EC 4 Evil Genius: Project 1 – Lesson 12

Automatic night light

Automatic night light

I finally had some spare cycles this past weekend. This allowed for me to work on 1 of 2 final projects for section one of Electronic Circuits for the Evil Genius. Lesson 12 provides the reader with an opportunity to leverage the knowledge and skills gained thus far. Once the circuit for this project is constructed, it creates an automatic night light that dims in the light and brightens in the dark.

The components used in the circuit include various resistors, a diode, 100k pot, LDR, 5mm LEDs, and a NPN transistor. When attached to a power supply (9v) and with the pot set to around 50k ohms, the LEDs will remain dark/dim in lighted areas and transition to a full glow in a darkened area.

Automatic Night Light

Automatic Night Light

Depending on how much resistance is provided by the pot will determine how much voltage is present in the circuit. Such as, if the pot is set to a low resistance, more voltage is registered, allowing the NPN transistor to be easily activated. Circuit analysis reveals that the LDR is incapable of dumping all of the voltage sent its way.

Although simple in nature, this was an interesting project overall. The knowledge exercised is from the previous sections that dealt with transistor and LDR coverage. This information comes in handy if you attempt to step outside of the suggested components.

For example, the circuit calls for two 5mm LEDs. However, I wanted to use blue LEDs of which require almost double the voltage of red LEDs. Therefore, with the working knowledge of transistors and OHMs Law, I was able to easily determine what type of resistance was necessary to power the two blue LEDs in my circuit.

Automatic Night Light (Testing)

Automatic Night Light (Testing)

This project also required some soldering of components which at least for me is the fun part. The kit associated with the book actually provides you with a ready-to-go PCB. That said, obviously soldering anything worth while is fun; however, experiencing a working circuit when finished is definitely gratifying too.

Lastly, I would recommend keeping the bread boarded circuit as a reference. This way, if you get stuck while putting together the PCB, or if it doesn’t work after the soldering is complete, you have a working physical representation as a reference.

Next up is project #2; post to follow.


One Reply to “EC 4 Evil Genius: Project 1 – Lesson 12”

  1. Algen says:


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    Hope to hear from you soon.



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