***Question***

> PIR motion sensor always on and stays on. Why?

***Answer***

Well, there are 101 possible reasons:

> 1.  Sensor sensitivity set too high.
> 
> 2.  Sensor time delay set too low.
> 
> 3.  ...
> 
> 4. ...
> 
> 5. You forgot to read the user guide.

***Suggestion*** 

Use a bowl.

[![sensor spec][1]][1]

[![sensor test][2]][2]

***References***

[Introduction to HC-SR501 A complete step by step tutorial on Introduction to HC-SR501][3]

[TaoBao HC-SR501 PIR Sensor Module - ¥3.23][4]


[TaoBao DC 12V Water Proof Smart PIR Sensor Module With Switch - ¥12.80][5]



[TaoBao AM312 PIR Sensor ¥5.28][6]


  [1]: https://i.sstatic.net/4JNSH.jpg
  [2]: https://i.sstatic.net/Aqo7y.jpg
  [3]: https://www.theengineeringprojects.com/2019/01/introduction-to-hc-sr501.html
  [4]: https://item.taobao.com/item.htm?spm=a1z1r.7974869.0.0.269c3ad43nX1A5&id=563241533003
  [5]: https://item.taobao.com/item.htm?spm=a1z1r.7974869.0.0.269c3ad43nX1A5&id=589366692547
  [6]: https://item.taobao.com/item.htm?spm=a1z1r.7974869.0.0.269c3ad43nX1A5&id=574891236513