How to quickly learn transistor and LDR circuits?
In this post, I am going to show you how easy learning.
My son wants to build a simple automatic flasher. It is special. Why?
It will be light in the dark. This circuit uses 5 parts only and cheap.
He likes to play LEGO very much. So builds the Lighthouse tower with LEGO block.
It is not important for you. Even more importantly.
I hope this helps you improve understanding it works. For example, the voltage divider circuit, resistor works, and more.
Ready to get started?
How circuit works
As Figure 1, this circuit uses the simple transistor driver for flashing LED.
He uses the Multicolor Flashing LED for LED1
How to build
He assembles them on a small breadboard as Figure 2. When applying the 2.4V power supply to the circuit. The small current flow through to R-10K to the base lead of transistor Q1- 2N3904, makes large current flow through the collector to emitter lead, and LED1 will glow up. As Figure 3.
Figure 2 assemble the circuit on a breadboard
Figure 3 LED glow up
Then, he put LDR into the 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 the base of transistor so it not work. LED will go out.
And after, he turns off the lamp. The resistance of LDR is high, so the R1’s current can flow through the base of the transistor again. It makes large current from collector flow to the emitter of the 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
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