LED PCB Circuit schematic

                                                                           LED  PCBCircuit schematic

LED indicator circuit diagram (1)

There are only two components in the circuit shown in Figure 1. R uses 1/6--1/8W carbon film resistor or metal film resistor, and the resistance value is between 1--300K.

Ne is a neon bulb, and the neon bulb in an ordinary fluorescent lamp starter is also selected. If you want to use a neon bulb that is small in size and can be started at about 60V, its model is NNH-616, and the resistance R is 1/270K. 6W metal film resistors. led indicator circuit:

LED indicator circuit diagram (2)

A transformer is used to convert high voltage to low voltage, and rectification and filtering are performed to output stable low-voltage direct current. The switching constant current source is divided into isolated power supply and non-isolated power supply. Isolation refers to the isolation of high and low output voltages, which is very safe, so the requirements for the insulation of the shell are not high. Non-isolated safety is slightly worse, but the cost is relatively low. Traditional energy-saving lamps use non-isolated power supply and are protected by insulating plastic shells. The safety of the switching power supply is relatively high (generally output low voltage), and the performance is stable. The disadvantage is that the circuit is complicated and the price is high. The switching power supply technology is mature and the performance is stable, and it is the mainstream power supply of LED lighting at present.

Figure 1: Switching constant Circuit schematic isolated fluorescent tube power supply

Figure 2: Schematic diagram of switching constant current isolated power supply

Figure 3: Switching constant current source power supply

LED indicator circuit diagram (3)

There is a cheap LED flashlight on the market. The front end of this flashlight is 5 to 8 high-brightness light-emitting tubes, and it uses 1 to 2 batteries. Due to the use of ultra-high-brightness luminous tubes, the luminous efficiency is very high, and the working current is relatively small. The measured current is only about 100mA using a 5-head flashlight with one AA battery. Very power saving. If you use a large-capacity rechargeable battery, it can be used continuously for more than ten hours, so I bought one. After being disassembled from the front end, the circuit diagram was drawn according to the actual object, as shown in the figure.

working principle:

After turning on the power supply, VT1 is connected to the negative pole because of R1, and the voltage at both ends of c1 cannot change abruptly. VT1 (b) pole potential is lower than e pole, VT1 is turned on, VT2 (b) pole has current flowing in, VT2 is also turned on, the current flows from the positive pole of the power supply through L, VT2 (c) pole to pole e, and flows back to the negative pole of the power supply. The power supply charges L, and L stores energy, and the self-induced electromotive force on L is positive on the left and negative on the right. Through the feedback of c1, the base potential of VT1 is lower than the emitter potential, VT1 enters a deep saturation state, and VT2 also enters a deep saturation state, that is, Ib>Ic/β (β is the magnification factor).

As the power supply charges c1,RF circuit board design the voltage across C1 gradually increases, that is, the VTI (b) electrode potential gradually increases, and Ib1 gradually decreases. When Ib1<=Ic1/β, VT1 exits the saturation zone, and VT2 also exits the saturation zone , the charging current to L decreases. at this time. The self-induced electromotive force on L becomes negative on the left and positive on the right, which is fed back by c1. The base potential of VT1 further rises, VT1 cuts off quickly, and VT2 also cuts off, the energy stored on L is released, and the power supply voltage on the light-emitting tube is added to L to generate a self-induced electromotive force to achieve the purpose of boosting voltage. This voltage is enough to make the LED glow.

LED indicator circuit diagram (4)

This circuit is an LED color-changing light control circuit suitable for landscape lighting such as city streets, parks and factory lighting projects. The circuit structure is simple, the service life is long, the light color is gorgeous, soft and beautiful.

The working principle is as follows: the circuit is energized, and the AC 220V is rectified, and one path is filtered by resistor R1 step-down C1 to generate +5V voltage to supply power to the integrated block U1 (12C508A); the other path is directly supplied to the anode of the light-emitting diode (red, green, blue) . When 12C508A is powered on, it will output 0~0.76V pulse signal from pin ⑤, pin ⑥ and pin ⑦ in turn, triggering the conduction of the corresponding thyristor, so that the connected light-emitting diode strings will emit light. The resistor R4 and capacitor C3 connected to pin ④ of U1 are controlled by time constant (changing the corresponding resistor and capacitor capacity specifications can change the lighting time of each string of LEDs); R2 and R3 are used to start the 12C508A when it is powered on . The normal cycle of the light is about 2 minutes.

The entire light string consists of 12 light panels with a width of 15mm and a length of 465mm, consisting of a total of 528 LEDs, and the red, green, and blue LEDs are arranged at intervals. Among them, the red LED is a string of 80. A 1.2kΩ/1W current-limiting resistor (current 13.7mA) is placed in 20 strings. Green and blue are 48 LEDs each. Each interval is 12 strings and a 1KΩ/1W resistor (the current is 15mA). Mix and cross arrange 44 as a set of boards.

Common faults: No light after power on. The fault is generally R2, R3, R1 open circuit or 12C508A damage. If there is a group of colors that are always bright, it means that the thyristor (MCR100-6) controlled by this group has broken down. Another most common phenomenon is that one of the light-emitting diode series circuits is aging or blown out, then the group will have no current flow and will not light up. At this time, you need to use a set of 3.0V power supplies, and connect a 20Ω in series. After the resistor. The group of diodes is searched one by one from the beginning to the end respectively. Just replace the LED that doesn't light up.

