Obstacle Detection Circuit Using BC547 with UTSource

Introduction

Today, we are going to build an obstacle detection circuit using two transistors. The detection device of the circuit is an IR LED. For this, we need two transistors, one NPN transistor, and one PNP transistor. We are going to use the BC547 NPN transistor and the BC557 transistor. Both the BC547 and BC557 have the same pinout, and you can see its pinout in the below image:

Circuit Diagram

This is the basic circuit diagram of the obstacle detection circuit. In this circuit, one IR LED is always on. The other IR LED is connected to the base pin of the BC547, since this IR LED is acting as the detector.

Steps to follow:

Step 1: Arrange the components.

Step 2: Solder one IR LED to the emitter pin of the BC547 transistor.

Step 3: Solder the other IR LED to the base pin of the BC547 transistor.

Step 4: Solder the 100Ω resistor to the remaining pins of the IR LEDs.

Step 5: Solder the base pin of the BC557 transistor to the collector pin of the BC547 transistor.

Step 6: Solder the normal LED as shown in the circuit diagram.

Step 7: Solder the 220Ω resistor as shown in the circuit diagram.

Step 8: The circuit is now ready to connect to power as shown in the circuit diagram in order to test it.

How it works:

When the detector IR LED is detected, the reflected IR light from the object will trigger a small current that will flow through the detector IR LED. This will trigger the BC547 transistor and it will also cause the BC557 to trigger, hence the LED will turn on.

Conclusion

You can use this circuit to build various projects such as automatic lamps which turns on when a person comes near to the light.

Enjoy! Contact us for any inquiries!