A circuit that controls how bright a lamp shines using pulse width modulation PWM is super useful for anyone who wants to adjust the light of an incandescent lamp to their liking.
This PWM Based Lamp Brightness Controller Circuit uses a 555 timer chip set up as an astable multivibrator which helps manage how bright a low power lamp gets.
With the PWM method the circuit cleverly controls the power going to the lamp making it easy to change how bright it is.
Plus, this cool circuit runs on a 6V battery, so it is practical and works well for different lighting needs.
Circuit Working:
Parts List:
| Component | Value/Type | Quantity | Notes |
|---|---|---|---|
| Resistors (1/4W) | |||
| Resistor | 10k | 1 | |
| Resistor | 47k | 1 | |
| Resistor | 1.5k | 1 | |
| Potentiometer | 470k | 1 | |
| Capacitors | |||
| Ceramic Capacitor | 22nF | 1 | |
| Electrolytic Capacitor | 100µF 25V | 1 | |
| Semiconductors | |||
| IC | 555 Timer | 1 | |
| Transistor | BD681 | 1 | |
| Diode | 1N4148 | 2 | |
| Other Components | |||
| Switch | ON/OFF | 1 | |
| Lamp | Incandescent 6V / 200 mA | 1 | |
| Battery | 6V | 1 |
In this post the circuit uses an IC 555 timer chip that has been set up to work in astable mode, which helps create a pulse-width modulation PWM signal.
This PWM signal is important because it controls how bright the incandescent lamp shines, as it is connected to the circuit.
The timing parts that affect how fast the IC 555 chip oscillates include resistors R1, R2 and VR1 along with capacitor C1.
Diodes D1 and D2 are also included to create an uneven duty cycle allowing the brightness to be changed by adjusting the resistance of R2.
The PWM output from pin 3 of the chip drives the power transistor Q1 controls the current going through the lamp.
Moreover, capacitor C2 plays a key role in keeping the power supply stable making sure the circuit works well.
By changing the resistance of R2 you can control how bright the lamp gets since this change directly affects the duty cycle of the PWM signal.
Formulas with Calculations:
The formulas with calculations for PWM Based Lamp Brightness Controller Circuit is mentioned below:
For an astable 555 timer circuit with diodes for separate charge and discharge paths, the ON and OFF times are calculated as follows:
Charge time (TON):
TON = 0.693 × R1 × C1
Discharge time (TOFF):
TOFF = 0.693 × R2 × C1
Frequency of oscillation:
f = 1 / (TON + TOFF)
Duty cycle:
Duty Cycle (%) = (TON / (TON + TOFF)) × 100
Adjusting R2 changes TOFF thereby altering the duty cycle and adjusting the brightness of the lamp.
How to Build:
To build a PWM Based Lamp Brightness Controller Circuit following steps are required for connections of the circuit.
- Assemble all the components mentioned in the above circuit diagram
- Connect pin 1 of ICI 555 to GND of the circuit
- Connect pin 2 and pin 6 of IC1
- Connect pin 3 of IC1 to base of transistor Q1 through resistor R3
- Connect pin 4 and pin 8 of IC1 to positive supply of the circuit
- Connect a resistor R1 from pin 7 of IC1 and positive suplly.
- Connect capacitor C1 from pin 2 of IC1 and GND
- Connect diodes D1 and D2 in series from pin 7 of IC1.
- Connect the cathode of diode D1 to one end of pot VR1 and anode of diode D1 to pin 7 of IC1
- Connect cathode of diode D2 to pin 7 of IC1 and anode of diode D2 to one end of resistor R2 and other end of R2 connect to VR1 pot.
- Connect the emitter of transistor Q1 to GND of the circuit
- Connect the collector of transistor Q1 to one end of incandescent lamp and other end of lamp connect to positive supply
- Connect On/Off switch from positive supply of circuit to +6V battery and connect the negative of 6V battery to GND.
- Connect positive of capacitor C2 to positive supply of the circuit and negative of C1 connect to GND.
Conclusion:
This PWM Based Lamp Brightness Controller Circuit for controlling brightness uses very little power and can change how bright a lamp is by using PWM control.
By changing the duty cycle with resistor R2 people can easily adjust the brightness.
This simple and energy saving circuit is great for small lighting needs, helping to lower power use while keeping the light at just the right level.