china pcb manufacturers to Timer Ciruits Can Help You Out

Timer Ciruits Can Help You Out 555 timer circuits have been used by enthusiasts and professional designers to solve the problem of finding a source of timing in digital applications. Since it was introduced in the early seventies, many thousands of standard designs have been built into readily available libraries that can be found on the Internet.

Housed in an eight pin chip, the device can be powered from a wide range of supply voltages. Also available in a dual version, the 556 is a fourteen pin chip, saving space on your PCB if you have dual timer applications. The basic timing circuit configurations you'll find are astable (also known as free running), monostable, and bistable multivibrators.

Used in its astable mode, a multivibrator is simply an oscillator, giving an output that switches between low level and high level. This switching occurs at a frequency determined by timing components in the form of resistors and capacitors and it is often used to provide a clock signal for digital processing devices. The duty cycle, or ratio of high to low time is also set by similar components. The clock can also be used for timing in communications ports.

A multivibrator that is stable in one state only is known as a monostable. Once it's in its non stable state, it will go back to its stable state automatically and stay there until the next time it's triggered. This gives a single pulse of a predetermined time. Also known as a one shot, the monostable could be used to allow a fixed amount of liquid to flow through a pipe, by controlling a valve.

Cheap bistables are available in single packages, so it it often more cost effective to use those rather than having to add external components, when the timing aspect is probably not relevant. A bistable device can be triggered from its current state to the other state, so it can be used as a simple single bit memory device, often called a flag.

Sound oriented projects can make good use of the triple five device if the output is one or more musical notes. The selected frequencies, determined by the choice of capacitors and resistors, can produce an audible sound if sent to a speaker. If several switches are used to connect different values of capacitor and resistor to the circuit, this could result in a simplified keyboard that could be operated by a small wand.

555 timer circuits make excellent switch debouncing devices. To prevent the switch bounce effect, which occurs when a switch is operated, the timing device is used to wait until the switch contacts have stopped vibrating and the final, correct value has stabilized. This prevents the possibility of an erroneous value being returned from the switch.

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