We need the following components:
one LTR-4206E phototransistor
one lithium CR2032 battery (3 V)
2N3904 transistor
1K resistor
Photos of these components:
![](https://i.washerhouse.com/_nw/1/04450896.jpg)
![](https://i.washerhouse.com/_nw/1/12722920.jpg)
Progress:
First, take a Transistor and a resistor and solder them as shown in the figure:
![](https://i.washerhouse.com/_nw/1/68361814.jpg)
![](https://i.washerhouse.com/_nw/1/48180845.jpg)
Next, we solder a phototransistor to this structure:
![](https://i.washerhouse.com/_nw/1/64124284.jpg)
![](https://i.washerhouse.com/_nw/1/75634733.jpg)
Next we will attach Light-emitting diode :
![](https://i.washerhouse.com/_nw/1/43645683.jpg)
And then the power source:
![](https://i.washerhouse.com/_nw/1/59836787.jpg)
![](https://i.washerhouse.com/_nw/1/53946449.jpg)
And now let's see what we got:
![](https://i.washerhouse.com/_nw/1/72270518.jpg)
![](https://i.washerhouse.com/_nw/1/90476228.jpg)
This light will turn on when it gets dark
![](https://i.washerhouse.com/_nw/1/35480377.jpg)