Simple Time Delay LED Circuit using Transistor

This article is about Simple Time Delay LED Circuit using Transistor where the LED lit after a short wait; also the circuit needs transistor, capacitor and few resistors for delay.

In addition , the circuit is good for power light, warning light and timing project and it work with 10V DC and fits many electronics.

Circuit Working:

Parts List:

Components	Values	Quantity
Resistors	1k, 68k 1/4 watts	1 each
	Preset 100k	1
Capacitor	Electrolytic 10µF 25V	1
Semiconductors	Transistor BC547	1
	LED 5mm 20mA	1

The circuit uses components such as transistor Q1, capacitor C1, resistors R1 and R2 and a VR1 preset.

First the capacitor charge through VR1 and when charge is high enough, then transistor Q1 is ON and LED1 lights.

Therefore, Delay time = VR1 resistance × C1 capacitance (RC constant).

Formulas with Calculations:

Below are the formulas with calculations for Simple Time Delay LED Circuit using Transistor:

Delay time T = 0.693 × VR1 × C1

Example: 0.693 × 100kΩ × 10µF = 0.693 sec (693ms).

Hence, for more delay, then use bigger preset VR1 or bigger C1 capacitor.

How to Build:

To build a Simple Time Delay LED Circuit using Transistor follow below steps for connection:

• First, take all parts from circuit diagram.
• Next, connect base of Q1 to one end of R2 and other end of R2 goes to one end of VR1 and other end of VR1 go to +10V.
• After that, connect collector of Q1 to one end of R1 and other end of R1 go to +10V.
• Now connect emitter of Q1 to anode of LED1 and cathode of LED1 go to GND.
• Finally, connect positive of C1 to point between R2 and VR1.

Conclusion:

To conclude, this is a Simple Time Delay LED Circuit using Transistor, it is a useful project and VR1 or C1 can adjust the delay.

Also, circuit is easy to build and need only few parts and is good for fun and learning.