3 If you want to connect a 7 volt LED to a 12 volt battery, how to connect it, and how big a diode o

You didn't give the most critical parameter of the LED - the current value. Because LEDs are current elements, voltage is only a reference value.

Let's assume that the LED operating current is 30mA. (If there is a difference, please calculate it as follows).

If an LED is connected to a 12V voltage, it must be eaten by a step-down diode or current-limiting resistor. Because each forward voltage drop of silicon diode is 6V, it needs to be connected in series a lot to achieve the purpose, so it is not considered to be used.

The following calculation uses resistance to step down.

The resistor needs to be stepped, and the current flowing through is the same as that of the LED, that is, 30mA, so r=ohm, you can choose a 300 ohm resistor. Conversely, check the actual current using a 300 ohm resistor: i=v r=ohms=27mA. It's a little lower than the rated current (3mA), but it doesn't affect the brightness, it's totally fine.

Find the withstand power value of the resistor = v*v r = 8,3 x 300 =, and the resistance of a quarter watt can be selected.

Summary: A 300 ohm quarter watt resistor can be stringed, and the LED current is 27mA.

, resistance value = value 300 is appropriate.

The 24V LED lamp cannot be directly connected to the 12V battery, and the voltage will not light up if the voltage does not match, so you need to buy a 12V to 24V power converter to convert the voltage before you can connect the 24V lamp.

Each LED needs to provide a certain voltage of DC power supply to light up (the power supply voltage should be higher than its on-voltage), the power supply provided by the power converter can also become the power supply of the LED through a certain rectifier device, so that the LED can emit light normally (like the indicator light on most power strips), the power supply voltage is lower than its on-voltage, at this time, the LED will not light up at all because the voltage is not enough, the current is cut off.

LED lights are not like ordinary incandescent lamps, and the filament voltage is a little lower and you will see red light.

Solution: Buy a 12V to 24V power converter to convert the voltage, and the voltage can be lit up when the voltage reaches the 24V required for the LED light.

Power converter function:

The location of the power supply to the on-board electrical appliances in the car's electrical system. Its power comes from batteries, which are used to power on-board appliances, and its important function is to provide power for power steering, air conditioning and other auxiliary equipment. The other type is in the composite power supply system, which is connected in series with supercapacitors to regulate the power output and stabilize the bus voltage.

The negative electrode of the light-emitting diode is connected to the negative pole of the 12V battery, the positive electrode of the light-emitting diode is connected in series with a 3,000 ohm 5,000 ohm resistor, the LED current is controlled at 4mA 2mA, and the resistance is connected to the positive pole of the battery.

LEDs cannot be connected directly to the power supply when they are used. Generally, according to the model of the light-emitting diode, the size of the current limiting resistor, 12 volts and 24 volts can be lit, but it will burn immediately after being connected.

It is recommended to connect a current-limiting resistor on the LED pins, and find a way to control the voltage at both ends of the LED at about 2 volts.

Ordinary light-emitting diodes. Take 470k 1 4W resistor, tens of K resistors will burn out because of excessive power. If you want a higher current, you can't use a resistor, use a CBB capacitor to step down in series, and a 1UF return section to provide 55mA current.

Take into account the characteristics of the capacitance. The voltage does not change at the moment of power-on, so the use of capacitor step-down requires bridge rectification and CRC filtering. This circuit does not generate heat, provides high current, and is highly efficient.

It has been widely used in LED lighting.

Hello, the voltage mismatch will not light up, or buy an extra battery in series to use, another way is to buy a 12V to 24V converter upstairs.

A 12V to 24V converter needs to be purchased.

One adjustable resistor (to adjust the current of the LED), one LED, one switch, and one ammeter (to measure the current of the LED).

1. First, install the current limiting resistor on the negative pole of the power line.

2. Then separate the positive and negative pole lines of the LED strip.

3. Use a peeler to remove the positive wire of the LED strip.

4. The positive line of the LED lamp after peeling. This is shown in the figure below.

5. Connect the negative wire of the power supply with the positive wire of the LED strip.

6. Then connect the negative lead of the LED with the current limiting resistor.

7. After completing the above steps, the wiring of the version of the LED light is completed.

8. Finally, turn on the LED light switch for testing, and find that the LED light is on, and the wiring process is correct.

Because the power supply of LED lights is 3-5V. So you can do the following without adding any components:

1. Every three LED lights are connected in series as a group.

2. A total of 10 groups are connected in series.

3. Connect 10 groups in parallel.

The 1W LED is generally about VF and the current is 350mA, so it can be like this: every 3 series in series as a group, a total of 10 groups, and these 10 groups are connected in parallel.

Because LED and brightness and life are directly related to its power supply current, so can not be directly connected to the battery, need the corresponding constant current drive, here I recommend using AMC7140 to drive, this chip input voltage 5-50V, can constant current output 0-750mA (according to RSET to set), you can use 1 chip to set 700mA output, to drive 2 groups of parallel LED strings, so you need 5 drives, but this method has a problem, When one of the 2 parallel strings is open, the 700mA current will all go to the other group, and the other group will be burned directly, this problem can be used with 10 drivers to drive each 3x1W LED string separately, but the cost is slightly higher than the previous one.

If it is a direct series resistor, connect it according to the connection method on the figure, so that the current is about 280mA, and the power consumption of the resistor is about, so the 2W resistor is selected to reduce the heat.

If the LED is calculated according to 3V, then 3 LEDs are 1 string, and then a 1W10 ohm resistor, so a total of 10 strings, 10 strings are connected in parallel to 12V, and the actual power of each LED is watts, which is a more secure connection.

However, the heat generation of LEDs and resistors is relatively large, so pay attention to heat dissipation.

Look at how big the current and voltage of your lamp is.

If it's 12V, you have to string 144R resistors and then connect them in parallel.

Here's how:

1. The negative pole of the light-emitting diode is connected to the negative pole of the 12V battery.

2. The positive electrode of the light-emitting diode is connected in series with a 3 thousand ohm to 5 thousand ohm resistor.

3. The LED current is controlled at 4mA 2mA.

4. The resistance of the light-emitting diode is connected to the positive pole of the battery.

The voltage of an ordinary diode drops in.

to around 3V. You just pick a middle zhi

Click on it, and it's very bright. A working version of the diode.

The current can be selected as 5 milliamperes, and the working current is too large, and the light decay will be added. (Since you're three LEDs, the current counts as 15 milliamps, which translates to 700 ohms.) The voltage after the motorcycle starts is not much, after all, the working current we choose is small, if you are worried, add a 50 ohm resistor to try.

But I don't think it's necessary... Give it to me, we have it at home, you can find me.

A 100 ohm or so resistor is connected in series.

No, it must be connected to the DC constant current source, otherwise it will either burn out quickly, or the brightness will be very low.

LED is a light-emitting device made of semiconductor materials to directly convert electrical energy into light energy and electricity signal into optical signals. It is characterized by low power consumption, high brightness, bright colors, vibration resistance, long life (normal light emitting 8-100,000 hours), cold light source and other advantages.

The battery is a battery that can be used after being charged, including lead-acid batteries, nickel-iron batteries and nickel-cadmium batteries. The positive electrode of the lead-acid battery is lead dioxide, the negative electrode is lead, and the electrolyte is a dilute sulfuric acid solution. When discharging (using), the positive and negative electrodes react with sulfuric acid to form lead sulfate, and when the concentration of sulfuric acid solution drops to a certain level, it must be charged.

When charging with an external power source, the electrode limb and solution can be restored to their original state, and they can be buried and continued to be used after charging.