This is power battery saver circuit using an IC-555 timer. The lamp is controlled with a PWM mode by adjusting of potentiometer VR1. And, PNP power transistor drives a lamp.
Sometimes a light bulbs or lamp is too brightness. It is shorter lifespan and wastes too much electricity. You need just enough light only. First, you may use a variable resistor in sires. To adjust the brightness. But it does not work. Because it uses a high power.
There a lot of ways to fix the problem. This is on another way you may like it. It can save the power of a battery. The brightness of the light bulb is equal to the amount of power supplied to the battery.
Power saver principle
Usually, we will feed a normal voltage to the lamp. But a high power loss too much. We need to fix the problem by add PWM circuit control.
It will change a DC voltage, 9V. To become the DC pulse. Then, adjust a width of the DC pulse. To control the power to the lamp. Look at Figure below, you will clear better.
In circuit use the 555 timer IC to connected as astable multivibrator circuit. Which it will generate a frequency DC Pulse to output. You can adjust the duty cycle or pulse wide by VR1. The diode D1 to D3 is used to protect incorrect power supply connection.
Parts you will need
IC1: NE555 Timer IC
D1,D2,D4: 1N4148, 75V 150mA Diodes
D3: 1N4007, 1000V 1A Diode
1/4W Resistors tolerance: 5%
R3: 220 ohms
C1: 33uF 16V, Electrolytic capacitor
C2: 0.01uF 50V, Ceramic
Q1: BD140, 80V 1.5A PNP Transistor
VR1: 1M potentiometer
L1: 7.2V 550mA Lamp
B1: 9V battery
S1: on-off switch
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