# case 04 trimpot 

## Introduction ##

The trimpot is a common pressure regulation component. In this case, we are going to read output voltage of the trimpot and show the voltage with a bar graph in 5*5 LED allay of micro:bit. 


## Products Link

[ELECFREAKS Experiment Box Kit](https://shop.elecfreaks.com/products/elecfreaks-experiment-box-kit-without-micro-bit-board?_pos=1&_sid=ac099db2f&_ss=r)

## Hardware Connect ##


![](./images/LMsve7H.png)
 Connect circuit as above picture and put 2 AAA batteries to the batteries pack.

## Principles of Circuits ##

![](./images/VFmWZkG.png)

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


## Introduction of Components ##

### Trimpot ###
 The trimpot is a pressure regulation component which included a resistance and a slide system. The resistance measured varies based on the movement of a knob or slider between the middle terminal and outer terminals. 
 There is a 10KΩ trimpot on the experiment box. When it turns left, it will be 0Ω; when it turns right, it will be 10KΩ.

![](./images/jHZQhOu.png)

## Software

### Step 1

 Click [makecode https://makecode.microbit.org/#](https://makecode.microbit.org/#)。

 Click on "New Project" and set a new Project.

![](./images/t34k5Zb.png)

### Step 2

![](./images/3Ekc31T.png)

 Snap plot bar graph into the forever to show a bar graph.（A bar graph is a kind of table which can show number by diffrent lengths.）

 "analog read pin" is to read a signal of a pin.（0~1023）

### Program

 Program link：[https://makecode.microbit.org/_VewWgwe8HVT1](https://makecode.microbit.org/_VewWgwe8HVT1)

 You also could directly download program by visiting website as below:

<div style="position:relative;height:0;paddingbottom:70%;overflow:hidden;"><iframe style="position:absolute;top:0;left:0;width:100%;height:100%;" src="https://makecode.microbit.org/#pub:_VewWgwe8HVT1" frameborder="0" sandbox="allowpopups allowforms allowscripts allowsameorigin"></iframe></div>  


## Result

 Rotate the trimpot, the height of the bar graph will change.

![](./images/WDagGas.gif)

## think

 Is the trimpot could be a fixed resistance？

## Questions



## More Information