When repairing, be sure to disconnect the power supply before welding or finding faults. be safe. The circuit diagram drawn in kind is shown in the accompanying drawing.

LED indicator circuit diagram (5)

The circuit diagram of the led drive power supply is as follows

Input rectification part: Analyze the specific parameters of the high-voltage input rectification circuit, and then select the specifications of the specific insurance rectifier diode. Because our power is relatively low, we can choose wire-wound resistors as insurance. Use 1N4007 as the rectifier tube. If the power is large, you should choose other resistance current higher rectifier diodes.

Rectification and filtering part: If the EMI requirements are strict, the following π-type circuit can be added. If the requirements are not so strict, only one filter capacitor can be used. The specific capacity and inductance of the capacitor and inductor are selected according to the total power.

Drive circuit part: the current through R3 is converted into voltage, fed back to the IC to control the output current, and a DRC absorption circuit is added to the primary winding. Because we have a built-in mos tube, the drive circuit has been integrated in the IC circuit, so the drive mos circuit will not be explained. .

IC power supply and peripheral circuit part: through the auxiliary winding rectification and filtering, the IC is powered separately, and the output no-load voltage is controlled by the ratio of the resistance of R5 and R6.

Output rectification and filtering circuit part: through ultra-fast recovery diode rectification and high-frequency low-resistance electrolytic filtering, output to the load, and RC circuit filtering is added to the ultra-fast recovery diode, and the resistance and capacitance are selected through ultra-fast recovery diode reverse waveform debugging , to suppress the reverse peak of the diode at the maximum, add a false load at the output end, the general design of the false load will consume 3 mA of current.

LED indicator circuit diagram (6)

The circuit of this device is shown in the figure. It is mainly composed of a single power supply and low power consumption operational amplifier integrated circuit IC1, two low power transistors, a microphone and a high brightness light emitting diode. When the microphone MIC receives a certain intensity of external sound (including various noises), it generates an output voltage of corresponding intensity, which is added to the comparator IC1c. When the voltage exceeds the threshold value of the comparator, its output is a high potential, which turns V1 on. Its output voltage is added to the comparator IC1b. Similarly, this voltage device is higher than the threshold value of IC1b. IC1b outputs a high potential to excite the power amplifier composed of IC1a and V2, thereby driving the LED to emit light. The preset delay length. It is determined by the time constant of the charging and discharging circuit composed of C2 and R6, and R7 and R8.

On this illuminating device, also can add a button switch to make LED light up, and continue to shine at predetermined time. The power supply of the circuit is also very convenient, using 4 Ni-MH (MiMH) power supply. The whole device works intermittently, the battery can be used for 2 months, the whole circuit is in standby state, consumes 400μA of current, and consumes 24mA of current when the LED is on.

From the perspective of the circuit structure, the microphone MIC is connected between the input terminal and the ground wire through a wire. It is connected to the positive pole of the power supply through R1, and the AC component of the signal is coupled to the non-inverting pin of the operational amplifier IC through the capacitor C1. The adjustment of microphone sensitivity depends largely on the value of R1. It is recommended that the value of R1 be 15kΩ. For different brands and models of microphones used, the value of R1 should also be changed accordingly in order to achieve the desired sensitivity. When the maximum sensitivity is adjusted, the LED should be triggered and light up under the pressure of the air flow on the microphone diaphragm when the door is opened. IC1 adopts TLC274, and its pin diagram is shown in the figure.

LED indicator circuit diagram (7)

Buy a 1W white LED, try it with a mobile phone battery, it is really bright, you can make a small desk lamp.

Use creamy plastic bottle caps in the shape of wine glasses as lampshades. Lead out the positive and negative wires from the back of the LED cooling plate (included), pass through the lampshade, and lead into the lamp holder through the elbow. The shape of the lamp came out. For the convenience of charging, a solar panel is used, but the voltage is too low, and only one battery can be charged, so a booster board is added. In order to use in rainy days, AC charging is added, and LED lights can be lit under the condition of AC power supply. The terminal voltage of this LED is 3+2V, and the rated current is 350mA. After experiments, the voltage can still work normally when the voltage reaches 4.8V. The key The current limit is around 350mA.

The booster board is an oscillating circuit cut from the old board of the 6V emergency light without any modification (see the dotted line in the figure), and then provides charging current through bridge rectification. The author believes that oscillating circuits such as mosquito swatters, electronic igniters, and coin detectors can also be used as booster boards with minor modifications. The battery uses three AAA 1800mA.h Ni-MH batteries, and it can be charged in a bright place in the saddle without direct sunlight on the solar panel in summer. AC charging provides 4.3V charging voltage and about 350mA charging current. If you use three AA nickel-cadmium batteries, the current limiting resistor Ri should be changed to 8~iori to reduce the charging current and avoid damage to the battery.

LED indicator circuit diagram (8)

High-brightness white light-emittingdiodes (LEDs) are a popular lighting source because they are more energy-efficient than all other light sources. Here is a self-made LED dimming desk lamp. It does not use a dedicated IC or a single-chip microcomputer. It only needs a common digital circuit and a few discrete components to DIY a desk lamp with button dimming.