A light control circuit is designed with photosensitive resistor and LED, which requires lLED to glow when dark and LED… when bright.
“Light” dark day 10m daytime 1K, and 10K partial voltage, through the operational amplifier lm358 voltage comparison, so that the transistor on or off, control lamp on and off, the picture assumes that the led is a small led,vcc voltage is 5V.
The current-limiting resistor is used to power the LED when it is bright, and the LED is slightly bright, and when it is dark, the comparator acts to make the LED get a large current and become brighter.
In the case of light, the resistance of the photosensitive resistor is only a few Ω ~ dozens of Ω, the base of the transistor Q1 is low voltage, and the transistor Q1 cannot be turned on, so the base of the PNP transistor Q is high voltage and cannot be turned on, so at this time, LED will not glow.
The simplest realization method is to use 555 connected to the non-steady-state circuit to drive the LED, the non-steady-state circuit is adjusted to the low-frequency oscillation state, and the photosensitive resistor is connected between the power supply Vcc and the 5-pin. When the light becomes weak, the resistance becomes larger, the 5-pin potential decreases, the non-steady-state oscillation frequency increases, and the LED flash frequency naturally increases.
I use single-chip microcomputer to control the brightness of LED lamp, how to design the control circuit? Why use a transistor?
1. The base of the transistor is connected with the I-stroke O port of the single-chip microcomputer, the collector is connected with the LED and the current-limiting resistor, the power supply, and the emitter is grounded, so that the LED can be well driven, but it is better to control the brightness of the LED with PWM.
2. The led lamp can be operated directly through IO port. If the power consumption of the led lamp is very high and large current is needed, the transistor can be used, and the IO port at this time is the switch.
3. Q1 plays the role of switch, the base of Q1 is low level, which turns on LED, while Q4 plays the role of inverting phase, and the base signal of Q4 is high voltage, which makes Q1 turn on, so that the PWM positive pulse signal sent by single-chip microcomputer can be easily controlled by LED lamp.
4. If you want to use single-chip microcomputer to control the brightness of external LED lamp, you need to use PWM driver, and use the duty cycle of PWM to drive the external power to adjust the transistor.
Ten points for attention and three Design ideas for Interior Lighting Design of LED Lamp
In the design of lamps and lanterns, it is necessary to ensure that the light source has a reliable electrical connection, the contact resistance is small, and will not be loosened after vibration. In order to protect the light source and prolong the life of the light source, the internal structure of the lamp must be scientific and reasonable.
Led lamps and lanterns design precautions do not use bipolar power devices experts pointed out that because bipolar power devices are cheaper than MOSFET, generally about 2 cents, so some designers use bipolar power devices in order to reduce the driving cost of LED, which will seriously affect the reliability of the circuit.
Basic rule: the main light source is best to see only light, no light source. The light source is exposed to the outside, not to mention the ash, but also easily affect the overall soft deployment. Useful criteria: all kinds of cabinets must have internal lighting system, wardrobes, cabinets, bathroom cabinets and so on.
What is the circuit design of the LED light belt?
The main results are as follows: 1. The advantage of series circuit is that the current is constant and it is easy to control the driving current of LED. The disadvantage is that if one of the LED is damaged, all LED will not light up, but will not affect the life of the other LED.
2. The circuit diagram of LED lamp strip usually consists of LED lamp beads, resistors, capacitors and power supplies. Among them, the LED lamp bead is the core component of the LED lamp strip, which is responsible for luminous. Resistors and capacitors are used to stabilize the current and filter voltage. The power supply is the energy source of the LED lamp strip, usually using DC power supply.
3. How is the circuit of led desk lamp? when the led desk lamp is working, that is, when it is on, the parameters involved are IF, VF, and the other parameters are brightness, efficiency, color, slope length, color temperature, power consumption and so on.
4. Finally, the LED light switch is turned on for testing, and it is found that the LED light is on and the wiring process is correct. First find out whether the lamps and lanterns use high voltage or low voltage electricity. Normally, the lamp belt will be equipped with low voltage electricity in consideration of safety. Led lamp has the advantage of high efficiency and energy saving. The working voltage of LED is low and DC drive mode is adopted.