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| − | The High Speed Continuous Rotation Servo<ref name=":0">https://www.parallax.com/product/900-00025</ref> from Parallax Inc. is a small, relatively high- |
+ | The High Speed Continuous Rotation Servo<ref name=":0">https://www.parallax.com/product/900-00025</ref> from Parallax Inc. is a small, relatively high-speed servo motor capable of continuous rotation. This motor is particularly suited for being used as a drive motor in small, quick robots. |
== Technical Specifications == |
== Technical Specifications == |
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Latest revision as of 19:00, 30 September 2018
The High Speed Continuous Rotation Servo[1] from Parallax Inc. is a small, relatively high-speed servo motor capable of continuous rotation. This motor is particularly suited for being used as a drive motor in small, quick robots.
Technical Specifications
Gathered from the product page[1] and the Guide PDF[2].
| Supply Voltage | 6 - 8.4VDC, 7.4V typical. |
|---|---|
| Supply Current
(@ 7.4V) |
15mA idle.
130 +/- 50mA at full speed, no load. 1A at stall. |
| Speed | 0 to +/- 150 RPM at 6V.
0 to +/- 180 RPM at 7.4V. |
| Torque
(@ 7.4V) |
22 +/- 11 oz-in.
1.6 +/- 0.8 kg-cm. |
| Dimensions | 2.2 x 0.8 x 1.6 in.
56 x 19 x 41 mm. |
| Weight | 1.5 oz. / 42 g. |
| Operating
Temperature |
14 to 113 °F.
-10 to +45 °C. |
Control[2]
The servo has a standard three-wire hobby servo connecter for delivering power, ground, and control signal. The voltage for a high signal should be in the range of 3.3 to Vservo + 0.2V, with 5V being typical. The voltage for a low signal should be 0V.
[image of basic servo connection diagram]
The servo reads a standard RC PWM signal to set the direction and speed of rotation. A pulse width of ~1.5 ms causes the servo not to rotate, a pulse width of ~1.3 ms causes the servo to rotate full speed clockwise (with the output shaft facing the observer), and a pulse width of ~1.7 ms causes he servo to rotate full speed counterclockwise.
Calibration
The center point of the servo may need to be calibrated to make the servo actually stop when given a 1.5 ms pulse width; this is done by giving the servo a 1.5 ms pulse, and adjusting a small potentiometer exposed through a hole in the case, until the servo stops moving.
The pulse width-to-RPM response of the servo is fairly linear in the range of 1.42 to 1.58 ms (1.5 +/- 0.08 ms), but the response becomes non-linear outside of that range.
[image of servo pulse width-to-RPM response curve]
These nonlinearities will need to be taken into account when designing a software function to set the RPM of the motor using the full range of pulse width values.