# Case 39：The Mechanical Crab

## Introduction
Build a mechanical crab with the [Nezha Inventor's Kit](https://shop.elecfreaks.com/products/elecfreaks-micro-bit-nezha-48-in-1-inventors-kit-without-micro-bit-board?_pos=2&_sid=ed1b6fbd2&_ss=r). 

![](./images/39_1.png)

## Quick to Start
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### Materials Required

[Nezha Inventor's Kit](https://shop.elecfreaks.com/products/elecfreaks-micro-bit-nezha-48-in-1-inventors-kit-without-micro-bit-board?_pos=2&_sid=ed1b6fbd2&_ss=r)

### Assembly
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Components List

![](./images/neza-inventor-s-kit-case-39-02.png)

Build it as the assembly steps suggest: 

![](./images/neza-inventor-s-kit-step-39-01.png)

![](./images/neza-inventor-s-kit-step-39-02.png)

![](./images/neza-inventor-s-kit-step-39-03.png)

![](./images/neza-inventor-s-kit-step-39-04.png)

![](./images/neza-inventor-s-kit-step-39-05.png)

![](./images/neza-inventor-s-kit-step-39-06.png)

![](./images/neza-inventor-s-kit-step-39-07.png)

![](./images/neza-inventor-s-kit-step-39-08.png)

![](./images/neza-inventor-s-kit-step-39-09.png)

![](./images/neza-inventor-s-kit-step-39-10.png)

![](./images/neza-inventor-s-kit-step-39-11.png)

![](./images/neza-inventor-s-kit-step-39-12.png)

![](./images/neza-inventor-s-kit-step-39-13.png)

![](./images/neza-inventor-s-kit-step-39-14.png)

![](./images/neza-inventor-s-kit-step-39-15.png)

![](./images/neza-inventor-s-kit-step-39-16.png)

![](./images/neza-inventor-s-kit-step-39-17.png)

![](./images/neza-inventor-s-kit-step-39-18.png)

![](./images/neza-inventor-s-kit-step-39-19.png)

![](./images/neza-inventor-s-kit-step-39-20.png)

![](./images/neza-inventor-s-kit-step-39-21.png)

![](./images/neza-inventor-s-kit-step-39-22.png)

![](./images/neza-inventor-s-kit-step-39-23.png)

![](./images/neza-inventor-s-kit-step-39-24.png)

![](./images/neza-inventor-s-kit-step-39-25.png)

![](./images/neza-inventor-s-kit-step-39-26.png)

![](./images/neza-inventor-s-kit-step-39-27.png)

We can see that the construction is completed as shown in the following figure:

![](./images/neza-inventor-s-kit-case-39-01.png)

### Connection Diagram

Connect the [Ultrasonic Sensor](https://shop.elecfreaks.com/products/elecfreaks-planetx-ultrasonic-sensor?_pos=1&_sid=d432fa273&_ss=r) to J1 and the [motor ](https://shop.elecfreaks.com/products/elecfreaks-high-speed-building-blocks-motor?_pos=4&_sid=bfad50d7f&_ss=r)to M1 on [Nezha Breakout Board](https://shop.elecfreaks.com/products/elecfreaks-nezha-breakout-board?_pos=1&_sid=c41e367c3&_ss=r).

![](./images/neza-inventor-s-kit-case-39-03.png)


## MakeCode Programming
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### Step 1
Click "Advanced" in the MakeCode drawer to see more choices.

![](./images/neza-inventor-s-kit-case-37-04.png)

For programming the [Ultrasonic Sensor](https://www.elecfreaks.com/planetx-ultrasonic.html), we need to add a package. Search with "PlanetX" in the dialogue box and click to download it. 

![](./images/neza-inventor-s-kit-case-37-05.png)

For programming [Nezha Breakout Board](https://shop.elecfreaks.com/products/elecfreaks-nezha-breakout-board?_pos=1&_sid=00432325a&_ss=rl), we need to add a package. Search with "Nezha" in the dialogue box and click to download it. 

![](./images/neza-inventor-s-kit-case-37-06.png)

*Notice*: If you met a tip indicating that some codebases would be deleted due to incompatibility, you may continue as the tips say or create a new project in the menu. 

### Step 2

### Code as the picture suggests

![](./images/neza-inventor-s-kit-case-39-07.png)


### Reference
Link: [https://makecode.microbit.org/_09MCJLLdTYcr](https://makecode.microbit.org/_09MCJLLdTYcr)

You may also download it directly: 

<div style="position:relative;height:0;padding-bottom:70%;overflow:hidden;"><iframe style="position:absolute;top:0;left:0;width:100%;height:100%;" src="https://makecode.microbit.org/#pub:_09MCJLLdTYcr" frameborder="0" sandbox="allow-popups allow-forms allow-scripts allow-same-origin"></iframe></div>  

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### Result
After powering on, if the crab sees an approaching object ahead, it will crawl towards sideways.

![](./images/39_39.gif)