555 Timers and Filters Flashcards
What is a 555 timer?
An IC that is used in a variety of timer, pulse generation and oscillator applications.
What are the output ranges for the 555?
Frequencies of up to 3MHz and currents up to 200mA which is more than a lot of IC’s so allows the 555 to run output transducers directly.
What are the main features of a 555 internal circuit?
3 5k resistors. a SR flip flop, along with two comparators, finally a transistor that acts as a switch.
What is a FlipFlop?
A circuit that has two stable states and can be used to store the information of the state of the circuit.
What is the Monostable mode of operation?
An external trigger creates a single pulse of adjustable duration. The output of the circuit will stay in the low state until there is a trigger input. Monostable means there is only one stable state.
What are the uses of the Monostable 555?
Creating Time delays, producing bounce free switches and touch switches. For example a person at an exhibit can push a button to start the models mechanism moving. Thus the mechanism will automatically switch off after a set time.
What is the Bistable mode of operation?
The timer has two stable states, high and low. Making the trigger input go to low will make the output go into a high state. Having the reset input low makes the Output go into the low state.
What are the uses of the Bistable mode of Operation?
Something like a quiz system. Each participant has a trigger push switch that lights a LED, then a reset push switch can cancel the LED to get ready for the next question.
What is Pulse Width Modulation?
A modulation technique is used to encode a message into a pulsing signal. Modulation is the process of varying one or more properties of a periodic waveform with a modulating signal that contains information to be transmitted. The main use of PWM is to allow the control of the power supplied to electrical devices like a motor.
What is the Duty Cycle?
It is the amount of time that a waveform is in a high state.. So a 50% duty cycle means that the waveform is high 50% of the time.
