsky
AIM: SparusX
Hitec HS 303: Robotic Servo Motor
Uses
Pulse Width Modulation
EE/CE Description
Mechanical Description
Test Circuit
Jameco Part No: $19.95

2. Image courtesy of battlebots.com
Uses
Hobbyists (model airplanes, cool Lego toys, etc.)
Robotics!
Image courtesy of battlebots.com

3. Pulse Width Modulation
Duty Cycle => Proportion of time that a device is operated vs. idle.
In this case, duty cycle is: time ‘1’ / interval
Basic Idea of PWM: Keep frequency constant, and vary the duty cycle.
Ex. 75% duty cycle

4. EE/CE Description
Servo functions through a pulse width modulated control input. (50 Hz square wave)
Duration of logic ‘1’ (duty cycle) determines angle of servo axis.
Varies by manufacturer: HS ms – 0 degrees ms – Center ms – 90 degrees
Potentiometer (POT) connected to servo axis allows control circuitry to monitor servo’s position.

5. Mechanical Description
Control Circuitry, Motor, Gears, and Case
Three Wires: Red ( VDC), Black (0 VDC), Yellow (Control Signal)
High Torque vs. Size ( VDC, VDC)
60 degrees ( VDC, VDC)

6. Test Circuit 555D => ST NE555N 555 Timer R1 & R2 => 10k POT
C1 => Filter Cap.
C2 => Trigger Cap.