How to Use the Mobile Phone Charger As the Power Supply to Add an Optical Control LED Lamp to the Wa

The figure above shows a simple light controlled LED lighting circuit composed of two 9014 triodes. RG is a cadmium sulfide photoresist, which is used to detect the intensity of light. Triodes Q1 and Q2 form an electronic switch to control the operation of white LED beads.

When there is light in the room during the day or at night, due to the small resistance value of RG, triode Q1 is saturated and turned on, its collector voltage is ≤ 0.2V, and Q2 emitter junction voltage is the same as Q1 collector voltage, so Q2 is cut off, and the white LED bulb is not on. When the indoor light is turned off at night, the RG resistance becomes large, Q1 is cut off, and the clamping of Q2 base voltage is lost, so that Q2 is turned on and the LED bulb is lit.

When making, RG can select the photoresist shown in the figure above, and it is better to select the photoresist with larger dark resistance to reduce the static power consumption of the optical control circuit.

For the LED lamp beads used for lighting, the in-line high brightness white LED lamp beads shown in the above figure can be selected. The brightness of the lamp bead can be adjusted by the resistance R4 in the circuit in Figure 1. The smaller the resistance value of R4, the higher the brightness of the LED lamp bead. However, it should be noted that the resistance value of R4 should not be too small to avoid excessive current flowing through the lamp bead and damaging the lamp bead.

By adjusting the resistance value of R2 in the circuit in Figure 1, the LED bulb can be lit under the required light. Triode Q1 and Q2 are 9014 triodes, which are required to β ≥300。 The entire optical control circuit can be powered by a 5V mobile phone charger.