Can 1N4007 diode be used as the current limiting resistor of white light diode for rechargeable flashlight If there are 14 white light diodes, can only one 1N4007 diode be used as current limiting resistor? The voltage of flashlight lead-acid battery is 4.2V, and the voltage of LED bead circuit is 3.2V with a 1N4007 diode in series

Can 1N4007 diode be used as the current limiting resistor of white light diode for rechargeable flashlight If there are 14 white light diodes, can only one 1N4007 diode be used as current limiting resistor? The voltage of flashlight lead-acid battery is 4.2V, and the voltage of LED bead circuit is 3.2V with a 1N4007 diode in series

1N4007 is a rectifying diode. Like other diodes, its characteristic curve is nonlinear, and its current limiting effect is worse than resistance. It is better to build a simple constant current source circuit to limit the current

How much resistance should two LED beads be connected to 12V power supply? How about three?

Resistance R = u / I is calculated in ohm, voltage in volt and current in ampere. If current is in Ma, it is calculated in kiloohm
Where, u = power supply voltage LED voltage, generally red and yellow power supply voltage 1.2V, green and blue power supply voltage 3.3.5v, if you use 12V power supply, several LEDs in series, you need to add together
I is the current. It depends on the number of LEDs in parallel. If it is only one group of LEDs, it is generally considered that 18 ~ 20mA is enough (0.02A)
In addition, the power of the resistor can be calculated according to the current and voltage

LED connected to 220 V
There are two LEDs
Voltage of red LED: 1.9-2.1 V
Voltage of blue LED: 3.2-3.4 V
Their current is 15-20ma
The power supply should be connected to 220 v
How many ohmic resistors are connected in red and blue, and what is the diode used

Four 1N4007S can be used as bridge rectifiers and 12K 2W resistors can be connected in series. Red and blue can have the same resistance value without calculation;
In addition:
The red LED can be directly connected with a 12K resistor in series to connect with the commercial power;
It is better to connect two anti phase parallel resistors in series with the commercial power in blue, because blue is easy to break down;