**Simple LED Desk Lamp Dimming Circuit Diagram (1)**
This energy-efficient LED desk lamp circuit uses a combination of 1W high-power LEDs and φ5mm low-power LEDs. It features a unique trigger dimming circuit, making it simple in design and easy to implement. The circuit utilizes an operational amplifier for control, and the brightness is comparable to a 25W incandescent bulb. It is energy-saving, reliable, and has a long lifespan.
The power supply is derived from a transformer T followed by a bridge rectifier D1–D4, converting 220V AC to 14V DC. Operational amplifier A1 and regulator IC1 provide a reference voltage for A2. Resistors R3–R6 set the non-inverting input of the flip-flop circuit, while resistor R9 samples the inverting input. The output pulse width is adjusted using a potentiometer RP, amplified by transistors BG1 and BG2, and used to drive the LEDs. A freewheeling diode D5 and inductor L1 help smooth the current.
The components include a 8W 9V transformer, 24 φ5mm LEDs, and two 1W high-power LEDs with heat sinks. The op-amps are LM358 or LM324, and the regulator is TL31. The inductor L1 is wound with 40 turns of 0.25mm enameled wire on a φ15mm core. Resistor R9 is 2.2Ω–3.0Ω, rated at 1W.
After power is applied, the capacitor C1 should show 14V DC, dropping to about 10.5V under full load. The LED current is controlled by R9, ensuring that the 1W LEDs receive at least 350mA. Each φ5mm LED operates at less than 20mA, and a 20Ω resistor can be added in series to maintain proper current levels. A power switch is recommended for the mains input.
**Simple LED Desk Lamp Dimming Circuit Diagram (2)**
This basic dimming circuit uses a potentiometer to adjust the brightness of white LEDs. Multiple groups of LEDs can be connected in parallel for different lighting effects. One group can function as a night light, while others can be used for reading or general illumination.
Adjusting the potentiometer changes the brightness, but the dimming effect may not be very noticeable if the resistance is too low. A CZ socket can be used to test the circuit with a soldering iron, allowing the LED brightness to indicate temperature. This setup can also be used with an LED board as shown in Figure 2, where adjusting the potentiometer enables dimming functionality.
Figure 2 shows a small LED array made from high-gloss white LED panels. The board is 146mm long and 16mm wide, containing 8 LEDs per board. Seven such boards were used to create a larger LED array, powered by 12V. It’s a cost-effective, energy-saving solution suitable for nighttime use or reading.
**Simple LED Desk Lamp Dimming Circuit Diagram (3)**
A 12V LED dimming circuit is shown in the schematic, providing a straightforward design for controlling LED brightness.
**Simple LED Desk Lamp Dimming Circuit Diagram (4)**
This circuit uses a CD4017 counter IC to create a sequential dimming effect. It’s ideal for applications requiring a gradual change in brightness.
**Simple LED Desk Lamp Dimming Circuit Diagram (5)**
This design uses a transistor-based driver circuit. Transistors act as current controllers, amplifying the signal to drive the LEDs. The SS8550 PNP transistor is used to drive 12 LEDs in series and parallel, offering a low-cost and easily adjustable solution.
LED brightness is controlled by current, and the formula I = LI represents the average current. By adjusting the PWM duty cycle, the current can be varied, thus controlling the brightness. In this design, the STC89C51 microcontroller outputs a PWM signal through pin P1.3. When the signal is high, the transistor Q1 allows a small current; when low, it allows a larger current. This variation in average current controls the overall brightness of the LED lamp.
**Simple LED Desk Lamp Dimming Circuit Diagram (6)**
This final diagram presents a complete layout for an LED desk lamp with dimming capability. It includes all necessary components for a functional and efficient lighting system.
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