555 Timer Flashcards
The 555 timer is a circuit that provides what?
The 555 timer is a circuit that provides timing signals to other digital circuits.
Without accurate timing, everyday appliances such as TVs, VCRs, stereos, and even cars would not be able to function.
Most 555 integrated circuits are housed in hat type of case?
Most 555 integrated circuits are housed in an eight-pin dip case.
The major components of the 555 timer are what?
The major components of the 555 timer are an inverter, a transistor, 2 comparators, and an RS flip-flop.
What is the purpose of this component?
A comparator that compares two input voltage levels.
The – input is subtracted from the + input. If the difference is positive, the output is ______. If the difference is negative, the output is ______. Notice that, in this case, the input is an analog voltage and the output is a digital level.
The – input is subtracted from the + input. If the difference is positive, the output is HIGH (1 or true). If the difference is negative, the output is LOW (0 or false). Notice that, in this case, the input is an analog voltage and the output is a digital level.
If the S (SET) input is HIGH, Q is HIGH and Q is LOW. The flip-flop is said to be _____.
If the S (SET) input is HIGH, Q is HIGH and Q is LOW. The flip-flop is said to be SET.
If the R (RESET) input is HIGH, Q is LOW and Q is HIGH. The flip-flop is _____.
If the R (RESET) input is HIGH, Q is LOW and Q is HIGH. The flip-flop is RESET.
Having R and S HIGH at the same time will drive both Q and Q _____, which is an ______ condition.
Having R and S HIGH at the same time will drive both Q and Q LOW, which is an invalid input condition.
Once the flip-flop is SET or RESET, the outputs will not change if the inputs become zero.
The flip-flop stays SET or RESET until a _____ is present on an ______.
Once the flip-flop is SET or RESET, the outputs will not change if the inputs become zero.
The flip-flop stays SET or RESET until a HIGH is present on an input.
The ____ input overrides inputs R and S. If CLR is LOW, the flip-flop resets (Q LOW and Q HIGH), even if input S is HIGH.
The CLR input overrides inputs R and S. If CLR is LOW, the flip-flop resets (Q LOW and Q HIGH), even if input S is HIGH.
The CLR input overrides inputs R and S. If CLR is _____, the flip-flop resets (Q LOW and Q HIGH), even if input S is HIGH.
The CLR input overrides inputs R and S. If CLR is LOW, the flip-flop resets (Q LOW and Q HIGH), even if input S is HIGH.
What is the purpose of this symbol?
A comparator
It compares two input voltage levels.
If the + input is more positive than the – input, the output is _____.
If the + input is more positive than the – input, the output is HIGH (1 or TRUE).
If the + input is less positive than the – input, the output is _____.
If the + input is less positive than the – input, the output is LOW (0 or false).
The small circle on the CLR input indicates what?
That a LOW activates this function.
Explain why the RS flip-flop SET or RESET
Reset because a LOW on the CLR input overrides a HIGH on inputs R and S.
The R and S inputs to the flip-flop are provided by what?
the outputs of two comparators.
What determines if the flip-flop will SET or RESET?
Depending on which comparator has the HIGH output.
Will a zero or LOW input to the RS flip-flop have an effect?
A zero or LOW input to the RS flip-flop has no effect. The flip-flop stays SET or RESET.
The CLR input to the flip-flop would come from where?
The CLR input to the flip-flop comes from an external source. In most configurations, the CLR input is tied to Vcc, which disables CLR.
