10. case 08 servo

10.1. Introduction


  • The servo is a kind of angle servo driver. It is adapted to varying control system. In this case, we are going to use the micro:bit to control rotating of the servo.

10.2. Hardware Connect


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  • Connect circuit as above picture and put 2 AAA batteries into batteries pack.

10.3. Principles of Circuits


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  • The GND of slot on micro:bit is into innards of batteries’ GND to generate the current loop.

10.4. Introduction of Components


Servo

  • A servo is an automatic control system that consists of a DC motor, a reduction gear unit, a potentiometer and a control circuit. Generally, the servo has its the largest rotation angle (For example:180 deg).

  • Our reference point at a 90deg middle position is defined by a signal frequency of 20ms and a pulse width of 1.5ms.

  • The experiment box included a 180° servo. ../../_images/uqmkhZ6.png

Note:You don’t need to think out some complex questions like pulse width because micro:bit Foundation has converted the servo code to block.

- Note: Please note the positive and the negative when you are connecting.

10.5. Software


Step 1

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Step 2

  • Snap the servo write pin and pause block into the forever and set P1 to 0.

  • Pause 2000ms.

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  • Snap the servo write pin again after the first pause block and set P1 to 180.

  • Pause 2000ms.

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Program

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10.6. Result


  • The servo will rotate between 0 deg to 180 deg.

10.7. Think


  • If we want to make a thermometer dial by using the NTC and the servo, how do we design the circuit and the programming?

10.8. Questions


10.9. More Information