Lego automatic LED flasher light

Today myson want to build the simple automatic flasher circuit. It is special that it will be light on dark. This circuit use 5 parts only and cheap. He like to play LEGO very much so builds Lighthouse tower by LEGO block.

How circuit works
As Figure 1, this circuit use the simple transistor driver for flashing LED.

He uses the Multi color Flashing LED for LED1

He assemble them on small breadboard as Figure 2. When apply the 2.4V power supply to the circuit. The small current flow through to R-10K to base lead of transistor Q1- 2N3904, makes large current flow through collector to emitter lead, and LED1 will glow up. As Figure 3.


Assemble the circuit on breadboard
Figure 2 assemble the circuit on breadboard

LED glow up
Figure 3 LED glow up

Then, he put LDR into circuit as Figure 4. When the light to LDR, its resistance is low. So the R1’s current flow through to LDR instead. It makes no current to base of transistor so it not work. LED will go out.
And after, he turn off the lamp. The resistance of LDR is high, so the R1’s current can flow through the base of transistor again. It make large current from collector flow to emitter of transistor so LED glow up or flashing light.


Figure 4 Lego automatic LED flasher light circuit

As video below he builds and make them!

It is first video that he speak English

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Close Menu