# 3.21 Window Close In Dark

## 3.21.1 Overview

In this project, we program to make the window automatically close when getting dark. So the photoresistor is required to sense the ambient light. We set a threshold for the resistor. When ambient light value is lower than the threshold, the servo closes the window.

## 3.21.2 Code Flow

![](./media/t156.png)

## 3.21.3 Code Blocks

Blocks in ![](./media/operators.png):

1. ![t158](./media/t158.png) is used to compare two values. If the first one is greater than the second one, it returns true.
2. ![t157](./media/t157.png) is also used to compare two values. If the first one is smaller than the second one, it returns true.
3. ![t163](./media/t163.png) determines whether the conditions on both sides are met. If yes, it outputs True; if one of the conditions is not met, it outputs False.

For more details, please visit [Blocks Reference | MicroBlocks Wiki](https://wiki.microblocks.fun/en/reference_manual#operators)

## 3.21.4 Test Code

You can manually build blocks, or directly open the code file we provide: `3-21-Window Close In Dark.ubp`. If you have any questions about how to open code files or upload code, please back to `1.9 Upload Code`.

**Build code blocks:**

1. In ![](./media/control.png), drag ![](./media/t1.png) and ![](./media/t2.png) to the script area, and stack them together.

![t34](./media/t34.png)

2. Check whether the value of the photoresistor is less than 500. If it is, the servo rotates to 180°; if not, the servo rotates to 0°.

![t159](./media/t159.png)

## 3.21.5 Test Result

Connect the coding box to the MicroBlocks via USB or Bluetooth, and click ![t59](./media/t59.png) to upload the code to the coding box. Cover the photoresistor to lower its analog value under 500 and the servo will rotate to 180°. If the analog value exceeds 500, the servo will rotate to 0°.