How do I use these two resistors R3, R4, and R5?

1774315354

How do I use these two resistors R3, R4, and R5? [Copy link]

What are the three resistors R3, R4, and R5 used for? How do you calculate the current of an LED lamp?

bioger

R3 and R4 can control the transistor switch, and R5 controls the current of the lamp. The current of the LED is the power supply voltage divided by R5.

1774315354

bioger published on 2017-12-18 08:07 R3 and R4 can control the transistor switch, and R5 controls the current of the lamp. The current of the LED is the power supply voltage divided by R5

May I ask, do R3 and R4 correspond to the resistance values of R2 and R1 mentioned above?

bioger

1774315354 Published on 2017-12-19 09:41 Do R3 and R4 correspond to the resistance values of R2 and R1?

They don't correspond. The former controls the output of 555 and the latter controls the transistor.

gaon

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