![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
How much resistance and power should 420 white bright LEDs be connected to 12V power supply? How many a should the power supply use? Is it OK to connect a resistor after all parallel connections? Current 20mA
In the streets of Beijing, there are a lot of LED decorations, just like stars, which are very beautiful. I have carefully observed that there is a resistor in series on each LED. Therefore, it can be judged that the LED is connected in parallel at both ends of the power supply. However, according to what you said, if there are 420 LEDs, it needs 420 * 20mA = 8.4a power supply. In this way, the power supply
How much resistance is needed to supply 12 3W LEDs in parallel with 12V
LED has different voltage according to different colors, which can be estimated as 3.6V
3W / 3.6V × 12 pieces = 10A current,
(12-3.6) V / 10A = 0.84 Ω
（12-3.6)V×10A＝84W
It can be seen that this is very unreasonable. The power consumption of step-down resistor is far greater than the total power consumption of LED. The correct way is to connect three LEDs in series and then four LEDs in parallel
Total current = 3W / 3.6V × 4 = 3.3a
Resistance = (12-3 * 3.6V) / 3.3a = 0.36ohm
Resistance power consumption = (12-3 * 3.6V) × 3.3a = 3.96w
Resistance can choose 5W cement resistance, if you can't find a suitable resistance value, try to take higher resistance value, don't take low, otherwise the current is too large, very affect the life of LED. In addition, the best use of regulated power supply, second-hand computer power supply is a very good choice, as low as 10 more than 20 yuan
RELATED INFORMATIONS
- 1. The input voltage is 12V. How much current limiting resistance is needed for parallel connection of two groups of circuits with four light-emitting diodes in series? How to calculate Led 3.3.6v 20mA
- 2. What is the resistance of a 1m long data line I want to use it to calculate the power loss of the wire at 1A current
- 3. As shown in the figure, on the horizontal plane, there are two smooth metal guides without resistance, which are parallel and fixed. The spacing D is 0.5m. The right end is connected with a small bulb l with resistance of 4 Ω through a wire. There is a uniform vertical magnetic field in the rectangular area of cdfe. The length of CE is 2m. The change of magnetic induction intensity B with time t in the area of cdfe is shown in the figure. When t = 0s, a metal bar with resistance of 1 Ω acts under constant force F When the metal rod moves from ab position to ef position, the brightness of the small bulb does not change______ N. The mass of the metal bar is______ kg．
- 4. If the arc AB is 1 / 3 of the circumference, what is the resistance between ab? If point a is fixed and point B is optional on the circumference, what is the maximum value of resistance between ab?
- 5. The internal resistance of the generator is r = 0.1 ohm, the load resistance is r = 22 ohm, the current in the circuit is I = 10a, and the resistance of each connecting wire is RL = 0.1 ohm What is the electromotive force of the engine What is the output power of the power supply What is the power of the engine
- 6. How to calculate the DC resistance of electric furnace wire? Well, under rated working conditions, what is the current of 220v3000w AC furnace wire? If you add 220V DC, what are the power and current? Inductance needs to be considered. Because I want to calculate and intercept a section of power for 110V discharge, up to 1000W.
- 7. If you use an electric stove to boil water, the electric stove wire turns red, but the copper wire connected to the electric stove wire is not very hot. Why?
- 8. "The hydraulic resistivity is 18.2m Ω. Cm", what does m Ω. Cm mean? What does cm mean?
- 9. What is the unit of resistivity and conductivity? How to calculate What's the difference between pure water conductivity and conductivity? What's their unit? How to calculate? M Ω. Cm help me to explain his unit name. And μ s / cm unit name explanation?
- 10. 3. As shown in the figure, I and II are the divergent rays of the light source s (not shown in the figure) on the principal axis PQ of the lens after being refracted by the lens. In the figure, l is the position of the lens, O is the optical center of the lens, and m is the intersection point of the opposite extension lines of the two rays () A. if the luminous point s is on M, the transparent mirror is a convex lens B. if the luminous point s is on the left side of M, If s is on the right side of M, the lens is convex D. lens L must be concave
- 11. How much current limiting resistor should this LED circuit be connected to? At present, a 5V / 4A power supply is connected to six ordinary LED lamp beads. The lamp beads need to be connected in parallel. How large is the current limiting resistance of each path?
- 12. What is the difference between the ammeter connection of two circuit diagrams in the volt ampere characteristic test of nonlinear resistance?
- 13. The function of constant resistance in circuit It is said in the book that the constant value resistance remains unchanged, and the relationship between voltage and current is measured. Then a constant value resistance (such as 5 Ohm) is selected and measured. My question comes. ① in the circuit diagram, the constant value resistance is connected in series, and the voltmeter is connected in parallel with the constant value resistance, but how to explain the constant value resistance when measuring the current? ② the constant value resistance is connected in series to the circuit, Is the resistance in the circuit the same as the constant resistance? ③ since the resistance is the physical quantity that hinders the current, why is the value of the ammeter after the constant resistance the same as that of the ammeter placed in the constant resistance when the current passes through the constant resistance I don't have a good head
- 14. Why does the current choose the one with small resistance
- 15. In the experiment to explore which factors are related to the resistance of conductor
- 16. The physical research method used in the experiment to explore the "factors determining the size of resistance" is______ When making conductor and resistance wire, it is mainly based on the characteristics of conductor______ It is selected according to the influence of resistance
- 17. Characteristics of resistance in series circuit and parallel circuit
- 18. Experimental steps and circuit diagram of measuring resistance by volt ampere method and safety resistance method (only one ammeter and one custom resistance are required)
- 19. The main steps of drawing circuit diagram and how to draw resistance
- 20. What does Chang'an and creative nature mean?